Getting Started link

This is a tutorial written by Ryan C Gordon (a Juggernaut in the industry who has contracted to Valve, Epic, Activision, and EA... check out his Wikipedia page: https://en.wikipedia.org/wiki/Ryan_C._Gordon).

Introduction link

Welcome!

Here's just a little push to get you started if you're new to programming or game development.

If you want to write a game, it's no different than writing any other program for any other framework: there are a few simple rules that might be new to you, but more or less programming is programming no matter what you are building.

Did you not know that? Did you think you couldn't write a game because you're a "web guy" or you're writing Java at a desk job? Stop letting people tell you that you can't, because you already have everything you need.

Here, we're going to be programming in a language called "Ruby." In the interest of full disclosure, I (Ryan Gordon) wrote the C parts of this toolkit and Ruby looks a little strange to me (Amir Rajan wrote the Ruby parts, discounting the parts I mangled), but I'm going to walk you through the basics because we're all learning together, and if you mostly think of yourself as someone that writes C (or C++, C#, Objective-C), PHP, or Java, then you're only a step behind me right now.

Prerequisites link

Here's the most important thing you should know: Ruby lets you do some complicated things really easily, and you can learn that stuff later. I'm going to show you one or two cool tricks, but that's all.

Do you know what an if statement is? A for-loop? An array? That's all you'll need to start.

The Game Loop link

Ok, here are few rules with regards to game development with GTK:

Your game is all going to happen under one function ...
that runs 60 times a second ...
and has to tell the computer what to draw each time.

That's an entire video game in one run-on sentence.

Here's that function. You're going to want to put this in mygame/app/main.rb, because that's where we'll look for it by default. Load it up in your favorite text editor.

def tick args
  args.outputs.labels << [580, 400, 'Hello World!']
end

Now run dragonruby ...did you get a window with "Hello World!" written in it? Good, you're officially a game developer!

Breakdown Of The tick Method link

mygame/app/main.rb, is where the Ruby source code is located. This looks a little strange, so I'll break it down line by line. In Ruby, a '#' character starts a single-line comment, so I'll talk about this inline.

# This "def"ines a function, named "tick," which takes a single argument
# named "args". DragonRuby looks for this function and calls it every
# frame, 60 times a second. "args" is a magic structure with lots of
# information in it. You can set variables in there for your own game state,
# and every frame it will updated if keys are pressed, joysticks moved,
# mice clicked, etc.
def tick args

  # One of the things in "args" is the "outputs" object that your game uses
  # to draw things. Afraid of rendering APIs? No problem. In DragonRuby,
  # you use arrays to draw things and we figure out the details.
  # If you want to draw text on the screen, you give it an array (the thing
  # in the [ brackets ]), with an X and Y coordinate and the text to draw.
  # The "<<" thing says "append this array onto the list of them at
  # args.outputs.labels)
  args.outputs.labels << [580, 400, 'Hello World!']
end

Once your tick function finishes, we look at all the arrays you made and figure out how to draw it. You don't need to know about graphics APIs. You're just setting up some arrays! DragonRuby clears out these arrays every frame, so you just need to add what you need _right now_ each time.

Rendering A Sprite link

Now let's spice this up a little.

We're going to add some graphics. Each 2D image in DragonRuby is called a "sprite," and to use them, you just make sure they exist in a reasonable file format (png, jpg, gif, bmp, etc) and specify them by filename. The first time you use one, DragonRuby will load it and keep it in video memory for fast access in the future. If you use a filename that doesn't exist, you get a fun checkerboard pattern!

There's a "dragonruby.png" file included, just to get you started. Let's have it draw every frame with our text:

def tick args
  args.outputs.labels  << [580, 400, 'Hello World!']
  args.outputs.sprites << [576, 100, 128, 101, 'dragonruby.png']
end

NOTE:

Pro Tip: you don't have to restart DragonRuby to test your changes; when you save main.rb, DragonRuby will notice and reload your program.

That .sprites line says "add a sprite to the list of sprites we're drawing, and draw it at position (576, 100) at a size of 128x101 pixels". You can find the image to draw at dragonruby.png.

Coordinate System and Virtual Canvas link

Quick note about coordinates: (0, 0) is the bottom left corner of the screen, and positive numbers go up and to the right. This is more "geometrically correct," even if it's not how you remember doing 2D graphics, but we chose this for a simpler reason: when you're making Super Mario Brothers and you want Mario to jump, you should be able to add to Mario's y position as he goes up and subtract as he falls. It makes things easier to understand.

Also: your game screen is _always_ 1280x720 pixels. If you resize the window, we will scale and letterbox everything appropriately, so you never have to worry about different resolutions.

Ok, now we have an image on the screen, let's animate it:

def tick args
  args.state.rotation  ||= 0
  args.outputs.labels  << [580, 400, 'Hello World!' ]
  args.outputs.sprites << [576, 100, 128, 101, 'dragonruby.png', args.state.rotation]
  args.state.rotation  -= 1
end

Now you can see that this function is getting called a lot!

Game State link

Here's a fun Ruby thing: args.state.rotation ||= 0 is shorthand for "if args.state.rotation isn't initialized, set it to zero." It's a nice way to embed your initialization code right next to where you need the variable.

args.state is a place you can hang your own data. It's an open data structure that allows you to define properties that are arbitrarily nested. You don't need to define any kind of class.

In this case, the current rotation of our sprite, which is happily spinning at 60 frames per second. If you don't specify rotation (or alpha, or color modulation, or a source rectangle, etc), DragonRuby picks a reasonable default, and the array is ordered by the most likely things you need to tell us: position, size, name.

There Is No Delta Time link

One thing we decided to do in DragonRuby is not make you worry about delta time: your function runs at 60 frames per second (about 16 milliseconds) and that's that. Having to worry about framerate is something massive triple-AAA games do, but for fun little 2D games? You'd have to work really hard to not hit 60fps. All your drawing is happening on a GPU designed to run Fortnite quickly; it can definitely handle this.

Since we didn't make you worry about delta time, you can just move the rotation by 1 every time and it works without you having to keep track of time and math. Want it to move faster? Subtract 2.

Handling User Input link

Now, let's move that image around.

def tick args
  args.state.rotation ||= 0
  args.state.x ||= 576
  args.state.y ||= 100

  if args.inputs.mouse.click
    args.state.x = args.inputs.mouse.click.point.x - 64
    args.state.y = args.inputs.mouse.click.point.y - 50
  end

  args.outputs.labels  << [580, 400, 'Hello World!']
  args.outputs.sprites << [args.state.x,
                           args.state.y,
                           128,
                           101,
                           'dragonruby.png',
                           args.state.rotation]

  args.state.rotation -= 1
end

Everywhere you click your mouse, the image moves there. We set a default location for it with args.state.x ||= 576, and then we change those variables when we see the mouse button in action. You can get at the keyboard and game controllers in similar ways.

Coding On A Raspberry Pi link

We have only tested DragonRuby on a Raspberry Pi 3, Models B and B+, but we believe it _should_ work on any model with comparable specs.

If you're running DragonRuby Game Toolkit on a Raspberry Pi, or trying to run a game made with the Toolkit on a Raspberry Pi, and it's really really slow-- like one frame every few seconds--then there's likely a simple fix.

You're probably running a desktop environment: menus, apps, web browsers, etc. This is okay! Launch the terminal app and type:

do raspi-config

It'll ask you for your password (if you don't know, try "raspberry"), and then give you a menu of options. Find your way to "Advanced Options", then "GL Driver", and change this to "GL (Full KMS)" ... not "fake KMS," which is also listed there. Save and reboot. In theory, this should fix the problem.

If you're _still_ having problems and have a Raspberry Pi 2 or better, go back to raspi-config and head over to "Advanced Options", "Memory split," and give the GPU 256 megabytes. You might be able to avoid this for simple games, as this takes RAM away from the system and reserves it for graphics. You can also try 128 megabytes as a gentler option.

Note that you can also run DragonRuby without X11 at all: if you run it from a virtual terminal it will render fullscreen and won't need the "Full KMS" option. This might be attractive if you want to use it as a game console sort of thing, or develop over ssh, or launch it from RetroPie, etc.

Conclusion link

There is a lot more you can do with DragonRuby, but now you've already got just about everything you need to make a simple game. After all, even the most fancy games are just creating objects and moving them around. Experiment a little. Add a few more things and have them interact in small ways. Want something to go away? Just don't add it to args.output anymore.

Starting a New DragonRuby Project link

The DragonRuby zip that contains the engine is a complete, self contained project structure. To create a new project, unzip the zip file again in its entirety and use that as a starting point for another game. This is the recommended approach to starting a new project.

NOTE:

It's strongly recommended that you do NOT keep DragonRuby Game Toolkit in a shared location and instead unzip a clean copy for every game (and commit everything to source control).

File access functions are sandoxed and assume that the dragonruby binary lives alongside the game you are building. Do not expect file access functions to return correct values if you are attempting to run the dragonruby binary from a shared location. It's recommended that the directory structure contained in the zip is not altered and games are built using that starting directory structure.

Public Repos link

Option 1 (Recommended) link

Your public repository needs only to contain the contents of ./mygame. This approach is the cleanest and doesn't require your .gitignore to be polluted with DragonRuby specific files.

Option 2 (Restrictions Apply) link

NOTE:

Do NOT commit dragonruby-publish(.exe), or dragonruby-bind(.exe).

dragonruby
dragonruby.exe
dragonruby-publish
dragonruby-publish.exe
dragonruby-bind
dragonruby-bind.exe
/tmp/
/builds/
/logs/
/samples/
/docs/
/.dragonruby/

If you'd like people who do not own a DragonRuby license to run your game, you may include the dragonruby(.exe) binary within the repo. This permission is granted in good-faith and can be revoked if abused.

Private Repos / Commercial Games link

The following .gitignore should be used for private repositories (commercial games).

/tmp/
/logs/

You'll notice that everything else is committed to source control (even the ./samples, ./docs, and ./builds directory).

NOTE:

The DragonRuby binary/package is designed to be committed in its entirety with your source code (it’s why we keep it small). This protects the “shelf life” for commercial games. 3 years from now, we might be on a vastly different version of the engine. But you know that the code you’ve written will definitely work with the version that was committed to source control.

Deploying To Itch.io link

Once you've built your game, you're all set to deploy! Good luck in your game dev journey and if you get stuck, come to the Discord channel!

Creating Your Game Landing Page link

Log into Itch.io and go to <https://itch.io/game/new>.

Title: Give your game a Title. This value represents your \gametitle\.
Project URL: Set your project url. This value represents your \gameid\.
Classification: Keep this as Game.
Kind of Project: Select HTML from the drop down list. Don't worry, the HTML project type <span class="underline">also supports binary downloads</span>.
Uploads: Skip this section for now.

You can fill out all the other options later.

Update Your Game's Metadata link

Point your text editor at mygame/metadata/game_metadata.txt and make it look like this:

NOTE: Remove the # at the beginning of each line.

devid=bob
devtitle=Bob The Game Developer
gameid=mygame
gametitle=My Game
version=0.1

The devid property is the username you use to log into Itch.io. The devtitle is your name or company name (it can contain spaces). The gameid is the Project URL value. The gametitle is the name of your game (it can contain spaces). The version can be any major.minor number format.

Building Your Game For Distribution link

Open up the terminal and run this from the command line:

./dragonruby-publish --package mygame

NOTE:

If you're on Windows, don't put the "./" on the front. That's a Mac and Linux thing.

A directory called ./build will be created that contains your binaries. You can upload this to Itch.io manually.

Browser Game Settings link

For the HTML version of your game, the following configuration is required for your game to run correctly:

Check the checkbox labeled This file will be played in the browser for the html version of your game (it's one of the zip files you'll upload).
Ensure that Embed options -> SharedArrayBuffer support is checked.
Be sure to set the Viewport dimensions to 1280x720 for landscape games or your game will not be positioned correctly on your Itch.io page.
Be sure to set the Viewport dimensions to 540x960 for portrait games or your game will not be positioned correctly on your Itch.io page.

For subsequent updates you can use an automated deployment to Itch.io:

./dragonruby-publish mygame

DragonRuby will package <span class="underline">and publish</span> your game to itch.io! Tell your friends to go to your game's very own webpage and buy it!

If you make changes to your game, just re-run dragonruby-publish and it'll update the downloads for you.

Consider Adding Pause When Game is In Background link

It's a good idea to pause the game if it doesn't have focus. Here's an example of how to do that

def tick args
  # if the keyboard doesn't have focus, and the game is in production mode, and it isn't the first tick
  if (!args.inputs.keyboard.has_focus &&
      args.gtk.production &&
      Kernel.tick_count != 0)
    args.outputs.background_color = [0, 0, 0]
    args.outputs.labels << { x: 640,
                             y: 360,
                             text: "Game Paused (click to resume).",
                             alignment_enum: 1,
                             r: 255, g: 255, b: 255 }
    # consider setting all audio volume to 0.0
  else
    # perform your regular tick function
  end
end

If you want your game to run at full speed even when it's in the background, add the following line to mygame/metadata/cvars.txt:

renderer.background_sleep=0

Consider Adding a Request to Review Your Game In-Game link

Getting reviews of your game are extremely important and it's recommended that you put an option to review within the game itself. You can use args.gtk.open_url plus a review URL. Here's an example:

def tick args
  # render the review button
  args.state.review_button ||= { x:    640 - 50,
                                 y:    360 - 25,
                                 w:    100,
                                 h:    50,
                                 path: :pixel,
                                 r:    0,
                                 g:    0,
                                 b:    0 }
  args.outputs.sprites << args.state.review_button
  args.outputs.labels << { x: 640,
                           y: 360,
                           anchor_x: 0.5,
                           anchor_y: 0.5,
                           text: "Review" }

  # check to see if the review button was clicked
  if args.inputs.mouse.intersect_rect? args.state.review_button
    # open platform specific review urls
    if args.gtk.platform? :ios
      # your app id is provided at Apple's Developer Portal (numeric value)
      args.gtk.openurl "itms-apps://itunes.apple.com/app/idYOURGAMEID?action=write-review"
    elsif args.gtk.platform? :android
      # your app id is the name of your android package
      args.gtk.openurl "https://play.google.com/store/apps/details?id=YOURGAMEID"
    elsif args.gtk.platform? :web
      # if they are playing the web version of the game, take them to the purchase page on itch
      args.gtk.openurl "https://amirrajan.itch.io/YOURGAMEID/purchase"
    else
      # if they are playing the desktop version of the game, take them to itch's rating page
      args.gtk.openurl "https://amirrajan.itch.io/YOURGAMEID/rate?source=game"
    end
  end
end

Deploying To Mobile Devices link

If you have a Pro subscription, you also have the capability to deploy to mobile devices.

Deploying to iOS link

To deploy to iOS, you need to have a Mac running MacOS Catalina, an iOS device, and an active/paid Developer Account with Apple. From the Console type: $wizards.ios.start and you will be guided through the deployment process.

$wizards.ios.start env: :dev will deploy to an iOS device connected via USB.
$wizards.ios.start env: :hotload will deploy to an iOS device connected via USB with hotload enabled.
$wizards.ios.start env: :sim will deploy to the iOS simulator.
$wizards.ios.start env: :prod will package your game for distribution via Apple's AppStore.

Deploying to Android link

To deploy to Android, you need to have an Android emulator/device, and an environment that is able to run Android SDK. dragonruby-publish will create an APK for you. From there, you can sign the APK and install it to your device. The signing and installation procedure varies from OS to OS. Here's an example of what the command might look like:

NOTE:

Be sure you specify packageid=TLD.YOURCOMPANY.YOURGAME (reverse domain name convention) within metadata/game_metadata.txt before running dragonruby-publish (for example: packageid=com.tempuri.mygame).

# generating a keystore (one time creation, save key to ./profiles for safe keeping)
keytool -genkey -v -keystore APP.keystore -alias mygame -keyalg RSA -keysize 2048 -validity 10000

# signing binaries
apksigner sign --min-sdk-version 26 --ks ./profiles/APP.keystore ./builds/APP-android.apk
apksigner sign --min-sdk-version 26 --ks ./profiles/APP.keystore ./builds/APP-googleplay.aab

# Deploying APK to a local device/emulator
adb install ./builds/APP-android.apk

# Deploying Google Play APK to a local device/emulator
bundletool build-apks --bundle=./builds/APP-googleplay.aab --output=./builds/app.apks --mode=universal
mv ./builds/app.apks ./builds/app.zip
cd ./builds
rm -rf tmp
mkdir tmp
cd tmp
unzip ../app.zip
cp ./universal.apk ./universal.zip
unzip ./universal.zip

# uninstall, install, launch
adb shell am force-stop PACKAGEID
adb uninstall PACKAGEID
adb install ./universal.apk
adb shell am start -n PACKAGEID/PACKAGEID.DragonRubyActivity

# read logs of device
adb logcat -e mygame

DragonRuby's Philosophy link

The following tenants of DragonRuby are what set us apart from other game engines. Given that Game Toolkit is a relatively new engine, there are definitely features that are missing. So having a big check list of "all the cool things" is not this engine's forte. This is compensated with a strong commitment to the following principles.

Challenge The Status Quo link

Game engines of today are in a local maximum and don't take into consideration the challenges of this day and age. Unity and GameMaker specifically rot your brain. It's not sufficient to say:

But that's how we've always done it.

It's a hard pill to swallow, but forget blindly accepted best practices and try to figure out the underlying motivation for a specific approach to game development. Collaborate with us.

Continuity of Design link

There is a programming idiom in software called "The Pit of Success". The term normalizes upfront pain as a necessity/requirement in the hopes that the investment will yield dividends "when you become successful" or "when the code becomes more complicated". This approach to development is strongly discouraged by us. It leads to over-architected and unnecessary code; creates barriers to rapid prototyping and shipping a game; and overwhelms beginners who are new to the engine or programming in general.

