Welcome to Simple 2D!

Simple 2D is a small, open-source graphics engine providing essential 2D drawing, media, and input capabilities. It's written in C and works across many platforms, creating native windows and interacting with hardware using SDL while rendering content with OpenGL.

Please note this README will be continuously updated as new features are added, bugs are fixed, and other changes are made. View the release notes for a link to that version's documentation.

Open an issue on GitHub if you encounter any problems, have a feature request, or simply want to ask a question. Learn more about contributing below.

Contents

• Getting started
  • ...on macOS
    • iOS and tvOS
  • ...on Windows
  • ...on Linux
    • Linux/ARM platforms
  • The command-line utility
• Building from source
• Tests
• Creating apps with Simple 2D
  • 2D basics
    • The window
    • Update and render
  • Drawing
    • Shapes
    • Images
    • Sprites
    • Text
  • Audio
    • Sounds
    • Music
  • Input
    • Keyboard
    • Mouse
    • Game controllers
• Contributing
• About the project

---

Getting started

Simple 2D supports all major operating systems and hardware platforms, and is tested on the latest releases of macOS, iOS, tvOS, Windows, Linux, and Raspbian on the Raspberry Pi.

To install the latest release...

...on macOS

Use Homebrew:

brew tap simple2d/tap
brew install simple2d

iOS and tvOS

The Homebrew formula above will also install the iOS and tvOS frameworks to /usr/local/Frameworks/Simple2D by default. After installing, run the simple2d simulator command to see available options for interacting with the iOS and tvOS simulators. Run simple2d build to learn how to build Xcode projects with the iOS and tvOS SDKs. Example Xcode projects can be found in the deps repository.

...on Windows

Download the Windows installer for Visual C++ or MinGW.

For MinGW, we recommend using an MSYS2 environment (also available on Chocolatey) along with a MinGW 64-bit command prompt (usually mingw64.exe). Simple 2D can also be installed on MinGW using the Linux instructions below.

...on Linux

Run the simple2d.sh Bash script. Everything will be explained along the way and you'll be prompted before any action is taken. To run the script from the web, paste this snippet in your terminal:

url='https://raw.githubusercontent.com/simple2d/simple2d/master/bin/simple2d.sh'; which curl > /dev/null && cmd='curl -fsSL' || cmd='wget -qO -'; bash <($cmd $url) install

Linux/ARM platforms

Simple 2D supports ARM platforms running Linux, like the Raspberry Pi. Since most Linux distributions have SDL packages configured for traditional desktop platforms, the install script will compile SDL from source when ARM is detected, disabling windowing systems (like X11) and OpenGL (forcing OpenGL ES instead).

The command-line utility

Once installed, use the simple2d command-line utility to update Simple 2D, check for issues, output the libraries needed to compile applications, and more. Simply run simple2d to see all available commands and options.

Building from source

Alternatively, you can compile and install Simple 2D from source. First clone this repo using:

git clone --recursive https://github.com/simple2d/simple2d.git

To keep the size of this repository small, Git submodules are used to