DragonRuby's philosophy is to provide multiple options across the "make it fast" vs "make it right" spectrum, with incremental/intuitive transitions between the options provided. A concrete example of this philosophy would be render primitives: the spectrum of options allows renderable constructs that take the form of tuples/arrays (easy to pickup, simple, and fast to code/prototype with), hashes (a little more work, but gives you the ability to add additional properties), open and strict entities (more work than hashes, but yields cleaner apis), and finally - if you really need full power/flexibility in rendering - classes (which take the most amount of code and programming knowledge to create).

Release Early and Often link

The biggest mistake game devs make is spending too much time in isolation building their game. Release something, however small, and release it soon.

Stop worrying about everything being pixel perfect. Don't wait until your game is 100% complete. Build your game publicly and iterate. Post in the #show-and-tell channel in the community Discord. You'll find a lot of support and encouragement there.

Real artists ship. Remember that.

Sustainable And Ethical Monetization link

We all aspire to put food on the table doing what we love. Whether it is building games, writing tools to support game development, or anything in between.

Charge a fair amount of money for the things you create. It's expected and encouraged within the community. Give what you create away for free to those that can't afford it.

If you are gainfully employed, pay full price for the things you use. If you do end up getting something at a discount, pay the difference "forward" to someone else.

Sustainable And Ethical Open Source link

This goes hand in hand with sustainable and ethical monetization. The current state of open source is not sustainable. There is an immense amount of contributor burnout. Users of open source expect everything to be free, and few give back. This is a problem we want to fix (we're still trying to figure out the best solution).

So, don't be "that guy" in the Discord that says "DragonRuby should be free and open source!" You will be personally flogged by Amir.

People Over Entities link

We prioritize the endorsement of real people over faceless entities. This game engine, and other products we create, are not insignificant line items of a large company. And you aren't a generic "commodity" or "corporate resource". So be active in the community Discord and you'll reap the benefits as more devs use DragonRuby.

Building A Game Should Be Fun And Bring Happiness link

We will prioritize the removal of pain. The aesthetics of Ruby make it such a joy to work with, and we want to capture that within the engine.

Real World Application Drives Features link

We are bombarded by marketing speak day in and day out. We don't do that here. There are things that are really great in the engine, and things that need a lot of work. Collaborate with us so we can help you reach your goals. Ask for features you actually need as opposed to anything speculative.

We want DragonRuby to -actually- help you build the game you want to build (as opposed to sell you something piece of demoware that doesn't work).

Frequently Asked Questions, Comments, and Concerns link

Here are questions, comments, and concerns that frequently come up.

Frequently Asked Questions link

What is DragonRuby LLP? link

DragonRuby LLP is a partnership of four devs who came together with the goal of bringing the aesthetics and joy of Ruby, everywhere possible.

Under DragonRuby LLP, we offer a number of products (with more on the way):

Game Toolkit (GTK): A 2D game engine that is compatible with modern gaming platforms.
RubyMotion (RM): A compiler toolchain that allows you to build native, cross-platform mobile apps. [http://rubymotion.com](http://rubymotion.com)

All of the products above leverage a shared core called DragonRuby.

NOTE:

NOTE: From an official branding standpoint each one of the products is suffixed with "A DragonRuby LLP Product" tagline. Also, DragonRuby is _one word, title cased_.

NOTE:

NOTE: We leave the "A DragonRuby LLP Product" off of this one because that just sounds really weird.

NOTE:

NOTE: Devs who use DragonRuby are "Dragon Riders/Riders of Dragons". That's a bad ass identifier huh?

What is DragonRuby? link

The response to this question requires a few subparts. First we need to clarify some terms. Specifically _language specification_ vs _runtime_.

--Okay... so what is the difference between a language specification and a runtime?--

A runtime is an _implementation_ of a language specification. When people say "Ruby," they are usually referring to "the Ruby 3.0+ language specification implemented via the CRuby/MRI Runtime."

But, there are many Ruby Runtimes: CRuby/MRI, JRuby, Truffle, Rubinius, Artichoke, and (last but certainly not least) DragonRuby.

--Okay... what language specification does DragonRuby use then?--

DragonRuby's goal is to be compliant with the ISO/IEC 30170:2012 standard. It's syntax is Ruby 2.x compatible, but also contains semantic changes that help it natively interface with platform specific libraries.

--So... why another runtime?--

The elevator pitch is:

DragonRuby is a Multilevel Cross-platform Runtime. The "multiple levels" within the runtime allows us to target platforms no other Ruby can target: PC, Mac, Linux, Raspberry Pi, WASM, iOS, Android, Nintendo Switch, PS4, Xbox, and Stadia.

What does Multilevel Cross-platform mean? link

There are complexities associated with targeting all the platforms we support. Because of this, the runtime had to be architected in such a way that new platforms could be easily added (which lead to us partitioning the runtime internally):

Level 1 we leverage a good portion of mRuby.
Level 2 consists of optimizations to mRuby we've made given that our target platforms are well known.
Level 3 consists of portable C libraries and their Ruby C-Extensions.

Levels 1 through 3 are fairly commonplace in many runtime implementations (with level 1 being the most portable, and level 3 being the fastest). But the DragonRuby Runtime has taken things a bit further:

Level 4 consists of shared abstractions around hardware I/O and operating system resources. This level leverages open source and proprietary components within Simple DirectMedia Layer (a low level multimedia component library that has been in active development for 22 years and counting).
Level 5 is a code generation layer which creates metadata that allows for native interoperability with host runtime libraries. It also includes OS specific message pump orchestrations.
Level 6 is a Ahead of Time/Just in Time Ruby compiler built with LLVM. This compiler outputs _very_ fast platform specific bitcode, but only supports a subset of the Ruby language specification.

These levels allow us to stay up to date with open source implementations of Ruby; provide fast, native code execution on proprietary platforms; ensure good separation between these two worlds; and provides a means to add new platforms without going insane.

--Cool cool. So given that I understand everything to this point, can we answer the original question? What is DragonRuby?--

DragonRuby is a Ruby runtime implementation that takes all the lessons we've learned from MRI/CRuby, and merges it with the latest and greatest compiler and OSS technologies.

How is DragonRuby different than MRI? link

DragonRuby supports a subset of MRI apis. Our target is to support all of mRuby's standard lib. There are challenges to this given the number of platforms we are trying to support (specifically console).

Does DragonRuby support Gems? link

DragonRuby does not support gems because that requires the installation of MRI Ruby on the developer's machine (which is a non-starter given that we want DragonRuby to be a zero dependency runtime). While this seems easy for Mac and Linux, it is much harder on Windows and Raspberry Pi. mRuby has taken the approach of having a git repository for compatible gems and we will most likely follow suite: https://github.com/mruby/mgem-list.

Does DragonRuby have a REPL/IRB? link

You can use DragonRuby's Console within the game to inspect object and execute small pieces of code. For more complex pieces of code create a file called repl.rb and put it in mygame/app/repl.rb:

Any code you write in there will be executed when you change the file. You can organize different pieces of code using the repl method:

repl do
  puts "hello world"
  puts 1 + 1
end

If you use the repl method, the code will be executed and the DragonRuby Console will automatically open so you can see the results (on Mac and Linux, the results will also be printed to the terminal). All puts statements will also be saved to logs/puts.txt. So if you want to stay in your editor and not look at the terminal, or the DragonRuby Console, you can tail this file. 4. To ignore code in repl.rb, instead of commenting it out, prefix repl with the letter x and it'll be ignored.

xrepl do # <------- line is prefixed with an "x"
  puts "hello world"
  puts 1 + 1
end

# This code will be executed when you save the file.
repl do
  puts "Hello"
end

repl do
  puts "This code will also be executed."
end

# use xrepl to "comment out" code
xrepl do
  puts "This code will not be executed because of the x in front of repl".
end

Does DragonRuby support pry or have any other debugging facilities? link

pry is a gem that assumes you are using the MRI Runtime (which is incompatible with DragonRuby). Eventually DragonRuby will have a pry based experience that is compatible with a debugging infrastructure called LLDB. Take the time to read about LLDB as it shows the challenges in creating something that is compatible.

You can use DragonRuby's replay capabilities to troubleshoot:

DragonRuby is hot loaded which gives you a very fast feedback loop (if the game throws an exception, it's because of the code you just added). Use ./dragonruby mygame --record to create a game play recording that you can use to find the exception (you can replay a recording by executing ./dragonruby mygame --replay last_replay.txt or through the DragonRuby Console using $gtk.recording.start_replay "last_replay.txt".

DragonRuby also ships with a unit testing facility. You can invoke the following command to run a test: ./dragonruby mygame --test tests/some_ruby_file.rb. Get into the habit of adding debugging facilities within the game itself. You can add drawing primitives to args.outputs.debug that will render on top of your game but will be ignored in a production release.

Debugging something that runs at 60fps is (imo) not that helpful. The exception you are seeing could have been because of a change that occurred many frames ago.

Frequent Comments About Ruby as a Language Choice link

But Ruby is dead. link

Let's check the official source for the answer to this question: [isrubydead.com](https://isrubydead.com/).

On a more serious note, Ruby's _quantity_ levels aren't what they used to be. And that's totally fine. Everyone chases the new and shiny.

What really matters is _quality/maturity_. Here's a StackOverflow Survey sorted by highest paid developers: https://insights.stackoverflow.com/survey/2021#section-top-paying-technologies-top-paying-technologies.

Let's stop making this comment shall we?

But Ruby is slow. link

That doesn't make any sense. A language specification can't be slow... it's a language spec. Sure, an _implementation/runtime_ can be slow though, but then we'd have to talk about which runtime.

Here are some quick demonstrations of how well DragonRuby Game Toolkit Performs:

DragonRuby vs Unity: https://youtu.be/MFR-dvsllA4
DragonRuby vs PyGame: https://youtu.be/fuRGs6j6fPQ

Dynamic languages are slow. link

They are certainly slower than statically compiled languages. With the processing power and compiler optimizations we have today, dynamic languages like Ruby are _fast enough_.

Unless you are writing in some form of intermediate representation by hand, your language of choice also suffers this same fallacy of slow. Like, nothing is faster than a low level assembly-like language. So unless you're writing in that, let's stop making this comment.

NOTE:

NOTE: If you _are_ hand writing LLVM IR, we are always open to bringing on new partners with such a skill set. Email us ^_^.

Frequent Concerns link

DragonRuby is not open source. That's not right. link

The current state of open source is unsustainable. Contributors work for free, most all open source repositories are severely under-staffed, and burnout from core members is rampant.

We believe in open source very strongly. Parts of DragonRuby are in fact, open source. Just not all of it (for legal reasons, and because the IP we've created has value). And we promise that we are looking for (or creating) ways to _sustainably_ open source everything we do.

If you have ideas on how we can do this, email us!

If the reason above isn't sufficient, then definitely use something else.

All this being said, we do have parts of the engine open sourced on GitHub: https://github.com/dragonruby/dragonruby-game-toolkit-contrib/

DragonRuby is for pay. You should offer a free version. link

If you can afford to pay for DragonRuby, you should (and will). We don't tell authors that they should give us their books for free, and only require payment if we read the entire thing. It's time we stop asking that of software products.

That being said, we will _never_ put someone out financially. We have income assistance for anyone that can't afford a license to any one of our products.

You qualify for a free, unrestricted license to DragonRuby products if any of the following items pertain to you:

Your income is below $2,000.00 (USD) per month.
You are under 18 years of age.
You are a student of any type: traditional public school, home schooling, college, bootcamp, or online.
You are a teacher, mentor, or parent who wants to teach a kid how to code.
You work/worked in public service or at a charitable organization: for example public office, army, or any 501(c)(3) organization.

Just contact Amir at [email protected] with a short explanation of your current situation and he'll set you up. No questions asked.

--But still, you should offer a free version. So I can try it out and see if I like it.--

You can try our web-based sandbox environment at http://fiddle.dragonruby.org. But it won't do the runtime justice. Or just come to our Discord Channel at http://discord.dragonruby.org and ask questions. We'd be happy to have a one on one video chat with you and show off all the cool stuff we're doing.

Seriously just buy it. Get a refund if you don't like it. We make it stupid easy to do so.

--I still think you should do a free version. Think of all people who would give it a shot.--

Free isn't a sustainable financial model. We don't want to spam your email. We don't want to collect usage data off of you either. We just want to provide quality toolchains to quality developers (as opposed to a large quantity of developers).

The people that pay for DragonRuby and make an effort to understand it are the ones we want to build a community around, partner with, and collaborate with. So having that small monetary wall deters entitled individuals that don't value the same things we do.

What if I build something with DragonRuby, but DragonRuby LLP becomes insolvent. link

We want to be able to work on the stuff we love, every day of our lives. And we'll go to great lengths to make that continues.

But, in the event that sad day comes, our partnership bylaws state that _all_ DragonRuby IP that can be legally open sourced, will be released under a permissive license.

Troubleshoot Performance link

Avoid deep recursive calls.
If you're using Arrays for your primitives (args.outputs.sprites << []), use Hash instead (args.outputs.sprites << { x: ... }).
If you're using Entity for your primitives (args.outputs.sprites << args.state.new_entity), use StrictEntity instead (args.outputs.sprites << args.state.new_entity_strict).
Use .each instead of .map if you don't care about the return value.
When concatenating primitives to outputs, do them in bulk. Instead of:

args.state.bullets.each do |bullet|
  args.outputs.sprites << bullet.sprite
end

args.outputs.sprites << args.state.bullets.map do |b|
  b.sprite
end

Use args.outputs.static_ variant for things that don't change often (take a look at the Basic Gorillas sample app and Dueling Starships sample app to see how static_ is leveraged.
Consider using a render_target if you're doing some form of a camera that moves a lot of primitives (take a look at the Render Target sample apps for more info).
Avoid deleting or adding to an array during iteration. Instead of:

args.state.fx_queue.each |fx|
  fx.count_down ||= 255
  fx.countdown -= 5
  if fx.countdown < 0
    args.state.fx_queue.delete fx
  end
end

Do:

args.state.fx_queue.each |fx|
  fx.countdown ||= 255
  fx.countdown -= 5
end

args.state.fx_queue.reject! { |fx| fx.countdown < 0 }

Using `args.state` To Store Your Game State link

args.state is a open data structure that allows you to define properties that are arbitrarily nested. You don't need to define any kind of class.

To initialize your game state, use the ||= operator. Any value on the right side of ||= will only be assigned _once_.

To assign a value every frame, just use the = operator, but _make sure_ you've initialized a default value.

def tick args
  # initialize your game state ONCE
  args.state.player.x  ||= 0
  args.state.player.y  ||= 0
  args.state.player.hp ||= 100

  # increment the x position of the character by one every frame
  args.state.player.x += 1

  # Render a sprite with a label above the sprite
  args.outputs.sprites << [
    args.state.player.x,
    args.state.player.y,
    32, 32,
    "player.png"
  ]

  args.outputs.labels << [
    args.state.player.x,
    args.state.player.y - 50,
    args.state.player.hp
  ]
end

Accessing files link

DragonRuby uses a sandboxed filesystem which will automatically read from and write to a location appropriate for your platform so you don't have to worry about theses details in your code. You can just use gtk.read_file, gtk.write_file, and gtk.append_file with a relative path and the engine will take care of the rest.

The data directories that will be written to in a production build are:

Windows: C:\Users\[username]\AppData\Roaming\[devtitle]\[gametitle]
MacOS: $HOME/Library/Application Support/[gametitle]
Linux: $HOME/.local/share/[gametitle]
HTML5: The data will be written to the browser's IndexedDB.

The values in square brackets are the values you set in your app/metadata/game_metadata.txt file.

When reading files, the engine will first look in the game's data directory and then in the game directory itself. This means that if you write a file to the data directory that already exists in your game directory, the file in the data directory will be used instead of the one that is in your game.

When running a development build you will directly write to your game directory (and thus overwrite existing files). This can be useful for built-in development tools like level editors.

For more details on the implementation of the sandboxed filesystem, see Ryan C. Gordon's PhysicsFS documentation: https://icculus.org/physfs/

IMPORTANT: File access functions are sandoxed and assume that the dragonruby binary lives alongside the game you are building. Do not expect file access functions to return correct values if you are attempting to run the dragonruby binary from a shared location. It's recommended that the directory structure contained in the zip is not altered and games are built using that starter template.

How To Render A Sprite Using An Array link

All file paths should use the forward slash / *not* backslash \. Game Toolkit includes a number of sprites in the sprites folder (everything about your game is located in the mygame directory).

The following code renders a sprite with a width and height of 100 in the center of the screen.

args.outputs.sprites is used to render a sprite.

NOTE: Rendering using an Array is "quick and dirty". It's generally recommended that you render using Hashes long term.

def tick args
  args.outputs.sprites << [
    640 - 50,                 # X
    360 - 50,                 # Y
    100,                      # W
    100,                      # H
    'sprites/square-blue.png' # PATH
 ]
end

Rendering a Sprite Using a `Hash` link

Using ordinal positioning can get a little unruly given so many properties you have control over.

You can represent a sprite as a Hash:

def tick args
  args.outputs.sprites << {
    x: 640 - 50,
    y: 360 - 50,
    w: 100,
    h: 100,

    path: 'sprites/square-blue.png',
    angle: 0,

    a: 255,
    r: 255,
    g: 255,
    b: 255,

    # source_ properties have origin of bottom left
    source_x:  0,
    source_y:  0,
    source_w: -1,
    source_h: -1,

    # tile_ properties have origin of top left
    tile_x:  0,
    tile_y:  0,
    tile_w: -1,
    tile_h: -1,

    flip_vertically: false,
    flip_horizontally: false,

    angle_anchor_x: 0.5,
    angle_anchor_y: 1.0,

    blendmode_enum: 1

    # sprites anchor/alignment (default is nil)
    anchor_x: 0.5,
    anchor_y: 0.5
  }
end

The blendmode_enum value can be set to 0 (no blending), 1 (alpha blending), 2 (additive blending), 3 (modulo blending), 4 (multiply blending).

RECIPIES: link

How To Determine What Frame You Are On link

There is a property on state called tick_count that is incremented by DragonRuby every time the tick method is called. The following code renders a label that displays the current tick_count.

def tick args
  args.outputs.labels << [10, 670, "\#{Kernel.tick_count}"]
end

How To Get Current Framerate link

Current framerate is a top level property on the Game Toolkit Runtime and is accessible via args.gtk.current_framerate.

def tick args
  args.outputs.labels << [10, 710, "framerate: \#{args.gtk.current_framerate.round}"]
end

How To Play A Sound link

Sounds that end .wav will play once:

def tick args
  # Play a sound every second
  if (Kernel.tick_count % 60) == 0
    args.outputs.sounds << 'something.wav'
  end
end

Sounds that end .ogg is considered background music and will loop:

def tick args
  # Start a sound loop at the beginning of the game
  if Kernel.tick_count == 0
    args.outputs.sounds << 'background_music.ogg'
  end
end

If you want to play a .ogg once as if it were a sound effect, you can do:

def tick args
  # Play a sound every second
  if (Kernel.tick_count % 60) == 0
    args.gtk.queue_sound 'some-ogg.ogg'
  end
end

How To Render A Label link

args.outputs.labels is used to render labels.

Labels are how you display text. This code will go directly inside of the def tick args method.

NOTE: Rendering using an Array is "quick and dirty". It's generally recommended that you render using Hashes long term.

Here is the minimum code:

def tick args
  #                       X    Y    TEXT
  args.outputs.labels << [640, 360, "I am a black label."]
end

A Colored Label link

def tick args
  # A colored label
  #                       X    Y    TEXT,                   RED    GREEN  BLUE  ALPHA
  args.outputs.labels << [640, 360, "I am a redish label.", 255,     128,  128,   255]
end

Extended Label Properties link

def tick args
  # A colored label
  #                       X    Y     TEXT           SIZE  ALIGNMENT  RED  GREEN  BLUE  ALPHA  FONT FILE
  args.outputs.labels << [
    640,                   # X
    360,                   # Y
    "Hello world",         # TEXT
    0,                     # SIZE_ENUM
    1,                     # ALIGNMENT_ENUM
    0,                     # RED
    0,                     # GREEN
    0,                     # BLUE
    255,                   # ALPHA
    "fonts/coolfont.ttf"   # FONT
  ]
end

A SIZE_ENUM of 0 represents "default size". A negative value will decrease the label size. A positive value will increase the label's size.

An ALIGNMENT_ENUM of 0 represents "left aligned". 1 represents "center aligned". 2 represents "right aligned".

Rendering A Label As A `Hash` link

You can add additional metadata about your game within a label, which requires you to use a `Hash` instead.

If you use a Hash to render a label, you can set the label's size using either SIZE_ENUM or SIZE_PX. If both options are provided, SIZE_PX will be used.

def tick args
  args.outputs.labels << {
    x:                       200,
    y:                       550,
    text:                    "dragonruby",
    # size specification can be either size_enum or size_px
    size_enum:               2,
    size_px:                 22,
    alignment_enum:          1,
    r:                       155,
    g:                       50,
    b:                       50,
    a:                       255,
    font:                    "fonts/manaspc.ttf",
    vertical_alignment_enum: 0, # 0 is bottom, 1 is middle, 2 is top
    anchor_x: 0.5,
    anchor_y: 0.5
    # You can add any properties you like (this will be ignored/won't cause errors)
    game_data_one:  "Something",
    game_data_two: {
       value_1: "value",
       value_2: "value two",
       a_number: 15
    }
  }
end

Getting The Size Of A Piece Of Text link

You can get the render size of any string using args.gtk.calcstringbox.

def tick args
  #                             TEXT           SIZE_ENUM  FONT
  w, h = args.gtk.calcstringbox("some string",         0, "font.ttf")

  # NOTE: The SIZE_ENUM and FONT are optional arguments.

  # Render a label showing the w and h of the text:
  args.outputs.labels << [
    10,
    710,
    # This string uses Ruby's string interpolation literal: #{}
    "'some string' has width: #{w}, and height: #{h}."
  ]
end

Rendering Labels With New Line Characters And Wrapping link

You can use a strategy like the following to create multiple labels from a String.

def tick args
  long_string = "Lorem ipsum dolor sit amet, consectetur adipiscing elitteger dolor velit, ultricies vitae libero vel, aliquam imperdiet enim."
  max_character_length = 30
  long_strings_split = args.string.wrapped_lines long_string, max_character_length
  args.outputs.labels << long_strings_split.map_with_index do |s, i|
    { x: 10, y: 600 - (i * 20), text: s }
  end
end

Outputs (`args.outputs`) link

Outputs is how you render primitives to the screen. The minimal setup for rendering something to the screen is via a tick method defined in mygame/app/main.rb

def tick args
  args.outputs.solids     << { x: 0, y: 0, w: 100, h: 100 }
  args.outputs.sprites    << { x: 100, y: 100, w: 100, h: 100, path: "sprites/square/blue.png" }
  args.outputs.labels     << { x: 200, y: 200, text: "Hello World" }
  args.outputs.borders    << { x: 0, y: 0, w: 100, h: 100 }
  args.outputs.lines      << { x: 300, y: 300, x2: 400, y2: 400 }
end

Collection Render Orders link

Primitives are rendered first-in, first-out. The rendering order (sorted by bottom-most to top-most):

solids
sprites
primitives: Accepts all render primitives. Useful when you want to bypass the default rendering orders for rendering (eg. rendering solids on top of sprites).
labels
lines
borders
debug: Accepts all render primitives. Use this to render primitives for debugging (production builds of your game will not render this layer).

`primitives` link

args.outputs.primitives can take in any primitive and will render first in, first out.

For example, you can render a solid above a sprite:

def tick args
  # sprite
  args.outputs.primitives << { x: 100, y: 100,
                               w: 100, h: 100,
                               path: "sprites/square/blue.png" }

  # solid
  args.outputs.primitives << { x: 0,
                               y: 0,
                               w: 100,
                               h: 100,
                               primitive_marker: :solid }

  # border
  args.outputs.primitives << { x: 0,
                               y: 0,
                               w: 100,
                               h: 100,
                               primitive_marker: :border }

  # label
  args.outputs.primitives << { x: 100, y: 100,
                               text: "hello world" }

  # line
  args.outputs.primitives << { x: 100, y: 100, x2: 150, y2: 150 }
end

`debug` link

args.outputs.debug will not render in production mode and behaves like args.outputs.primitives. Objects in this collection are rendered above everything.

String Primitives link

Additionally, args.outputs.debug allows you to pass in a String as a primitive type. This is helpful for quickly showing the value of a variable on the screen. A label with black text and a white background will be created for each String sent in. The labels will be automatically stacked vertically for you. New lines in the string will be respected.

Example:

def tick args
  args.state.player ||= { x: 100, y: 100 }
  args.state.player.x += 1
  args.state.player.x = 0 if args.state.player.x > 1280

  # the following string values will generate labels with backgrounds
  # and will auto stack vertically
  args.outputs.debug << "current tick: #{Kernel.tick_count}"
  args.outputs.debug << "player x: #{args.state.player.x}"
  args.outputs.debug << "hello\nworld"
end

`watch` link

If you need additional control over a string value, you can use the args.outputs.debug.watch function.

The functions takes in the following parameters:

Object to watch. This object will be converted to a string.
The label_style: optional, named argument can be passed in with a Hash to override the default label style for watch variables.
The background_style: optional named argument can be passed in with a Hash to override the default background style for the watch variables.

Example:

def tick args
  args.state.player ||= { x: 100, y: 100 }
  args.state.player.x += 1
  args.state.player.x = 0 if args.state.player.x > 1280

  args.outputs.debug.watch args.state.player
  args.outputs.debug.watch pretty_format(args.state.player),
                           label_style: { r: 0,
                                          g: 0,
                                          b: 255,
                                          size_px: 10 },
                           background_style: { r: 0,
                                               g: 255,
                                               b: 0,
                                               a: 128,
                                               path: :solid }
end

`solids` link

Add primitives to this collection to render a solid to the screen.

NOTE:

This render primitive is fine to use sparingly. If you find yourself rendering a large number of solids, render sprites instead (the textures that solid primitives generate are not cached and do not perform as well as rendering sprites).

For example, the following solid and sprite are equivalent:

def tick args
  args.outputs.solids << {
    x: 0,
    y: 0,
    w: 100,
    h: 100,
    r: 255,
    g: 255,
    b: 255,
    a: 128
  }

  # is equivalent to

  args.outputs.sprites << {
    x: 0,
    y: 0,
    w: 100,
    h: 100,
    path: :solid,
    r: 255,
    g: 255,
    b: 255,
    a: 128
  }
end

Rendering a Solid using an Array link

Creates a solid black rectangle located at 100, 100. 160 pixels wide and 90 pixels tall.

def tick args
  #                         X    Y  WIDTH  HEIGHT
  args.outputs.solids << [100, 100,   160,     90]
end

NOTE:

Array-based primitives are find for debugging purposes/quick prototypes. But should not be used as the default rendering approach. Use Hash-based or Class-based primitives.

Rendering a Solid using an Array with colors and alpha link

The value for the color and alpha is a number between 0 and 255. The alpha property is optional and will be set to 255 if not specified.

Creates a green solid rectangle with an opacity of 50%.

def tick args
  #                         X    Y  WIDTH  HEIGHT  RED  GREEN  BLUE  ALPHA
  args.outputs.solids << [100, 100,   160,     90,   0,   255,    0,   128]
end

Rendering a Solid using a Hash link

If you want a more readable invocation. You can use the following hash to create a solid. Any parameters that are not specified will be given a default value. The keys of the hash can be provided in any order.

def tick args
  args.outputs.solids << {
    x:    0,
    y:    0,
    w:  100,
    h:  100,
    r:    0,
    g:  255,
    b:    0,
    a:  255,
    anchor_x: 0,
    anchor_y: 0,
    blendmode_enum: 1
  }
end

Rendering a Solid using a Class link

You can also create a class with solid properties and render it as a primitive. ALL properties must be on the class. --Additionally--, a method called primitive_marker must be defined on the class.

Here is an example:

# Create type with ALL solid properties AND primitive_marker
class Solid
  attr_accessor :x, :y, :w, :h, :r, :g, :b, :a, :anchor_x, :anchor_y, :blendmode_enum

  def primitive_marker
    :solid # or :border
  end
end

# Inherit from type
class Square < Solid
  # constructor
  def initialize x, y, size
    self.x = x
    self.y = y
    self.w = size
    self.h = size
  end
end

def tick args
  # render solid/border
  args.outputs.solids  << Square.new(10, 10, 32)
end

`borders` link

Add primitives to this collection to render an unfilled solid to the screen. Take a look at the documentation for Outputs#solids.

The only difference between the two primitives is where they are added.

Instead of using args.outputs.solids:

def tick args
  #                         X    Y  WIDTH  HEIGHT
  args.outputs.solids << [100, 100,   160,     90]
end

You have to use args.outputs.borders:

def tick args
  #                           X    Y  WIDTH  HEIGHT
  args.outputs.borders << [100, 100,   160,     90]
end

`sprites` link

Add primitives to this collection to render a sprite to the screen.

Properties link

Here are all the properties that you can set on a sprite. The only required ones are x, y, w, h, and path.

Required

x: X position of the sprite. Note: the bottom left corner of the sprite is used for positioning (this can be changed using anchor_x, and anchor_y).
y: Y position of the sprite. Note: The origin 0,0 is at the bottom left corner. Setting y to a higher value will move the sprite upwards.
w: The render width.
h: The render height.
path: The path of the sprite relative to the game folder.

Anchors and Rotations

flip_horizontally: This value can be either true or false and controls if the sprite will be flipped horizontally (default value is false).
flip_vertically: This value can be either true or false and controls if the sprite will be flipped vertically (default value is false).
anchor_x: Used to determine anchor point of the sprite's X position (relative to the render width).
anchor_y: Used to determine anchor point of the sprite's Y position (relative to the render height).
angle: Rotation of the sprite in degrees (default value is 0). Rotation occurs around the center of the sprite. The point of rotation can be changed using angle_anchor_x and angle_anchor_y.
angle_anchor_x: Controls the point of rotation for the sprite (relative to the render width).
angle_anchor_y: Controls the point of rotation for the sprite (relative to the render height).

Here's an example of rendering a 80x80 pixel sprite in the center of the screen:

def tick args
  args.outputs.sprites << {
    x: 640 - 40, # the logical center of the screen horizontally is 640, minus half the width of the sprite
    y: 360 - 40, # the logical center of the screen vertically is 360, minus half the height of the sprite
    w: 80,
    h: 80,
    path: "sprites/square/blue.png"
 }
end

Instead of computing the offset, you can use anchor_x, and anchor_y to center the sprite. The following is equivalent to the code above:

def tick args
  args.outputs.sprites << {
    x: 640,
    y: 360,
    w: 80,
    h: 80,
    path: "sprites/square/blue.png",
    anchor_x: 0.5, # position horizontally at 0.5 of the sprite's width
    anchor_y: 0.5  # position vertically at 0.5 of the sprite's height
 }
end

Cropping

tile_(x|y|w|h): Defines the crop area to use for a sprite. The origin for tile_ properties uses the TOP LEFT as its origin (useful for cropping tiles from a sprite sheet).
source_(x|y|w|h): Defines the crop area to use for a sprite. The origin for tile_ properties uses the BOTTOM LEFT as its origin.

See the sample apps under ./samples/03_rendering_sprites for examples of how to use this properties non-trivially.

Blending

a: Alpha/transparency of the sprite from 0 to 255 (default value is 255).
r: Level of red saturation for the sprite (default value is 255). Example: Setting the value to zero will remove all red coloration from the sprite.
g: Level of green saturation for the sprite (default value is 255).
b: Level of blue saturation for the sprite (default value is 255).
blendmode_enum: Valid options are 0: no blending, 1: default/alpha blending, 2: additive blending, 3: modulo blending, 4: multiply blending.
scale_quality_enum: Valid options are 0: nearest neighbor, 1: linear scaling, 2: anti-aliasing. If the value is nil then the scale_quality value that was set in mygame/game_metadata.txt will be used.

The following sample apps show how blendmode_enum can be leveraged to create coloring and lighting effects:

./samples/07_advanced_rendering/11_blend_modes
./samples/07_advanced_rendering/13_lighting

Triangles (Indie, Pro Feature)

Sprites can be rendered as triangles at the Indie and Pro License Tiers. To rendering using triangles, instead of providing a w, h property, provide x2, y2, x3, y3. This applies for positioning and cropping.

Here is an example:

def tick args
  args.outputs.sprites << {
    x: 0,
    y: 0,
    x2: 80,
    y2: 0,
    x3: 0,
    y3: 80,
    source_x: 0,
    source_y: 0,
    source_x2: 80,
    source_y2: 0,
    source_x3: 0,
    source_y3: 80,
    path: "sprites/square/blue.png"
  }
end

For more example of rendering using triangles see:

./samples/07_advanced_rendering/14_triangles
./samples/07_advanced_rendering/15_triangles_trapezoid
./samples/07_advanced_rendering/16_matrix_and_triangles_2d
./samples/07_advanced_rendering/16_matrix_and_triangles_3d
./samples/07_advanced_rendering/16_matrix_cubeworld

Rendering a Sprite using an Array link

Creates a sprite of a white circle located at 100, 100. 160 pixels wide and 90 pixels tall.

def tick args
  #                         X    Y   WIDTH   HEIGHT                      PATH
  args.outputs.sprites << [100, 100,   160,     90, "sprites/circle/white.png"]
end

NOTE:

Array-based sprites have limited access to sprite properties, but nice for quick prototyping. Use a Hash or Class to gain access to all properties, gain long term maintainability of code, and a boost in rendering performance.

Rendering a Sprite using a Hash link

If you want a more readable (and faster) invocation, you can use the following hash to create a sprite. Any parameters that are not specified will be given a default value. The keys of the hash can be provided in any order.

def tick args
  args.outputs.sprites << {
    x: 0,
    y: 0,
    w: 100,
    h: 100,
    path: "sprites/circle/white.png",
    angle: 0,
    a: 255
  }
end

Rendering a Sprite using a Class link

You can also create a class with solid/border properties and render it as a primitive. ALL properties must be on the class. --Additionally--, a method called primitive_marker must be defined on the class.

Here is an example:

# Create type with ALL sprite properties AND primitive_marker
class Sprite
  attr_accessor :x, :y, :w, :h, :path, :angle, :a, :r, :g, :b, :tile_x,
                :tile_y, :tile_w, :tile_h, :flip_horizontally,
                :flip_vertically, :angle_anchor_x, :angle_anchor_y, :id,
                :angle_x, :angle_y, :z,
                :source_x, :source_y, :source_w, :source_h, :blendmode_enum,
                :source_x2, :source_y2, :source_x3, :source_y3, :x2, :y2, :x3, :y3,
                :anchor_x, :anchor_y, :scale_quality_enum

  def primitive_marker
    :sprite
  end
end

# Inherit from type
class Circle < Sprite
  # constructor
  def initialize x, y, size, path
    self.x = x
    self.y = y
    self.w = size
    self.h = size
    self.path = path
  end

  def serialize
    {x:self.x, y:self.y, w:self.w, h:self.h, path:self.path}
  end

  def inspect
    serialize.to_s
  end

  def to_s
    serialize.to_s
  end
end

def tick args
  # render circle sprite
  args.outputs.sprites  << Circle.new(10, 10, 32,"sprites/circle/white.png")
end

`attr_sprite` link

The attr_sprite class macro adds all properties needed to render a sprite to a class. This removes the need to manually define all sprites properties that DragonRuby offers for rendering.

Instead of manually defining the properties, you can represent a sprite using the attr_sprite class macro:

class BlueSquare
  # invoke the helper function at the class level for
  # anything you want to represent as a sprite
  attr_sprite

  def initialize(x: 0, y: 0, w: 0, h: 0)
    @x = x
    @y = y
    @w = w
    @h = h
    @path = 'sprites/square-blue.png'
  end
end

def tick args
  args.outputs.sprites << BlueSquare.new(x: 640 - 50,
                                         y: 360 - 50,
                                         w: 50,
                                         h: 50)
end

`lines` link

Add primitives to this collection to render a line.

Rendering a Line using an Array link

def tick args
                         #  X    Y   X2   Y2
  args.outputs.lines << [100, 100, 150, 150]
end

NOTE:

Array-based primitives are find for debugging purposes/quick prototypes. But should not be used as the default rendering approach. Use Hash-based or Class-based primitives.

Rendering a Line using a Hash link

def tick args
  args.outputs.lines << {
    x:  100,
    y:  100,
    x2: 150,
    y2: 150,
    r:  0,
    g:  0,
    b:  0,
    a:  255,
    blendmode_enum: 1
  }
end

Rendering a Line using a Class link

# Create type with ALL line properties AND primitive_marker
class Line
  attr_accessor :x, :y, :x2, :y2, :r, :g, :b, :a, :blendmode_enum

  def primitive_marker
    :line
  end
end

# Inherit from type
class RedLine < Line
  # constructor
  def initialize x, y, x2, y2
    self.x = x
    self.y = y
    self.x2 = x2
    self.y2 = y2
    self.r  = 255
    self.g  = 0
    self.b  = 0
    self.a  = 255
  end
end

def tick args
  # render line
  args.outputs.lines << RedLine.new(100, 100, 150, 150)
end

`labels` link

Add primitives to this collection to render a label.

Rendering a Label using an Array link

Labels represented as Arrays/Tuples:

def tick args
                         #        X         Y              TEXT   SIZE_ENUM
  args.outputs.labels << [175 + 150, 610 - 50, "Smaller label.",         0]
end

Here are all the properties that you can set with a label represented as an Array. It's recommended to move over to using Hashes once you've specified a lot of properties.

def tick args
  args.outputs.labels << [
    640,                   # X
    360,                   # Y
    "Hello world",         # TEXT
    0,                     # SIZE_ENUM
    1,                     # ALIGNMENT_ENUM
    0,                     # RED
    0,                     # GREEN
    0,                     # BLUE
    255,                   # ALPHA
    "fonts/coolfont.ttf"   # FONT
  ]
end

NOTE:

Array-based primitives are find for debugging purposes/quick prototypes. But should not be used as the default rendering approach. Use Hash-based or Class-based primitives.

Rendering a Label using a Hash link

?> size_enum is an opaque unit and signifies the recommended size for labels. The default size_enum of 0 means "this size is the smallest font size that is comfortable to read on a hand-held device". size_enum of 0 corresponds to 22px at 720p. Each increment of size_enum increases/decreases the pixels by 2 (size_enum of 1 means 24px, size_enum of -1 means 20px, etc). If you want to control the size of a label explicitly, use size_px instead.

def tick args
  args.outputs.labels << {
      x:                       200,
      y:                       550,
      text:                    "dragonruby",
      size_enum:               2,
      alignment_enum:          1, # 0 = left, 1 = center, 2 = right
      r:                       155,
      g:                       50,
      b:                       50,
      a:                       255,
      font:                    "fonts/manaspc.ttf",
      vertical_alignment_enum: 0  # 0 = bottom, 1 = center, 2 = top,
      anchor_x:                0, # if provided, alignment_enum is ignored
      anchor_y:                1, # if provided, vertical_alignment_enum is ignored,
      size_px:                 30, # if provided, size_enum is ignored.
      blendmode_enum:          1
  }
end

Rendering a Label using a Class link

# Create type with ALL label properties AND primitive_marker
class Label
  attr_accessor :x, :y, :w, :h, :r, :g, :b, :text, :font, :anchor_x,
                :anchor_y, :blendmode_enum, :size_px, :size_enum, :alignment_enum,
                :vertical_alignment_enum

  def primitive_marker
    :solid # or :border
  end
end

`screenshots` link

Add a hash to this collection to take a screenshot and save as png file. The keys of the hash can be provided in any order.

def tick args
  args.outputs.screenshots << {
    x: 0, y: 0, w: 100, h: 100,    # Which portion of the screen should be captured
    path: 'screenshot.png',        # Output path of PNG file (inside game directory)
    r: 255, g: 255, b: 255, a: 0   # Optional chroma key
  }
end

Chroma key (Making a color transparent) link

By specifying the r, g, b and a keys of the hash you change the transparency of a color in the resulting PNG file. This can be useful if you want to create files with transparent background like spritesheets. The transparency of the color specified by r, g, b will be set to the transparency specified by a.

The example above sets the color white (255, 255, 255) as transparent.

Shaders link

Shaders are available to Indie and Pro license holders via dragonruby-shadersim. Download DragonRuby ShaderSim at [dragonruby.org](https://dragonruby.org).

NOTE:

Shaders are currently in Beta.

Shaders must be GLSL ES2 compatible.

The long term goal is for DR Shaders to baseline to GLSL version 300 and cross-compile to Vulkan, WebGL 2, Metal, and HLSL.

Here is a minimal example of using shaders:

# mygame/app/main.rb
def tick args
  args.outputs.shader_path ||= "shaders/example.glsl"
end

// mygame/shaders/example.glsl
uniform sampler2D tex0;

varying vec2 v_texCoord;

void main() {
  gl_FragColor = texture2D(tex0, v_texCoord);
}

`shader_path` link

Setting shader_path on outputs signifies to DragonRuby that a shader should be compiled and loaded.

`shader_uniforms` link

You can bind uniforms to a shader by providing an Array of Hashes to shader_uniforms with keys name:, value:, and type: which currently supports :int and :float.

def tick args
  args.outputs.shader_path ||= "shaders/example.glsl"

  args.outputs.shader_uniforms = [
    {
      name: :mouse_coord_x,
      value: args.inputs.mouse.x.fdiv(1280),
      type: :float
    },
    {
      name: :mouse_coord_y,
      value: 1.0 - args.inputs.mouse.y.fdiv(720),
      type: :float
    },
    {
      name: :tick_count,
      value: Kernel.tick_count,
      type: :int
    }
  ]
end

// mygame/shaders/example.glsl
uniform sampler2D tex0;

uniform float mouse_coord_x;
uniform float mouse_coord_y;
uniform int tick_count;

varying vec2 v_texCoord;

void main() {
  gl_FragColor = texture2D(tex0, v_texCoord);
}

`shader_tex(1-15)` link

You can bind up to 15 additional render targets via shaders_tex1, shaders_tex2, shaders_tex3, etc. tex0 is reserved for what has been rendered to the screen and cannot be set.

def tick args
  args.outputs.shader_path = "shaders/example.glsl"
  args.outputs.shader_tex1 = :single_blue_square

  args.outputs[:single_blue_square].background_color = { r: 255, g: 255, b: 255, a: 255 }
  args.outputs[:single_blue_square].w = 1280;
  args.outputs[:single_blue_square].h = 720;
  args.outputs[:single_blue_square].sprites << {
    x: 0,
    y: 0,
    w: 100,
    h: 100,
    path:
    "sprites/square/blue.png"
  }

  args.outputs.background_color = { r: 0, g: 0, b: 0 }
  args.outputs.sprites << {
    x: 0,
    y: 0,
    w: 200,
    h: 200,
    path:
    "sprites/square/red.png"
  }
end

uniform sampler2D tex0;
uniform sampler2D tex1; // :single_blue_square render target

varying vec2 v_texCoord;

void noop() {
  vec4 pixel_from_rt = texture2D(tex1, v_texCoord);

  // if the pixel from the render target isn't white
  // then render the pixel from the RT
  // otherwise render the pixel from the screen
  if (pixel_from_rt.r < 1.0 ||
      pixel_from_rt.g < 1.0 ||
      pixel_from_rt.b < 1.0) {
    gl_FragColor.r = pixel_from_rt.r;
    gl_FragColor.g = pixel_from_rt.g;
    gl_FragColor.b = pixel_from_rt.b;
  } else {
    gl_FragColor = texture2D(tex0, v_texCoord);
  }
}

Inputs (`args.inputs`) link

Access using input using args.inputs.

`last_active` link

This function returns the last active input which will be set to either :keyboard, :mouse, or :controller. The function is helpful when you need to present on screen instructions based on the input the player chose to play with.

def tick args
  if args.inputs.last_active == :controller
    args.outputs.labels << { x: 60, y: 60, text: "Use the D-Pad to move around." }
  else
    args.outputs.labels << { x: 60, y: 60, text: "Use the arrow keys to move around." }
  end
end

The function is helpful when you need to present on screen instructions based on the input the player chose to play with.

`last_active_at` link

Returns Kernel.tick_count of which the specific input was last active.

`last_active_global_at` link

Returns the Kernel.global_tick_count of which the specific input was last active.

`locale` link

Returns the ISO 639-1 two-letter language code based on OS preferences. Refer to the following link for locale strings: <https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes>).

Defaults to "en" if locale can't be retrieved (args.inputs.locale_raw will be nil in this case).

`up` link

Returns true if: the up arrow or w key is pressed or held on the keyboard; or if up is pressed or held on controller_one; or if the left_analog on controller_one is tilted upwards.

`down` link

Returns true if: the down arrow or s key is pressed or held on the keyboard; or if down is pressed or held on controller_one; or if the left_analog on controller_one is tilted downwards.

`left` link

Returns true if: the left arrow or a key is pressed or held on the keyboard; or if left is pressed or held on controller_one; or if the left_analog on controller_one is tilted to the left.

`right` link

Returns true if: the right arrow or d key is pressed or held on the keyboard; or if right is pressed or held on controller_one; or if the left_analog on controller_one is tilted to the right.

`left_right` link

Returns -1 (left), 0 (neutral), or +1 (right). This method is aliased to args.inputs.left_right_with_wasd.

The following inputs are inspected to determine the result:

Keyboard's left, right arrow keys: args.inputs.keyboard.(left|right)_arrow
Keyboard's a, d keys (WASD): args.inputs.keyboard.(a|d)
Controller One's DPAD (if a controller is connected): args.inputs.controller_one.dpad_left, args.inputs.controller_one.dpad_right
Controller One's Left Analog (if a controller is connected): args.inputs.controller_one.left_analog_x_perc.abs >= 0.6

`left_right_perc` link

Returns a floating point value between -1 and 1. This method is aliased to args.inputs.left_right_perc_with_wasd

The following inputs are inspected to determine the result:

Controller One's Left Analog (if a controller is connected and the value is not 0.0): args.inputs.controller_one.left_analog_x_perc
If the left analog isn't being used, then Controller One's DPAD is consulted: args.inputs.controller_one.dpad_left, args.inputs.controller_one.dpad_right
Keyboard's a, d keys (WASD): args.inputs.keyboard.(a|d)
Keyboard's left/right arrow keys: args.inputs.keyboard.(left|right)_arrow

`left_right_directional` link

Returns -1 (left), 0 (neutral), or +1 (right). This method is aliased to args.inputs.left_right_arrow.

The following inputs are inspected to determine the result:

Keyboard's left/right arrow keys: args.inputs.keyboard.(left|right)_arrow
Controller One's DPAD (if a controller is connected): args.inputs.controller_one.dpad_left, args.inputs.controller_one.dpad_right
WASD and Controller One's Left Analog Stick are NOT consulted.

`left_right_directional_perc` link

Returns a floating point value between -1 and 1. The following inputs are inspected to determine the result:

Controller One's Left Analog (if a controller is connected and the value is not 0.0): args.inputs.controller_one.left_analog_x_perc
If the left analog isn't being used, then Controller One's DPAD is consulted: args.inputs.controller_one.dpad_left, args.inputs.controller_one.dpad_right
Keyboard's left/right arrow keys: args.inputs.keyboard.(left|right)_arrow
WASD is NOT consulted.

Here is some sample code to help visualize the left_right functions.

def tick args
  args.outputs.debug << "* Variations of args.inputs.left_right"
  args.outputs.debug << "  args.inputs.left_right(_with_wasd) #{args.inputs.left_right}"
  args.outputs.debug << "  args.inputs.left_right_perc(_with_wasd) #{args.inputs.left_right_perc}"
  args.outputs.debug << "  args.inputs.left_right_directional #{args.inputs.left_right_directional}"
  args.outputs.debug << "  args.inputs.left_right_directional_perc #{args.inputs.left_right_directional_perc}"
  args.outputs.debug << "** Keyboard"
  args.outputs.debug << "   args.inputs.keyboard.a #{args.inputs.keyboard.a}"
  args.outputs.debug << "   args.inputs.keyboard.d #{args.inputs.keyboard.d}"
  args.outputs.debug << "   args.inputs.keyboard.left_arrow #{args.inputs.keyboard.left_arrow}"
  args.outputs.debug << "   args.inputs.keyboard.right_arrow #{args.inputs.keyboard.right_arrow}"
  args.outputs.debug << "** Controller"
  args.outputs.debug << "   args.inputs.controller_one.dpad_left #{args.inputs.controller_one.dpad_left}"
  args.outputs.debug << "   args.inputs.controller_one.dpad_right #{args.inputs.controller_one.dpad_right}"
  args.outputs.debug << "   args.inputs.controller_one.left_analog_x_perc #{args.inputs.controller_one.left_analog_x_perc}"
end

`up_down` link

Returns -1 (down), 0 (neutral), or +1 (up). This method is aliased to args.inputs.up_down_with_wasd.

The following inputs are inspected to determine the result:

Keyboard's up/down arrow keys: args.inputs.keyboard.(up|down)_arrow
Keyboard's w, s keys (WASD): args.inputs.keyboard.(w|s)
Controller One's DPAD (if a controller is connected): args.inputs.controller_one.dpad_up, args.inputs.controller_one.dpad_down
Controller One's Up Analog (if a controller is connected): args.inputs.controller_one.up_analog_y_perc.abs >= 0.6

`up_down_directional` link

Returns -1 (down), 0 (neutral), or +1 (up). This method is aliased to args.inputs.up_down_arrow.

The following inputs are inspected to determine the result:

Keyboard's up/down arrow keys: args.inputs.keyboard.(up|down)_arrow
Controller One's DPAD (if a controller is connected): args.inputs.controller_one.dpad_up, args.inputs.controller_one.dpad_down
WASD and Controller One's Left Analog Stick are NOT consulted.

`up_down_perc` link

Returns a floating point value between -1 and 1. The following inputs are inspected to determine the result:

Controller One's Left Analog (if a controller is connected and the value is not 0.0): args.inputs.controller_one.up_analog_y_perc
If the left analog isn't being used, then Controller One's DPAD is consulted: args.inputs.controller_one.dpad_up, args.inputs.controller_one.dpad_down
Keyboard's up/down arrow keys: args.inputs.keyboard.(up|down)_arrow

Here is some sample code to help visualize the up_down functions.

def tick args
  args.outputs.debug << "* Variations of args.inputs.up_down"
  args.outputs.debug << "  args.inputs.up_down(_with_wasd) #{args.inputs.up_down}"
  args.outputs.debug << "  args.inputs.up_down_perc(_with_wasd) #{args.inputs.up_down_perc}"
  args.outputs.debug << "  args.inputs.up_down_directional #{args.inputs.up_down_directional}"
  args.outputs.debug << "  args.inputs.up_down_directional_perc #{args.inputs.up_down_directional_perc}"
  args.outputs.debug << "** Keyboard"
  args.outputs.debug << "   args.inputs.keyboard.w #{args.inputs.keyboard.w}"
  args.outputs.debug << "   args.inputs.keyboard.s #{args.inputs.keyboard.s}"
  args.outputs.debug << "   args.inputs.keyboard.up_arrow #{args.inputs.keyboard.up_arrow}"
  args.outputs.debug << "   args.inputs.keyboard.down_arrow #{args.inputs.keyboard.down_arrow}"
  args.outputs.debug << "** Controller"
  args.outputs.debug << "   args.inputs.controller_one.dpad_up #{args.inputs.controller_one.dpad_up}"
  args.outputs.debug << "   args.inputs.controller_one.dpad_down #{args.inputs.controller_one.dpad_down}"
  args.outputs.debug << "   args.inputs.controller_one.left_analog_y_perc #{args.inputs.controller_one.left_analog_y_perc}"
end

`text` link

Returns a string that represents the last key that was pressed on the keyboard.

Mouse (`args.inputs.mouse`) link

Represents the user's mouse.

`has_focus` link

Returns true if the game has mouse focus.

`x` link

Returns the current x location of the mouse.

`y` link

Returns the current y location of the mouse.

`previous_x` link

Returns the x location of the mouse on the previous frame.

`previous_y` link

Returns the y location of the mouse on the previous frame.

`relative_x` link

Returns the difference between the current x location of the mouse and its previous x location.

`relative_y` link

Returns the difference between the current y location of the mouse and its previous y location.

`inside_rect? rect` link

Return. args.inputs.mouse.inside_rect? takes in any primitive that responds to x, y, w, h:

`inside_circle? center_point, radius` link

Returns true if the mouse is inside of a specified circle. args.inputs.mouse.inside_circle? takes in any primitive that responds to x, y (which represents the circle's center), and takes in a radius:

`moved` link

Returns true if the mouse has moved on the current frame.

`button_left` link

Returns true if the left mouse button is down.

`button_middle` link

Returns true if the middle mouse button is down.

`button_right` link

Returns true if the right mouse button is down.

`button_bits` link

Returns a bitmask for all buttons on the mouse: 1 for a button in the down state, 0 for a button in the up state.

Here is a snippet to help visualize all mouse button states:

def tick args
  args.outputs.debug.watch "button_left:   #{inputs.mouse.button_left}"
  args.outputs.debug.watch "button_middle: #{inputs.mouse.button_middle}"
  args.outputs.debug.watch "button_right:  #{inputs.mouse.button_right}"
  args.outputs.debug.watch "button_bits:   #{inputs.mouse.button_bits.to_s(2)}"
end

`wheel` link

Represents the mouse wheel. Returns nil if no mouse wheel actions occurred. Otherwise args.inputs.mouse.wheel will return a Hash with x, and y (representing movement on each axis).

`click` OR `down`, `previous_click`, `up` link

The properties args.inputs.mouse.(click|down|previous_click|up) each return nil if the mouse button event didn't occur. And return an Entity that has an x, y properties along with helper functions to determine collision: inside_rect?, inside_circle. This value will be true if any of the mouse's buttons caused these events. To scope to a specific button use .button_left, .button_middle, .button_right, or .button_bits.

Touch link

The following touch apis are available on touch devices (iOS, Android, Mobile Web, Surface).

`args.inputs.touch` link

Returns a Hash representing all touch points on a touch device.

`args.inputs.finger_left` link

Returns a Hash with x and y denoting a touch point that is on the left side of the screen.

`args.inputs.finger_right` link

Returns a Hash with x and y denoting a touch point that is on the right side of the screen.

Controller (`args.inputs.controller_(one-four)`) link

Represents controllers connected to the usb ports. There is also args.inputs.controllers which returns controllers one through four as an array (args.inputs.controllers[0] points to args.inputs.controller_one).

`connected` link

Returns true if a controller is connected. If this value is false, controller properties will not be nil, but return 0 for directional based properties and false button state properties.

`name` link

String value representing the controller's name.

`active` link

Returns true if any of the controller's buttons were used.

`up` link

Returns true if up is pressed or held on the directional or left analog.

`down` link

Returns true if down is pressed or held on the directional or left analog.

`left` link

Returns true if left is pressed or held on the directional or left analog.

`right` link

Returns true if right is pressed or held on the directional or left analog.

`left_right` link

Returns -1 (left), 0 (neutral), or +1 (right) depending on results of args.inputs.controller_(one-four).left and args.inputs.controller_(one-four).right.

`up_down` link

Returns -1 (down), 0 (neutral), or +1 (up) depending on results of args.inputs.controller_(one-four).up and args.inputs.controller_(one-four).down.

`(left|right)_analog_x_raw` link

Returns the raw integer value for the analog's horizontal movement (-32,767 to +32,767).

`(left|right)_analog_y_raw` link

Returns the raw integer value for the analog's vertical movement (-32,767 to +32,767).

`(left|right)_analog_x_perc` link

Returns a number between -1 and 1 which represents the percentage the analog is moved horizontally as a ratio of the maximum horizontal movement.

`(left|right)_analog_y_perc` link

Returns a number between -1 and 1 which represents the percentage the analog is moved vertically as a ratio of the maximum vertical movement.

`dpad_up`, `directional_up` link

Returns true if up is pressed or held on the dpad.

`dpad_down`, `directional_down` link

Returns true if down is pressed or held on the dpad.

`dpad_left`, `directional_left` link

Returns true if left is pressed or held on the dpad.

`dpad_right`, `directional_right` link

Returns true if right is pressed or held on the dpad.

`(a|b|x|y|l1|r1|l2|r2|l3|r3|start|select)` link

Returns true if the specific button is pressed or held. Note: For PS4 and PS5 controllers a maps to Cross, b maps to Circle, x maps to Square, and y maps to Triangle.

`truthy_keys` link

Returns a collection of Symbols that represent all keys that are in the pressed or held state.

`key_down` link

Returns true if the specific button was pressed on this frame. args.inputs.controller_(one-four).key_down.BUTTON will only be true on the frame it was pressed.

`key_held` link

Returns true if the specific button is being held. args.inputs.controller_(one-four).key_held.BUTTON will be true for all frames after key_down (until released).

`key_up` link

Returns true if the specific button was released. args.inputs.controller_(one-four).key_up.BUTTON will be true only on the frame the button was released.

`left_analog_active?(threshold_raw:, threshold_perc:)` link

Returns true if the Left Analog Stick is tilted. The threshold_raw and threshold_perc are optional parameters that can be used to set the minimum threshold for the analog stick to be considered active. The threshold_raw is a number between 0 and 32,767, and the threshold_perc is a number between 0 and 1.

`right_analog_active?(threshold_raw:, threshold_perc:)` link

Returns true if the Right Analog Stick is tilted. The threshold_raw and threshold_perc are optional parameters that can be used to set the minimum threshold for the analog stick to be considered active. The threshold_raw is a number between 0 and 32,767, and the threshold_perc is a number between 0 and 1.

`key_down?(key)`, `key_up?(key)`, `key_held?(key)`, `key_down_or_held?(key)` link

Given a symbol, this returns true or false if the key is in the current state.

Here's how each of these methods are equivalent to key-based methods:

# key_down equivalent
args.inputs.controller_one.key_down.enter
args.inputs.controller_one.key_down?(:enter)

# key_up
args.inputs.controller_one.key_up.enter
args.inputs.controller_one.key_up?(:enter)

# key held
args.inputs.controller_one.key_held.enter
args.inputs.controller_one.key_held?(:enter)

# key down or held
args.inputs.controller_one.enter
args.inputs.controller_one.key_down_or_held?(:enter)

Keyboard (`args.inputs.keyboard`) link

Represents the user's keyboard.

`active` link

Returns Kernel.tick_count if any keys on the keyboard were pressed.

`has_focus` link

Returns true if the game has keyboard focus.

`up` link

Returns true if up or w is pressed or held on the keyboard.

`down` link

Returns true if down or s is pressed or held on the keyboard.

`left` link

Returns true if left or a is pressed or held on the keyboard.

`right` link

Returns true if right or d is pressed or held on the keyboard.

`left_right` link

Returns -1 (left), 0 (neutral), or +1 (right) depending on results of args.inputs.keyboard.left and args.inputs.keyboard.right.

`up_down` link

Returns -1 (left), 0 (neutral), or +1 (right) depending on results of args.inputs.keyboard.up and args.inputs.keyboard.up.

keyboard properties link

The following properties represent keys on the keyboard and are available on args.inputs.keyboard.KEY, args.inputs.keyboard.key_down.KEY, args.inputs.keyboard.key_held.KEY, and args.inputs.keyboard.key_up.KEY:

Here is an example showing all the ways to access a key's state:

def tick args
  # create a value in state to
  # track tick_count of the G key
  args.state.g_key ||= {
    ctrl_at: nil,
    key_down_at: nil,
    key_held_at: nil,
    key_down_or_held_at: nil,
    key_up_at: nil,
  }

  # for each keyboard event, capture the tick_count
  # that the event occurred
  # Ctrl + G
  if args.inputs.keyboard.ctrl_g
    args.state.g_key.ctrl_at = args.inputs.keyboard.ctrl_g
  end

  # G pressed/down
  if args.inputs.keyboard.key_down.g
    args.state.g_key.key_down_at = args.inputs.keyboard.key_down.g
  end

  # G held
  if args.inputs.keyboard.key_held.g
    args.state.g_key.key_held_at = args.inputs.keyboard.key_held.g
  end

  # G down or held
  if args.inputs.keyboard.g
    args.state.g_key.key_down_or_held_at = args.inputs.keyboard.g
  end

  # G up
  if args.inputs.keyboard.key_up.g
    args.state.g_key.key_up_at = args.inputs.keyboard.key_up.g
  end

  # display the tick_count of each event
  args.outputs.debug.watch "ctrl+g?         #{args.state.g_key.ctrl_at}"
  args.outputs.debug.watch "g down?         #{args.state.g_key.key_down_at}"
  args.outputs.debug.watch "g held?         #{args.state.g_key.key_held_at}"
  args.outputs.debug.watch "g down or held? #{args.state.g_key.key_down_or_held_at}"
  args.outputs.debug.watch "g up?           #{args.state.g_key.key_up_at}"
end

alt
meta
control, ctrl
shift
control_KEY, ctrl_KEY (dynamic method, eg args.inputs.keyboard.ctrl_a)
exclamation_point
zero - nine
backspace
delete
escape
enter
tab
(open|close)_round_brace
(open|close)_curly_brace
(open|close)_square_brace
colon
semicolon
equal
hyphen
space
dollar
percent
double_quotation_mark
single_quotation_mark
backtick
tilde
period
comma
pipe
underscore
ac_back (ac stands for Application Control, with ac_back representing Back button on a device (eg Android back button)
ac_home
ac_forward
ac_stop
ac_refresh
ac_bookmarks
a - z
w_scancode (key location for w in WASD layout across regions)
a_scancode (key location for a in WASD layout across regions)
s_scancode (key location for s in WASD layout across regions)
d_scancode (key location for d in WASD layout across regions)
shift
shift_left
shift_right
control, ctrl
control_left, ctrl_left
control_right, ctrl_right
alt, option
alt_left, option_left
alt_right, option_right
meta, command
meta_left, command_left
meta_right, command_right
left_arrow
right_arrow
up_arrow
down_arrow
left_arrow, left
right_arrow, right
up_arrow, up
down_arrow down
pageup
pagedown
plus
at
hash
forward_slash
back_slash
asterisk
less_than
greater_than
ampersand
superscript_two
caret
question_mark
section
ordinal_indicator
raw_key (unique numeric identifier for key)
caps_lock
f1
f2
f3
f4
f5
f6
f7
f8
f9
f10
f11
f12
print_screen
scroll_lock
pause
insert
home
page_up
delete
end
page_down
num_lock
kp_divide
kp_multiply
kp_minus
kp_plus
kp_enter
kp_one
kp_two
kp_three
kp_four
kp_five
kp_six
kp_seven
kp_eight
kp_nine
kp_zero
kp_period
kp_equals
left_right
up_down
directional_vector
truthy_keys (array of Symbols)

`keycodes` link

If the explicit named key isn't in the list above, you can still get the raw keycode via args.inputs.keyboard.key_(down|held|up).keycodes[KEYCODE_NUMBER]. The KEYCODE_NUMBER represents the keycode provided by SDL.

Here is a list SDL Keycodes: <https://wiki.libsdl.org/SDL2/SDLKeycodeLookup>

`char` link

Method is available under inputs.key_down, inputs.key_held, and inputs.key_up. Take note that

args.inputs.keyboard.key_held.char will only return the ascii value of the last key that was held. Use args.inputs.keyboard.key_held.truthy_keys to get an Array of Symbols representing all keys being held.

To get a picture of all key states args.inputs.keyboard.keys returns a Hash with the following keys: :down, :held, :down_or_held, :up.

NOTE: args.inputs.keyboard.key_down.char will be set in line with key repeat behavior of your OS.

This is a demonstration of the behavior (see ./samples/02_input_basics/01_keyboard for a more detailed example):

def tick args
  # uncomment the line below to see the value changes at a slower rate
  # $gtk.slowmo! 30

  keyboard = args.inputs.keyboard

  args.outputs.labels << { x: 30,
                           y: 720,
                           text: "use the J key to test" }

  args.outputs.labels << { x: 30,
                           y: 720 - 30,
                           text: "key_down.char: #{keyboard.key_down.char.inspect}" }

  args.outputs.labels << { x: 30,
                           y: 720 - 60,
                           text: "key_down.j:    #{keyboard.key_down.j}" }

  args.outputs.labels << { x: 30,
                           y: 720 - 30,
                           text: "key_held.char: #{keyboard.key_held.char.inspect}" }

  args.outputs.labels << { x: 30,
                           y: 720 - 60,
                           text: "key_held.j:    #{keyboard.key_held.j}" }

  args.outputs.labels << { x: 30,
                           y: 720 - 30,
                           text: "key_up.char:   #{keyboard.key_up.char.inspect}" }

  args.outputs.labels << { x: 30,
                           y: 720 - 60,
                           text: "key_up.j:      #{keyboard.key_up.j}" }
end

`key_down?(key)`, `key_up?(key)`, `key_held?(key)`, `key_down_or_held?(key)` link

Given a symbol, this returns true or false if the key is in the current state.

Here's how each of these methods are equivalent to key-based methods:

# key_down equivalent
args.inputs.keyboard.key_down.enter
args.inputs.keyboard.key_down?(:enter)

# key_up
args.inputs.keyboard.key_up.enter
args.inputs.keyboard.key_up?(:enter)

# key held
args.inputs.keyboard.key_held.enter
args.inputs.keyboard.key_held?(:enter)

# key down or held
args.inputs.keyboard.enter
args.inputs.keyboard.key_down_or_held?(:enter)

The following

`keys` link

Returns a Hash with all keys on the keyboard in their respective state. The Hash contains the following keys

:down
:held
:down_or_held
:up

Runtime (`args.gtk`) link

The GTK::Runtime class is the core of DragonRuby.

?> All functions $gtk, GTK, or inside of the tick method through args.

def tick args
  args.gtk.function(...)

  # OR available globally
  $gtk.function(...)
  # OR
  GTK.function(...)
end

Class Macros link

The following class macros are available within DragonRuby.

`attr` link

The attr class macro is an alias to attr_accessor.

Instead of:

class Player
  attr_accessor :hp, :armor
end

You can do:

class Player
  attr :hp, :armor
end

`attr_gtk` link

As the size/complexity of your game increases. You may want to create classes to organize everything. The attr_gtk class macro adds DragonRuby's environment methods (such as args.state, args.inputs, args.outputs, args.audio, etc) to your class so you don't have to pass args around everywhere.

Instead of:

class Game
  def tick args
    defaults args
    calc args
    render args
  end

  def defaults args
    args.state.space_pressed_at ||= 0
  end

  def calc args
    if args.inputs.keyboard.key_down.space
      args.state.space_pressed_at = Kernel.tick_count
    end
  end

  def render args
    if args.state.space_pressed_at == 0
      args.outputs.labels << { x: 100, y: 100,
                               text: "press space" }
    else
      args.outputs.labels << { x: 100, y: 100,
                               text: "space was pressed at: #{args.state.space_pressed_at}" }
    end
  end
end

def tick args
  $game ||= Game.new
  $game.tick args
end

You can do:

class Game
  attr_gtk # attr_gtk class macro

  def tick
    defaults
    calc
    render
  end

  def defaults
    state.space_pressed_at ||= 0
  end

  def calc
    if inputs.keyboard.key_down.space
      state.space_pressed_at = Kernel.tick_count
    end
  end

  def render
    if state.space_pressed_at == 0
      outputs.labels << { x: 100, y: 100,
                          text: "press space" }
    else
      outputs.labels << { x: 100, y: 100,
                          text: "space was pressed at: #{state.space_pressed_at}" }
    end
  end
end

def tick args
  $game ||= Game.new
  $game.args = args # set args property on game
  $game.tick        # call tick without passing in args
end

$game = nil

Indie and Pro Functions link

The following functions are only available at the Indie and Pro License tiers.

`get_pixels` link

Given a file_path to a sprite, this function returns a Hash with w, h, and pixels. The pixels key contains an array of hexadecimal values representing the ABGR of each pixel in a sprite with item 0 representing the top left corner of the png.

Here's an example of how to get the color data for a pixel:

def tick args
  # load the pixels from the image
  args.state.image ||= args.gtk.get_pixels "sprites/square/blue.png"

  # initialize state variables for the pixel coordinates
  args.state.x_px ||= 0
  args.state.y_px ||= 0

  sprite_pixels = args.state.image.pixels
  sprite_h = args.state.image.h
  sprite_w = args.state.image.w

  # move the pixel coordinates using keyboard
  args.state.x_px += args.inputs.left_right
  args.state.y_px += args.inputs.up_down

  # get pixel at the current coordinates
  args.state.x_px = args.state.x_px.clamp(0, sprite_w - 1)
  args.state.y_px = args.state.y_px.clamp(0, sprite_h - 1)
  row = sprite_h - args.state.y_px - 1
  col = args.state.x_px
  abgr = sprite_pixels[sprite_h * row + col]
  a = (abgr >> 24) & 0xff
  b = (abgr >> 16) & 0xff
  g = (abgr >> 8) & 0xff
  r = (abgr >> 0) & 0xff

  # render debug information
  args.outputs.debug << "row: #{row} col: #{col}"
  args.outputs.debug << "pixel entry 0: rgba #{r} #{g} #{b} #{a}"

  # render the sprite plus crosshairs
  args.outputs.sprites << { x: 0, y: 0, w: 80, h: 80, path: "sprites/square/blue.png" }
  args.outputs.lines << { x: args.state.x_px, y: 0, h: 720 }
  args.outputs.lines << { x: 0, y: args.state.y_px, w: 1280 }
end

See the following sample apps for how to use pixel arrays:

./samples/07_advanced_rendering/06_pixel_arrays
./samples/07_advanced_rendering/06_pixel_arrays_from_file

`dlopen` link

Loads a precompiled C Extension into your game.

See the sample apps at ./samples/12_c_extensions for detailed walkthroughs of creating C extensions.

Environment and Utility Functions link

The following functions will help in interacting with the OS and rendering pipeline.

`calcstringbox` link

Returns the render width and render height as a tuple for a piece of text. The parameters this method takes are:

text: the text you want to get the width and height of.
size_enum: number representing the render size for the text. This parameter is optional and defaults to 0 which represents a baseline font size in units specific to DragonRuby (a negative value denotes a size smaller than what would be comfortable to read on a handheld device positive values above 0 represent larger font sizes).
font: path to a font file that the width and height will be based off of. This field is optional and defaults to the DragonRuby's default font.

def tick args
  text = "a piece of text"
  size_enum = 5 # "large font size"

  # path is relative to your game directory (eg mygame/fonts/courier-new.ttf)
  font = "fonts/courier-new.ttf"

  # get the render width and height
  string_w, string_h = args.gtk.calcstringbox text, size_enum, font

  # render the label
  args.outputs.labels << {
    x: 100,
    y: 100,
    text: text,
    size_enum: size_enum,
    font: font
  }

  # render a border around the label based on the results from calcstringbox
  args.outputs.borders << {
    x: 100,
    y: 100,
    w: string_w,
    h: string_h,
    r: 0,
    g: 0,
    b: 0
  }
end

calcstringbox also supports named parameters for size_enum and size_px.

  # size_enum, and font named parameters
  string_w, string_h = args.gtk.calcstringbox text, size_enum: 0, font: "fonts/example.ttf"

  # size_px, and font named parameters
  string_w, string_h = args.gtk.calcstringbox text, size_px: 20, font: "fonts/example.ttf"

`request_quit` link

Call this function to exit your game. You will be given one additional tick if you need to perform any housekeeping before that game closes.

def tick args
  # exit the game after 600 frames (10 seconds)
  if Kernel.tick_count == 600
    args.gtk.request_quit
  end
end

`quit_requested?` link

This function will return true if the game is about to exit (either from the user closing the game or if request_quit was invoked).

`set_window_fullscreen` link

This function takes in a single boolean parameter. true to make the game fullscreen, false to return the game back to windowed mode.

def tick args
  # make the game full screen after 600 frames (10 seconds)
  if Kernel.tick_count == 600
    args.gtk.set_window_fullscreen true
  end

  # return the game to windowed mode after 20 seconds
  if Kernel.tick_count == 1200
    args.gtk.set_window_fullscreen false
  end
end

`window_fullscreen?` link

Returns true if the window is currently in fullscreen mode.

`set_window_scale` link

The first parameter is a float value used to resize the game window to a percentage of 1280x720 (or 720x1280 in portrait mode). The valid scale options are 0.1, 0.25, 0.5, 0.75, 1.25, 1.5, 2.0, 2.5, 3.0, and 4.0. The float value you pass in will be floored to the nearest valid scale option.

The second and third parameters are optional and default to 16 and 9 (representing with width and height aspect ratios for the window). Providing these parameters will resize the window with the non-standard aspect ratio. This is useful for testing letter-boxing and All Screen modes (Pro feature).

Setting the window scale to the following will give a good representation of your game on various form factors.

# how your game will look on an iPad
$gtk.set_window_scale 1.0, 4, 3

# how your game will look on a wide aspect ratio
$gtk.set_window_scale 1.0, 21, 9

`set_window_title` link

This function takes in a string updates the title of the game in the Menu Bar.

Note: The default title for your game is specified in via the gametitle property in mygame/metadata/game_metadata.txt.

`platform?` link

You can ask DragonRuby which platform your game is currently being run on. This can be useful if you want to perform different pieces of logic based on where the game is running.

The raw platform string value is available via args.gtk.platform which takes in a symbol representing the platform's categorization/mapping.

You can see all available platform categorizations via the args.gtk.platform_mappings function.

Here's an example of how to use args.gtk.platform? category_symbol:

def tick args
  label_style = { x: 640, y: 360, anchor_x: 0.5, anchor_y: 0.5 }
  if    args.gtk.platform? :macos
    args.outputs.labels << { text: "I am running on MacOS.", **label_style }
  elsif args.gtk.platform? :win
    args.outputs.labels << { text: "I am running on Windows.", **label_style }
  elsif args.gtk.platform? :linux
    args.outputs.labels << { text: "I am running on Linux.", **label_style }
  elsif args.gtk.platform? :web
    args.outputs.labels << { text: "I am running on a web page.", **label_style }
  elsif args.gtk.platform? :android
    args.outputs.labels << { text: "I am running on Android.", **label_style }
  elsif args.gtk.platform? :ios
    args.outputs.labels << { text: "I am running on iOS.", **label_style }
  elsif args.gtk.platform? :touch
    args.outputs.labels << { text: "I am running on a device that supports touch (either iOS/Android native or mobile web).", **label_style }
  elsif args.gtk.platform? :steam
    args.outputs.labels << { text: "I am running via steam (covers both desktop and steamdeck).", **label_style }
  elsif args.gtk.platform? :steam_deck
    args.outputs.labels << { text: "I am running via steam on the Steam Deck (not steam desktop).", **label_style }
  elsif args.gtk.platform? :steam_desktop
    args.outputs.labels << { text: "I am running via steam on desktop (not steam deck).", **label_style }
  end
end

`production?` link

Returns true if the game is being run in a released/shipped state.

If you want to simulate a production build. Add an empty file called dragonruby_production_build inside of the metadata folder. This will turn of all logging and all creation of temp files used for development purposes.

`platform_mappings` link

These are the current platform categorizations (args.gtk.platform_mappings):

{
  "Mac OS X"   => [:desktop, :macos, :osx, :mac, :macosx], # may also include :steam and :steam_desktop run via steam
  "Windows"    => [:desktop, :windows, :win],              # may also include :steam and :steam_desktop run via steam
  "Linux"      => [:desktop, :linux, :nix],                # may also include :steam and :steam_desktop run via steam
  "Emscripten" => [:web, :wasm, :html, :emscripten],       # may also include :touch if running in the web browser on mobile
  "iOS"        => [:mobile, :ios, :touch],
  "Android"    => [:mobile, :android, :touch],
  "Steam Deck" => [:steamdeck, :steam_deck, :steam],
}

Given the mappings above, args.gtk.platform? :desktop would return true if the game is running on a player's computer irrespective of OS (MacOS, Linux, and Windows are all categorized as :desktop platforms).

`open_url` link

Given a uri represented as a string. This function will open the uri in the user's default browser.

def tick args
  # open a url after 600 frames (10 seconds)
  if Kernel.tick_count == 600
    args.gtk.open_url "http://dragonruby.org"
  end
end

`system` link

Given an OS dependent cli command represented as a string, this function executes the command and puts the results to the DragonRuby Console (returns nil).

def tick args
  # execute ls on the current directory in 10 seconds
  if Kernel.tick_count == 600
    args.gtk.system "ls ."
  end
end

`exec` link

Given an OS dependent cli command represented as a string, this function executes the command and returns a string representing the results.

def tick args
  # execute ls on the current directory in 10 seconds
  if Kernel.tick_count == 600
    results = args.gtk.exec "ls ."
    puts "The results of the command are:"
    puts results
  end
end

`show_cursor` link

Shows the mouse cursor.

`hide_cursor` link

Hides the mouse cursor.

`cursor_shown?` link

Returns true if the mouse cursor is visible.

`set_mouse_grab` link

Takes in a numeric parameter representing the mouse grab mode.

0: Ungrabs the mouse.
1: Grabs the mouse.
2: Hides the cursor, grabs the mouse and puts it in relative position mode accessible via args.inputs.mouse.relative_(x|y).

`set_system_cursor` link

Takes in a string value of "arrow", "ibeam", "wait", or "hand" and sets the mouse cursor to the corresponding system cursor (if available on the OS).

`set_cursor` link

Replaces the mouse cursor with a sprite. Takes in a path to the sprite, and optionally an x and y value representing the relative positioning the sprite will have to the mouse cursor.

def tick args
  if Kernel.tick_count == 0
    # assumes a sprite of size 80x80 and centers the sprite
    # relative to the cursor position.
    args.gtk.set_cursor "sprites/square/blue.png", 40, 40
  end
end

File IO Functions link

The following functions give you the ability to interact with the file system.

DragonRuby uses a sandboxed filesystem which will automatically read from and write to a location appropriate for your platform so you don't have to worry about theses details in your code. You can just use $gtk.read_file, $gtk.write_file, and $gtk.append_file with a relative path and the engine will take care of the rest.

The data directories that will be written to in a production build are:

Windows: C:\Users\YourWindowsUsername\AppData\Roaming\[devtitle]\[gametitle]
MacOS: $HOME/Library/Application Support/[gametitle]
Linux: $HOME/.local/share/[gametitle]
HTML5: The data will be written to the browser's IndexedDB.

The values in square brackets are the values you set in your app/metadata/game_metadata.txt file.

When running a development build you will directly write to your game directory (and thus overwrite existing files). This can be useful for built-in development tools like level editors.

For more details on the implementation of the sandboxed filesystem, see Ryan C. Gordon's PhysicsFS documentation: [https://icculus.org/physfs/](https://icculus.org/physfs/)

NOTE:

File access functions are sandboxed and assume that the dragonruby binary lives alongside the game you are building. --Do not expect these functions to return correct values if you are attempting to run the dragonruby binary from a shared location--. It's --strongly-- recommended that the directory structure contained in the zip is not altered and games are built using that starter template.

`list_files` link

This function takes in one parameter. The parameter is the directory path and assumes the the game directory is the root. The method returns an Array of String representing all files within the directory. Use stat_file to determine whether a specific path is a file or a directory.

`stat_file` link

This function takes in one parameter. The parameter is the file path and assumes the the game directory is the root. The method returns nil if the file doesn't exist otherwise it returns a Hash with the following information:

# {
#   path: String,
#   file_size: Int,
#   mod_time: Int,
#   create_time: Int,
#   access_time: Int,
#   readonly: Boolean,
#   file_type: Symbol (:regular, :directory, :symlink, :other),
# }

def tick args
  if args.inputs.mouse.click
    args.gtk.write_file "last-mouse-click.txt", "Mouse was clicked at #{Kernel.tick_count}."
  end

  file_info = args.gtk.stat_file "last-mouse-click.txt"

  if file_info
    args.outputs.labels << {
      x: 30,
      y: 30.from_top,
      text: file_info.to_s,
      size_enum: -3
    }
  else
    args.outputs.labels << {
      x: 30,
      y: 30.from_top,
      text: "file does not exist, click to create file",
      size_enum: -3
    }
  end
end

`read_file` link

Given a file path, a string will be returned representing the contents of the file. nil will be returned if the file does not exist. You can use stat_file to get additional information of a file.

`write_file` link

This function takes in two parameters. The first parameter is the file path and assumes the the game directory is the root. The second parameter is the string that will be written. The method ----overwrites---- whatever is currently in the file. Use append_file to append to the file as opposed to overwriting.

def tick args
  if args.inputs.mouse.click
    args.gtk.write_file "last-mouse-click.txt", "Mouse was clicked at #{Kernel.tick_count}."
  end
end

`append_file` link

This function takes in two parameters. The first parameter is the file path and assumes the the game directory is the root. The second parameter is the string that will be written. The method appends to whatever is currently in the file (a new file is created if one does not already exist). Use write_file to overwrite the file's contents as opposed to appending.

def tick args
  if args.inputs.mouse.click
    args.gtk.append_file "click-history.txt", "Mouse was clicked at #{Kernel.tick_count}.\n"
    puts args.gtk.read_file("click-history.txt")
  end
end

`delete_file` link

This function takes in a single parameters. The parameter is the file or directory path that should be deleted. This function will raise an exception if the path requesting to be deleted does not exist.

Here is a list of reasons an exception could be raised:

If the path is still open (for reading or writing).
If the path is not a file or directory.
If the path is a circular symlink.
If you do not have permissions to delete the path.
If the directory attempting to be deleted is not empty.

Notes:

Use stat_file to determine if a path exists.
Use list_files to determine if a directory is empty.
You cannot delete files outside of your sandboxed game environment.

def tick args
  if args.inputs.keyboard.key_down.w
    # press w to write file
    args.gtk.append_file "example-file.txt", "File written at #{Kernel.tick_count}\n"
    args.gtk.notify "File written/appended."
  elsif args.inputs.keyboard.key_down.d
    # press d to delete file "unsafely"
    args.gtk.delete_file "example-file.txt"
    args.gtk.notify "File deleted."
  elsif args.inputs.keyboard.key_down.r
    # press r to read file
    contents = args.gtk.read_file "example-file.txt"
    args.gtk.notify "File contents written to console."
    puts contents
  end
end

`parse_json` link

Given a json string, this function returns a hash representing the json data.

hash = args.gtk.parse_json '{ "name": "John Doe", "aliases": ["JD"] }'
# structure of hash: { "name"=>"John Doe", "aliases"=>["JD"] }

`parse_json_file` link

Same behavior as parse_json_file except a file path is read for the json string.

`parse_xml` link

Given xml data as a string, this function will return a hash that represents the xml data in the following recursive structure:

{
  type: :element,
  name: "Person",
  children: [...]
}

`parse_xml_file` link

Function has the same behavior as parse_xml except that the parameter must be a file path that contains xml contents.

Network IO Functions link

The following functions help with interacting with the network.

`http_get` link

Returns an object that represents an http response which will eventually have a value. This http_get method is invoked asynchronously. Check for completion before attempting to read results.

def tick args
  # perform an http get and print the response when available
  args.state.result ||= args.gtk.http_get "https://httpbin.org/html"

  if args.state.result && args.state.result[:complete] && !args.state.printed
    if args.state.result[:http_response_code] == 200
      puts "The response was successful. The body is:"
      puts args.state.result[:response_data]
    else
      puts "The response failed. Status code:"
      puts args.state.result[:http_response_code]
    end
    # set a flag denoting that the response has been printed
    args.state.printed = true

    # show the console
    args.gtk.show_console
  end
end

`http_post` link

Returns an object that represents an http response which will eventually have a value. This http_post method is invoked asynchronously. Check for completion before attempting to read results.

First parameter: The url to send the request to.
Second parameter: Hash that represents form fields to send.
Third parameter: Headers. Note: Content-Type must be form encoded flavor. If you are unsure of what to pass in, set the content type to application/x-www-form-urlencoded

def tick args
  # perform an http get and print the response when available

  args.state.form_fields ||= { "userId" => "#{Time.now.to_i}" }
  args.state.result ||= args.gtk.http_post "http://httpbin.org/post",
                                           args.state.form_fields,
                                           ["Content-Type: application/x-www-form-urlencoded"]


  if args.state.result && args.state.result[:complete] && !args.state.printed
    if args.state.result[:http_response_code] == 200
      puts "The response was successful. The body is:"
      puts args.state.result[:response_data]
    else
      puts "The response failed. Status code:"
      puts args.state.result[:http_response_code]
    end
    # set a flag denoting that the response has been printed
    args.state.printed = true

    # show the console
    args.gtk.show_console
  end
end

`http_post_body` link

Returns an object that represents an http response which will eventually have a value. This http_post_body method is invoked asynchronously. Check for completion before attempting to read results.

First parameter: The url to send the request to.
Second parameter: String that represents the body that will be sent
Third parameter: Headers. Be sure to populate the Content-Type that matches the data you are sending.

def tick args
  # perform an http get and print the response when available

  args.state.json ||= "{ "userId": "#{Time.now.to_i}"}"
  args.state.result ||= args.gtk.http_post_body "http://httpbin.org/post",
                                                args.state.json,
                                                ["Content-Type: application/json", "Content-Length: #{args.state.json.length}"]


  if args.state.result && args.state.result[:complete] && !args.state.printed
    if args.state.result[:http_response_code] == 200
      puts "The response was successful. The body is:"
      puts args.state.result[:response_data]
    else
      puts "The response failed. Status code:"
      puts args.state.result[:http_response_code]
    end
    # set a flag denoting that the response has been printed
    args.state.printed = true

    # show the console
    args.gtk.show_console
  end
end

`start_server!` link

Starts a in-game http server that can be process http requests. When your game is running in development mode. A dev server is started at http://localhost:9001

?> You must set webserver.enabled=true in metadata/cvars.txt to view docs locally. These docs are also available under ./docs within the zip file in markdown format.

You can start an in-game http server in production via:

def tick args
  # server explicitly enabled in production
  args.gtk.start_server! port: 9001, enable_in_prod: true
end

Here's how you would respond to http requests:

def tick args
  # server explicitly enabled in production
  args.gtk.start_server! port: 9001, enable_in_prod: true

  # loop through pending requests and respond to them
  args.inputs.http_requests.each do |request|
    puts "#{request}"
    request.respond 200, "ok"
  end
end

`http_get` link

Returns an object that represents an http response which will eventually have a value. This http_get method is invoked asynchronously. Check for completion before attempting to read results.

def tick args
  # perform an http get and print the response when available
  args.state.result ||= args.gtk.http_get "https://httpbin.org/html"

  if args.state.result && args.state.result[:complete] && !args.state.printed
    if args.state.result[:http_response_code] == 200
      puts "The response was successful. The body is:"
      puts args.state.result[:response_data]
    else
      puts "The response failed. Status code:"
      puts args.state.result[:http_response_code]
    end
    # set a flag denoting that the response has been printed
    args.state.printed = true

    # show the console
    args.gtk.show_console
  end
end

`http_post` link

Returns an object that represents an http response which will eventually have a value. This http_post method is invoked asynchronously. Check for completion before attempting to read results.

First parameter: The url to send the request to.
Second parameter: Hash that represents form fields to send.
Third parameter: Headers. Note: Content-Type must be form encoded flavor. If you are unsure of what to pass in, set the content type to application/x-www-form-urlencoded

def tick args
  # perform an http get and print the response when available

  args.state.form_fields ||= { "userId" => "#{Time.now.to_i}" }
  args.state.result ||= args.gtk.http_post "http://httpbin.org/post",
                                           args.state.form_fields,
                                           ["Content-Type: application/x-www-form-urlencoded"]


  if args.state.result && args.state.result[:complete] && !args.state.printed
    if args.state.result[:http_response_code] == 200
      puts "The response was successful. The body is:"
      puts args.state.result[:response_data]
    else
      puts "The response failed. Status code:"
      puts args.state.result[:http_response_code]
    end
    # set a flag denoting that the response has been printed
    args.state.printed = true

    # show the console
    args.gtk.show_console
  end
end

`http_post_body` link

Returns an object that represents an http response which will eventually have a value. This http_post_body method is invoked asynchronously. Check for completion before attempting to read results.

First parameter: The url to send the request to.
Second parameter: String that represents the body that will be sent
Third parameter: Headers. Be sure to populate the Content-Type that matches the data you are sending.

def tick args
  # perform an http get and print the response when available

  args.state.json ||= "{ "userId": "#{Time.now.to_i}"}"
  args.state.result ||= args.gtk.http_post_body "http://httpbin.org/post",
                                                args.state.json,
                                                ["Content-Type: application/json", "Content-Length: #{args.state.json.length}"]


  if args.state.result && args.state.result[:complete] && !args.state.printed
    if args.state.result[:http_response_code] == 200
      puts "The response was successful. The body is:"
      puts args.state.result[:response_data]
    else
      puts "The response failed. Status code:"
      puts args.state.result[:http_response_code]
    end
    # set a flag denoting that the response has been printed
    args.state.printed = true

    # show the console
    args.gtk.show_console
  end
end

`start_server!` link

Starts a in-game http server that can be process http requests. When your game is running in development mode. A dev server is started at http://localhost:9001

?> You must set webserver.enabled=true in metadata/cvars.txt to view docs locally. These docs are also available under ./docs within the zip file in markdown format.

You can start an in-game http server in production via:

def tick args
  # server explicitly enabled in production
  args.gtk.start_server! port: 9001, enable_in_prod: true
end

Here's how you would respond to http requests:

def tick args
  # server explicitly enabled in production
  args.gtk.start_server! port: 9001, enable_in_prod: true

  # loop through pending requests and respond to them
  args.inputs.http_requests.each do |request|
    puts "#{request}"
    request.respond 200, "ok"
  end
end

Developer Support Functions link

The following functions help support the development process. It is not recommended to use this functions in "production" game logic.

`version` link

Returns a string representing the version of DragonRuby you are running.

`version_pro?` link

Returns true if the version of DragonRuby is NOT Standard Edition.

`game_version` link

Returns a version string within mygame/game_metadata.txt.

To get other values from mygame/game_metadata.txt, you can do:

def tick args
  if Kernel.tick_count == 0
    puts args.gtk.game_version
    args.cvars["game_metadata.version"].value
  end
end

`reset` link

This function will be called if $gtk.reset is invoked. It will be called before DragonRuby resets game state and is useful for capturing state information before a reset occurs (you can use this override to reset state external to DragonRuby's args.state construct).

# class that handles your game loop
class MyGame
  attr :foo

  # initialization method that sets member variables
  # external to args.state
  def initialize args
    puts "initializing game"
    @foo = 0
    args.state.bar ||= 0
  end

  # game logic
  def tick args
    args.state.bar += 1
    @foo += 1
    args.outputs.labels << {
      x: 640,
      y: 360,
      text: "#{$game.foo}, #{args.state.bar}"
    }
  end
end

def tick args
  # initialize global game variable if it's nil
  $game ||= MyGame.new(args)

  # run tick
  $game.tick args

  # at T=600, invoke reset
  if Kernel.tick_count == 600
    $gtk.reset
  end
end

# this function will be invoked before
# $gtk.reset occurs
def reset args
  puts "resetting"
  puts "foo is: #{$game.foo}"
  puts "bar is: #{args.state.bar}"
  puts "tick count: #{Kernel.tick_count}"

  # reset global game to nil so that it will be re-initialized next tick
  $game = nil
end

`reset_next_tick` link

Has the same behavior as reset except the reset occurs before tick is executed again. reset resets the environment immediately (while the tick method is in-flight). It's recommended that reset should be called outside of the tick method (invoked when a file is saved/hotloaded), and reset_next_tick be used inside of the tick method so you don't accidentally blow away state the your game depends on to complete the current tick without exceptions.

def tick args
  # reset the game if "r" is pressed on the keyboard
  if args.inputs.keyboard.key_down.r
    args.gtk.reset_next_tick # use reset_next_tick instead of reset
  end
end

# reset the game if this file is hotloaded/required
# (removes the need to press "r" when I file is updated)
$gtk.reset

`reset_sprite` link

Sprites when loaded are cached. Given a string parameter, this method invalidates the cache record of a sprite so that updates on from the disk can be loaded.

This function can also be used to delete/garbage collect render targets you are no longer using.

`reset_sprites` link

Sprites when loaded are cached. This method invalidates the cache record of all sprites so that updates on from the disk can be loaded. This function is automatically called when args.gtk.reset ($gtk.reset) is invoked.

`calcspritebox` link

Given a path to a sprite, this method returns the width and height of a sprite as a tuple.

NOTE: This method should be used for development purposes only and is expensive to call every frame. Do not use this method to set the size of sprite when rendering (hard code those values since you know what they are beforehand).

`current_framerate` link

Returns a float value representing the framerate of your game. This is an approximation/moving average of your framerate and should eventually settle to 60fps.

def tick args
  # render a label to the screen that shows the current framerate
  # formatted as a floating point number with two decimal places
  args.outputs.labels << { x: 30, y: 30.from_top, text: "#{args.gtk.current_framerate.to_sf}" }
end

`framerate_diagnostics_primitives` link

Returns a set of primitives that can be rendered to the screen which provide more detailed information about the speed of your simulation (framerate, draw call count, mouse position, etc).

def tick args
  args.outputs.primitives << args.gtk.framerate_diagnostics_primitives
end

`warn_array_primitives!` link

This function helps you audit your game of usages of array-based primitives. While array-based primitives are simple to create and use, they are slower to process than Hash or Class based primitives.

def tick args
  # enable array based primitives warnings
  args.gtk.warn_array_primitives!

  # array-based primitive elsewhere in code
  # an log message will be posted giving the location of the array
  # based primitive usage
  args.outputs.sprites << [100, 100, 200, 200, "sprites/square/blue.png"]

  # instead of using array based primitives, migrate to hashes as needed
  args.outputs.sprites << {
    x: 100,
    y: 100,
    w: 200,
    h: 200, path:
    "sprites/square/blue.png"
  }
end

`benchmark` link

You can use this function to compare the relative performance of blocks of code.

Function takes in either iterations or seconds along with a collection of lambdas.

If iterations is provided, the winner will be determined by the fastest completion time.

If seconds is provided, the winner will be determined by the most completed iterations.

def tick args
  # press i to run benchmark using iterations
  if args.inputs.keyboard.key_down.i
    args.gtk.console.show
    args.gtk.benchmark iterations: 1000, # number of iterations
                       # label for experiment
                       using_numeric_map: -> () {
                         # experiment body
                         v = 100.map_with_index do |i|
                           i * 100
                         end
                       },
                       # label for experiment
                       using_numeric_times: -> () {
                         # experiment body
                         v = []
                         100.times do |i|
                           v << i * 100
                         end
                       }
  end

  # press s to run benchmark using seconds
  if args.inputs.keyboard.key_down.s
    args.gtk.console.show
    args.gtk.benchmark seconds: 1, # number of seconds to run each experiment
                       # label for experiment
                       using_numeric_map: -> () {
                         # experiment body
                         v = 100.map_with_index do |i|
                           i * 100
                         end
                       },
                       # label for experiment
                       using_numeric_times: -> () {
                         # experiment body
                         v = []
                         100.times do |i|
                           v << i * 100
                         end
                       }
  end
end

`notify!` link

Given a string, this function will present a message at the bottom of your game. This method is only invoked in dev mode and is useful for debugging.

An optional parameter of duration (number value representing ticks) can also be passed in. The default value if 300 ticks (5 seconds).

def tick args
  if args.inputs.mouse.click
    args.gtk.notify! "Mouse was clicked!"
  end

  if args.inputs.keyboard.key_down.r
    # optional duration parameter
    args.gtk.notify! "R key was pressed!", 600 # present message for 10 seconds/600 frames
  end
end

`notify_extended!` link

Has similar behavior as notify! except you have additional options to show messages in a production environment.

def tick args
  if args.inputs.mouse.click
    args.gtk.notify_extended! message: "message",
                              duration: 300,
                              env: :prod
  end
end

`slowmo!` link

Given a numeric value representing the factor of 60fps. This function will bring your simulation loop down to slower rate. This method is intended to be used for debugging purposes.

def tick args
  # set your simulation speed to (15 fps): args.gtk.slowmo! 4
  # set your simulation speed to (1 fps): args.gtk.slowmo! 60
  # set your simulation speed to (30 fps):
  args.gtk.slowmo! 2
end

Remove this line from your tick method will automatically set your simulation speed back to 60 fps.

`show_console` link

Shows the DragonRuby console. Useful when debugging/customizing an in-game dev workflow.

`hide_console` link

Shows the DragonRuby console. Useful when debugging/customizing an in-game dev workflow.

`enable_console` link

Enables the DragonRuby Console so that it can be presented by pressing the tilde key (the key next to the number 1 key).

`disable_console` link

Disables the DragonRuby Console so that it won't show up even if you press the tilde key or call args.gtk.show_console.

`disable_reset_via_ctrl_r` link

By default, pressing CTRL+R invokes $gtk.reset_next_tick (safely resetting your game with a convenient key combo).

If you want to disable this behavior, add the following to the main.rb:

def tick args
  ...
end

$gtk.disable_reset_via_ctrl_r

NOTE: $gtk.disable_console will also disable the CTRL+R reset behavior.

`disable_controller_config` link

DragonRuby has a built-in controller configuration/mapping wizard. You can disable this wizard by adding $gtk.disable_controller_config at the top of main.rb.

`enable_controller_config` link

DragonRuby has a built-in controller configuration/mapping wizard. You can re-enable this wizard by adding $gtk.enable_controller_config at the top of main.rb (this is enabled by default).

`start_recording` link

Resets the game to tick 0 and starts recording gameplay. Useful for visual regression tests/verification.

`stop_recording` link

Function takes in a destination file for the currently recording gameplay. This file can be used to replay a recording.

`cancel_recording` link

Function cancels a gameplay recording session and discards the replay.

`start_replay` link

Given a file that represents a recording, this method will run the recording against the current codebase.

You can start a replay from the command line also:

# first argument: the game directory
# --replay switch is the file path relative to the game directory
# --speed switch is optional. a value of 4 will run the replay and game at 4x speed
# cli command example is in the context of Linux and Mac, for Windows the binary would be ./dragonruby.exe
./dragonruby ./mygame --replay replay.txt --speed 4

`stop_replay` link

Function stops a replay that is currently executing.

`get_base_dir` link

Returns the path to the location of the dragonruby binary. In production mode, this value will be the same as the value returned by get_game_dir. Function should only be used for debugging/development workflows.

`get_game_dir` link

Returns the location within sandbox storage that the game is running. When developing your game, this value will be your mygame directory. In production, it'll return a value that is OS specific (eg the Roaming directory on Windows or the Application Support directory on Mac).

Invocations of (write|append)_file will write to this sandboxed directory.

`get_game_dir_url` link

Returns a url encoded string representing the sandbox location for game data.

`open_game_dir` link

Opens the game directory in the OS's file explorer. This should be used for debugging purposes only.

`write_file_root` link

Given a file path and contents, the contents will be written to a directory outside of the game directory. This method should be used for development purposes only. In production this method will write to the same sandboxed location as write_file.

`append_file_root` link

Has the same behavior as write_file_root except that it appends the contents as opposed to overwriting them.

`argv` link

Returns a string representing the command line arguments passed to the DragonRuby binary. This should be used for development/debugging purposes only.

`cli_arguments` link

Returns a Hash for command line arguments in the format of --switch value (two hyphens preceding the switch flag with the value separated by a space). This should be used for development/debugging purposes only.

`download_stb_rb(_raw)` link

These two functions can help facilitate the integration of external code files. OSS contributors are encouraged to create libraries that all fit in one file (lowering the barrier to entry for adoption).

Examples:

def tick args
end

# option 1:
# source code will be downloaded from the specified GitHub url, and saved locally with a
# predefined folder convention.
$gtk.download_stb_rb "https://github.com/xenobrain/ruby_vectormath/blob/main/vectormath_2d.rb"

# option 2:
# source code will be downloaded from the specified GitHub username, repository, and file.
# code will be saved locally with a predefined folder convention.
$gtk.download_stb_rb "xenobrain", "ruby_vectormath", "vectormath_2d.rb"

# option 3:
# source code will be downloaded from a direct/raw url and saved to a direct/raw local path.
$gtk.download_stb_rb_raw "https://raw.githubusercontent.com/xenobrain/ruby_vectormath/main/vectormath_2d.rb",
                         "lib/xenobrain/ruby_vectionmath/vectormath_2d.rb"

`reload_history` link

Returns a Hash representing the code files that have be loaded for your game along with timings for the events. This should be used for development/debugging purposes only.

`reload_history_pending` link

Returns a Hash for files that have been queued for reload, but haven't been processed yet. This should be used for development/debugging purposes only.

`reload_if_needed` link

Given a file name, this function will queue the file for reload if it's been modified. An optional second parameter can be passed in to signify if the file should be forced loaded regardless of modified time (true means to force load, false means to load only if the file has been modified). This function should be used for development/debugging purposes only.

State (`args.state`) link

Store your game state inside of this state. Properties with arbitrary nesting is allowed and a backing Entity will be created on your behalf.

def tick args
  args.state.player.x ||= 0
  args.state.player.y ||= 0
end

`entity_id` link

Entities automatically receive an entity_id of type Fixnum.

`entity_type` link

Entities can have an entity_type which is represented as a Symbol.

`created_at` link

Entities have created_at set to Kernel.tick_count when they are created.

`created_at_elapsed` link

Returns the elapsed number of ticks since creation.

`global_created_at` link

Entities have global_created_at set to Kernel.global_tick_count when they are created.

`global_created_at_elapsed` link

Returns the elapsed number of global ticks since creation.

`as_hash` link

Entity cast to a Hash so you can update values as if you were updating a Hash.

`new_entity` link

Creates a new Entity with a type, and initial properties. An option block can be passed to change the newly created entity:

def tick args
  args.state.player ||= args.state.new_entity :player, x: 0, y: 0 do |e|
    e.max_hp = 100
    e.hp     = e.max_hp * rand
  end
end

`new_entity_strict` link

Creates a new Strict Entity. While Entities created via args.state.new_entity can have new properties added later on, Entities created using args.state.new_entity_strict must define all properties that are allowed during its initialization. Attempting to add new properties after initialization will result in an exception.

`tick_count` link

Returns the current tick of the game. Kernel.tick_count is 0 when the game is first started or if the game is reset via $gtk.reset.

Geometry (`args.geometry`) link

The Geometry module contains methods for calculations that are frequently used in game development.

The following functions of Geometry are mixed into Hash, Array, and DragonRuby's Entity class:

intersect_rect?
inside_rect?
scale_rect
angle_to
angle_from
point_inside_circle?
center_inside_rect
center_inside_rect_x
center_inside_rect_y
anchor_rect
rect_center_point

You can invoke the functions above using either the mixin variant or the module variant. Example:

def tick args
  # define to rectangles
  rect_1 = { x: 0, y: 0, w: 100, h: 100 }
  rect_2 = { x: 50, y: 50, w: 100, h: 100 }

  # mixin variant
  # call geometry method function from instance of a Hash class
  puts rect_1.intersect_rect?(rect_2)

  # OR

  # module variants
  puts args.geometry.intersect_rect?(rect_1, rect_2)
  puts Geometry.intersect_rect?(rect_1, rect_2)
end

`intersect_rect?` link

Invocation variants:

instance.intersect_rect?(other, tolerance)
args.geometry.intersect_rect?(rect_1, rect_2, tolerance)
Geometry.intersect_rect?(rect_1, rect_2, tolerance)
args.inputs.mouse.intersect_rect?(other, tolerance)

Given two rectangle primitives this function will return true or false depending on if the two rectangles intersect or not. An optional final parameter can be passed in representing the tolerance of overlap needed to be considered a true intersection. The default value of tolerance is 0.1 which keeps the function from returning true if only the edges of the rectangles overlap.

?> :anchor_x, and anchor_y is taken into consideration if the objects respond to these methods.

Here is an example where one rectangle is stationary, and another rectangle is controlled using directional input. The rectangles change color from blue to read if they intersect.

def tick args
  # define a rectangle in state and position it
  # at the center of the screen with a color of blue
  args.state.box_1 ||= {
    x: 640 - 20,
    y: 360 - 20,
    w: 40,
    h: 40,
    r: 0,
    g: 0,
    b: 255
  }

  # create another rectangle in state and position it
  # at the far left center
  args.state.box_2 ||= {
    x: 0,
    y: 360 - 20,
    w: 40,
    h: 40,
    r: 0,
    g: 0,
    b: 255
  }

  # take the directional input and use that to move the second rectangle around
  # increase or decrease the x value based on if left or right is held
  args.state.box_2.x += args.inputs.left_right * 5
  # increase or decrease the y value based on if up or down is held
  args.state.box_2.y += args.inputs.up_down * 5

  # change the colors of the rectangles based on whether they
  # intersect or not
  if args.state.box_1.intersect_rect? args.state.box_2
    args.state.box_1.r = 255
    args.state.box_1.g = 0
    args.state.box_1.b = 0

    args.state.box_2.r = 255
    args.state.box_2.g = 0
    args.state.box_2.b = 0
  else
    args.state.box_1.r = 0
    args.state.box_1.g = 0
    args.state.box_1.b = 255

    args.state.box_2.r = 0
    args.state.box_2.g = 0
    args.state.box_2.b = 255
  end

  # render the rectangles as border primitives on the screen
  args.outputs.borders << args.state.box_1
  args.outputs.borders << args.state.box_2
end

`inside_rect?` link

Invocation variants:

instance.inside_rect?(other)
args.geometry.inside_rect?(rect_1, rect_2)
Geometry.inside_rect?(rect_1, rect_2)

Given two rectangle primitives this function will return true or false depending on if the first rectangle (or self) is inside of the second rectangle.

Here is an example where one rectangle is stationary, and another rectangle is controlled using directional input. The rectangles change color from blue to read if the movable rectangle is entirely inside the stationary rectangle.

?> :anchor_x, and anchor_y is taken into consideration if the objects respond to these methods.

def tick args
  # define a rectangle in state and position it
  # at the center of the screen with a color of blue
  args.state.box_1 ||= {
    x: 640 - 40,
    y: 360 - 40,
    w: 80,
    h: 80,
    r: 0,
    g: 0,
    b: 255
  }

  # create another rectangle in state and position it
  # at the far left center
  args.state.box_2 ||= {
    x: 0,
    y: 360 - 10,
    w: 20,
    h: 20,
    r: 0,
    g: 0,
    b: 255
  }

  # take the directional input and use that to move the second rectangle around
  # increase or decrease the x value based on if left or right is held
  args.state.box_2.x += args.inputs.left_right * 5
  # increase or decrease the y value based on if up or down is held
  args.state.box_2.y += args.inputs.up_down * 5

  # change the colors of the rectangles based on whether they
  # intersect or not
  if args.state.box_2.inside_rect? args.state.box_1
    args.state.box_1.r = 255
    args.state.box_1.g = 0
    args.state.box_1.b = 0

    args.state.box_2.r = 255
    args.state.box_2.g = 0
    args.state.box_2.b = 0
  else
    args.state.box_1.r = 0
    args.state.box_1.g = 0
    args.state.box_1.b = 255

    args.state.box_2.r = 0
    args.state.box_2.g = 0
    args.state.box_2.b = 255
  end

  # render the rectangles as border primitives on the screen
  args.outputs.borders << args.state.box_1
  args.outputs.borders << args.state.box_2
end

`scale_rect` link

Given a Rectangle this function returns a new rectangle with a scaled size.

ratio: the ratio by which to scale the rect. A ratio of 2 will double the dimensions of the rect while a ratio of 0.5 will halve its dimensions.
anchor_x and anchor_y specify the point within the rect from which to resize it. Setting both to 0 will affect the width and height of the rect, leaving x and y unchanged. Setting both to 0.5 will scale all sides of the rect proportionally from the center.

def tick args
  # a rect at the center of the screen
  args.state.rect_1 ||= { x: 640 - 20, y: 360 - 20, w: 40, h: 40 }

  # render the rect
  args.outputs.borders << args.state.rect_1

  # the rect half the size with the x and y position unchanged
  args.outputs.borders << args.state.rect_1.scale_rect(0.5)

  # the rect double the size, repositioned in the center given anchor optional arguments
  args.outputs.borders << args.state.rect_1.scale_rect(2, 0.5, 0.5)
end

`scale_rect_extended` link

The behavior is similar to scale_rect except that you can independently control the scale of each axis. The parameters are all named:

percentage_x: percentage to change the width (default value of 1.0)
percentage_y: percentage to change the height (default value of 1.0)
anchor_x: anchor repositioning of x (default value of 0.0)
anchor_y: anchor repositioning of y (default value of 0.0)

def tick args
  baseline_rect = { x: 640 - 20, y: 360 - 20, w: 40, h: 40 }
  args.state.rect_1 ||= baseline_rect
  args.state.rect_2 ||= baseline_rect.scale_rect_extended(percentage_x: 2,
                                                          percentage_y: 0.5,
                                                          anchor_x: 0.5,
                                                          anchor_y: 1.0)
  args.outputs.borders << args.state.rect_1
  args.outputs.borders << args.state.rect_2
end

`anchor_rect` link

Returns a new rect that is anchored by an anchor_x and anchor_y value. The width and height of the rectangle is taken into consideration when determining the anchor position:

def tick args
  args.state.rect ||= {
    x: 640,
    y: 360,
    w: 100,
    h: 100
  }

  # rect's center: 640 + 50, 360 + 50
  args.outputs.borders << args.state.rect.anchor_rect(0, 0)

  # rect's center: 640, 360
  args.outputs.borders << args.state.rect.anchor_rect(0.5, 0.5)

  # rect's center: 640, 360
  args.outputs.borders << args.state.rect.anchor_rect(0.5, 0)
end

`angle` link

Invocation variants:

args.geometry.angle start_point, end_point
Geometry.angle start_point, end_point

Returns an angle in degrees from the start_point to the end_point (if you want the value in radians call .to_radians on the value returned).

`angle_from` link

Invocation variants:

args.geometry.angle_from start_point, end_point
Geometry.angle_from start_point, end_point
start_point.angle_from end_point

Returns an angle in degrees from the end_point to the start_point (if you want the value in radians, you can call .to_radians on the value returned):

def tick args
  rect_1 ||= {
    x: 0,
    y: 0,
  }

  rect_2 ||= {
    x: 100,
    y: 100,
  }

  angle = rect_1.angle_from rect_2 # returns 225 degrees
  angle_radians = angle.to_radians
  args.outputs.labels << { x: 30, y: 30.from_top, text: "#{angle}, #{angle_radians}" }

  angle = args.geometry.angle_from rect_1, rect_2 # returns 225 degrees
  angle_radians = angle.to_radians
  args.outputs.labels << { x: 30, y: 60.from_top, text: "#{angle}, #{angle_radians}" }
end

`angle_to`, `angle` link

Invocation variants:

args.geometry.angle_to start_point, end_point
args.geometry.angle start_point, end_point (alias)
Geometry.angle_to start_point, end_point
Geometry.angle start_point, end_point (alias)
start_point.angle_to end_point

Returns an angle in degrees to the end_point from the start_point (if you want the value in radians, you can call .to_radians on the value returned):

def tick args
  rect_1 ||= {
    x: 0,
    y: 0,
  }

  rect_2 ||= {
    x: 100,
    y: 100,
  }

  angle = rect_1.angle_to rect_2 # returns 45 degrees
  angle_radians = angle.to_radians
  args.outputs.labels << { x: 30, y: 30.from_top, text: "#{angle}, #{angle_radians}" }

  angle = args.geometry.angle_to rect_1, rect_2 # returns 45 degrees
  angle_radians = angle.to_radians
  args.outputs.labels << { x: 30, y: 60.from_top, text: "#{angle}, #{angle_radians}" }
end

`angle_turn_direction` link

Invocation variants:

args.geometry.angle_turn_direction angle, target_angle
Geometry.angle_turn_direction angle, target_angle

Returns 1 or -1 depending on which direction the angle needs to turn to reach the target_angle most efficiently. The angles are assumed to be in degrees. 1 means turn clockwise, and -1 means turn counter-clockwise.

`distance` link

Returns the distance between two points;

def tick args
  rect_1 ||= {
    x: 0,
    y: 0,
  }

  rect_2 ||= {
    x: 100,
    y: 100,
  }

  distance = args.geometry.distance rect_1, rect_2
  args.outputs.labels << {
    x: 30,
    y: 30.from_top,
    text: "#{distance}"
  }

  args.outputs.lines << {
    x: rect_1.x,
    y: rect_1.y,
    x2: rect_2.x,
    y2: rect_2.y
  }
end

`point_inside_circle?` link

Invocation variants:

point_1.point_inside_circle? circle_center, circle_radius
args.geometry.point_inside_circle? point_1, circle_center, circle_radius
Geometry.point_inside_circle? point_1, circle_center, circle_radius

circle_center can also contain the radius value (instead of passing it as a separate argument).

Returns true if a point is inside of a circle defined as a center point and radius.

def tick args
  # define circle center
  args.state.circle_center ||= {
    x: 640,
    y: 360
  }

  # define circle radius
  args.state.circle_radius ||= 100

  # define point
  args.state.point_1 ||= {
    x: 100,
    y: 100
  }

  # allow point to be moved using keyboard
  args.state.point_1.x += args.inputs.left_right * 5
  args.state.point_1.y += args.inputs.up_down * 5

  # determine if point is inside of circle
  intersection = args.geometry.point_inside_circle? args.state.point_1,
                                                    args.state.circle_center,
                                                    args.state.circle_radius

  # render point as a square
  args.outputs.sprites << {
    x: args.state.point_1.x - 20,
    y: args.state.point_1.y - 20,
    w: 40,
    h: 40,
    path: "sprites/square/blue.png"
  }

  # if there is an intersection, render a red circle
  # otherwise render a blue circle
  if intersection
    args.outputs.sprites << {
      x: args.state.circle_center.x - args.state.circle_radius,
      y: args.state.circle_center.y - args.state.circle_radius,
      w: args.state.circle_radius * 2,
      h: args.state.circle_radius * 2,
      path: "sprites/circle/red.png",
      a: 128
    }
  else
    args.outputs.sprites << {
      x: args.state.circle_center.x - args.state.circle_radius,
      y: args.state.circle_center.y - args.state.circle_radius,
      w: args.state.circle_radius * 2,
      h: args.state.circle_radius * 2,
      path: "sprites/circle/blue.png",
      a: 128
    }
  end
end

`center_inside_rect` link

Invocation variants:

target_rect.center_inside_rect reference_rect
args.geometry.center_inside_rect target_rect, reference_rect
Geometry.center_inside_rect target_rect, reference_rect

Given a target rect and a reference rect, the target rect is centered inside the reference rect (a new rect is returned).

def tick args
  rect_1 = {
    x: 0,
    y: 0,
    w: 100,
    h: 100
  }

  rect_2 = {
    x: 640 - 100,
    y: 360 - 100,
    w: 200,
    h: 200
  }

  centered_rect = args.geometry.center_inside_rect rect_1, rect_2
  # OR
  # centered_rect = rect_1.center_inside_rect rect_2

  args.outputs.solids << rect_1.merge(r: 255)
  args.outputs.solids << rect_2.merge(b: 255)
  args.outputs.solids << centered_rect.merge(g: 255)
end

`ray_test` link

Given a point and a line, ray_test returns one of the following symbols based on the location of the point relative to the line: :left, :right, :on

def tick args
  # create a point based off of the mouse location
  point = {
    x: args.inputs.mouse.x,
    y: args.inputs.mouse.y
  }

  # draw a line from the bottom left to the top right
  line = {
    x: 0,
    y: 0,
    x2: 1280,
    y2: 720
  }

  # perform ray_test on point and line
  ray = args.geometry.ray_test point, line

  # output the results of ray test at mouse location
  args.outputs.labels << {
    x: point.x,
    y: point.y + 25,
    text: "#{ray}",
    alignment_enum: 1,
    vertical_alignment_enum: 1,
  }

  # render line
  args.outputs.lines << line

  # render point
  args.outputs.solids << {
    x: point.x - 5,
    y: point.y - 5,
    w: 10,
    h: 10
  }
end

`line_rise_run` link

Given a line, this function returns a Hash with x and y keys representing a normalized representation of the rise and run of the line.

def tick args
  # draw a line from the bottom left to the top right
  line = {
    x: 0,
    y: 0,
    x2: 1280,
    y2: 720
  }

  # get rise and run of line
  rise_run = args.geometry.line_rise_run line

  # output the rise and run of line
  args.outputs.labels << {
    x: 640,
    y: 360,
    text: "#{rise_run}",
    alignment_enum: 1,
    vertical_alignment_enum: 1,
  }

  # render the line
  args.outputs.lines << line
end

`line_intersect` link

Given two lines (:x, :y, :x2, :y2), this function returns point of intersection if the line segments intersect. If the line segments do not intersect, nil is returned. If you want the lines to be treated as infinite lines, use ray_intersect.

Invocation variants:

args.geometry.line_intersect line_1, line_2
Geometry.line_intersect line_1, line_2

def tick args
  args.state.line_one ||= { x: 0, y: 0, x2: 1280, y2: 720 }
  line_two = { x: 0, y: 720, x2: args.inputs.mouse.x, y2: args.inputs.mouse.y }
  args.state.intersect_point = args.geometry.line_intersect args.state.line_one, line_two
  args.outputs.lines << { x: 0, y: 0, x2: 1280, y2: 720 }
  args.outputs.lines << line_two
  if args.state.intersect_point
    args.outputs.solids << {
      x: args.state.intersect_point.x,
      y: args.state.intersect_point.y,
      w: 10,
      h: 10,
      anchor_x: 0.5,
      anchor_y: 0.5,
      r: 255,
      g: 0,
      b: 0
    }
  end
end

`ray_intersect` link

Given two lines (:x, :y, :x2, :y2), this function returns point of intersection if the ray (infinite line) intersect. If the lines are parallel, nil is returned. If you do not want the lines to be treated as infinite lines, use line_intersect.

Invocation variants:

args.geometry.ray_intersect line_1, line_2
Geometry.ray_intersect line_1, line_2

def tick args
  # define line_one to go from the bottom left to the top right
  args.state.line_one ||= { x: 0, y: 0, x2: 1280, y2: 720 }

  # have the mouse control the x2 and y2 of line_two
  line_two = { x: 0, y: 720, x2: args.inputs.mouse.x, y2: args.inputs.mouse.y }

  # calc if line_one and line_two intersect and if so, the point of intersection
  args.state.intersect_point = args.geometry.ray_intersect args.state.line_one, line_two

  # draw line_one
  args.outputs.lines << { x: 0, y: 0, x2: 1280, y2: 720 }

  # draw line_two
  args.outputs.lines << line_two

  # draw a rect at the intersection point
  if args.state.intersect_point
    args.outputs.solids << {
      x: args.state.intersect_point.x,
      y: args.state.intersect_point.y,
      w: 10,
      h: 10,
      anchor_x: 0.5,
      anchor_y: 0.5,
      r: 255,
      g: 0,
      b: 0 }
  end
end

`rotate_point` link

Given a point and an angle in degrees, a new point is returned that is rotated around the origin by the degrees amount. An optional third argument can be provided to rotate the angle around a point other than the origin.

def tick args
  args.state.rotate_amount ||= 0
  args.state.rotate_amount  += 1

  if args.state.rotate_amount >= 360
    args.state.rotate_amount = 0
  end

  point_1 = {
    x: 100,
    y: 100
  }

  # rotate point around 0, 0
  rotated_point_1 = args.geometry.rotate_point point_1,
                                               args.state.rotate_amount

  args.outputs.solids << {
    x: rotated_point_1.x - 5,
    y: rotated_point_1.y - 5,
    w: 10,
    h: 10
  }

  point_2 = {
    x: 640 + 100,
    y: 360 + 100
  }

  # rotate point around center screen
  rotated_point_2 = args.geometry.rotate_point point_2,
                                               args.state.rotate_amount,
                                               x: 640, y: 360

  args.outputs.solids << {
    x: rotated_point_2.x - 5,
    y: rotated_point_2.y - 5,
    w: 10,
    h: 10
  }
end

`find_intersect_rect` link

Given a rect and a collection of rects, find_intersect_rect returns the first rect that intersects with the the first parameter.

:anchor_x, and anchor_y is taken into consideration if the objects respond to these methods.

If you find yourself doing this:

collision = args.state.terrain.find { |t| t.intersect_rect? args.state.player }

Consider using find_intersect_rect instead (it's more descriptive and faster):

collision = args.geometry.find_intersect_rect args.state.player, args.state.terrain

?> Function returns nil if either parameter is nil (nil values within the collection are skipped).

`find_all_intersect_rect` link

Given a rect and a collection of rects, find_all_intersect_rect returns all rects that intersects with the the first parameter.

:anchor_x, and anchor_y is taken into consideration if the objects respond to these methods.

If you find yourself doing this:

collisions = args.state.terrain.find_all { |t| t.intersect_rect? args.state.player }

Consider using find_all_intersect_rect instead (it's more descriptive and faster):

collisions = args.geometry.find_all_intersect_rect args.state.player, args.state.terrain

?> Function returns an empty Array if either parameter is nil (nil values within the collection are skipped).

`find_intersect_rect_quad_tree` link

This is a faster collision algorithm for determining if a rectangle intersects any rectangle in an array. In order to use find_intersect_rect_quad_tree, you must first generate a quad tree data structure using create_quad_tree. Use this function if find_intersect_rect isn't fast enough.

def tick args
  # create a player
  args.state.player ||= {
    x: 640 - 10,
    y: 360 - 10,
    w: 20,
    h: 20
  }

  # allow control of player movement using arrow keys
  args.state.player.x += args.inputs.left_right * 5
  args.state.player.y += args.inputs.up_down * 5

  # generate 40 random rectangles
  args.state.boxes ||= 40.map do
    {
      x: 1180 * rand + 50,
      y: 620 * rand + 50,
      w: 100,
      h: 100
    }
  end

  # generate a quad tree based off of rectangles.
  # the quad tree should only be generated once for
  # a given array of rectangles. if the rectangles
  # change, then the quad tree must be regenerated
  args.state.quad_tree ||= args.geometry.quad_tree_create args.state.boxes

  # use quad tree and find_intersect_rect_quad_tree to determine collision with player
  collision = args.geometry.find_intersect_rect_quad_tree args.state.player,
                                                          args.state.quad_tree

  # if there is a collision render a red box
  if collision
    args.outputs.solids << collision.merge(r: 255)
  end

  # render player as green
  args.outputs.solids << args.state.player.merge(g: 255)

  # render boxes as borders
  args.outputs.borders << args.state.boxes
end

`find_all_intersect_rect_quad_tree` link

This is a faster collision algorithm for determining if a rectangle intersects other rectangles in an array. In order to use find_all_intersect_rect_quad_tree, you must first generate a quad tree data structure using create_quad_tree. Use this function if find_all_intersect_rect isn't fast enough.

def tick args
  # create a player
  args.state.player ||= {
    x: 640 - 10,
    y: 360 - 10,
    w: 20,
    h: 20
  }

  # allow control of player movement using arrow keys
  args.state.player.x += args.inputs.left_right * 5
  args.state.player.y += args.inputs.up_down * 5

  # generate 40 random rectangles
  args.state.boxes ||= 40.map do
    {
      x: 1180 * rand + 50,
      y: 620 * rand + 50,
      w: 100,
      h: 100
    }
  end

  # generate a quad tree based off of rectangles.
  # the quad tree should only be generated once for
  # a given array of rectangles. if the rectangles
  # change, then the quad tree must be regenerated
  args.state.quad_tree ||= args.geometry.quad_tree_create args.state.boxes

  # use quad tree and find_intersect_rect_quad_tree to determine collision with player
  collisions = args.geometry.find_all_intersect_rect_quad_tree args.state.player,
                                                              args.state.quad_tree

  # if there is a collision render a red box
  args.outputs.solids << collisions.map { |c| c.merge(r: 255) }

  # render player as green
  args.outputs.solids << args.state.player.merge(g: 255)

  # render boxes as borders
  args.outputs.borders << args.state.boxes
end

`line_angle` link

Given a line, this function will return the angle of the line in degrees.

`vec2_dot_product` link

Given two Hashes with x and y keys (or Objects that respond to x and y), this function will return the dot product of the two vectors.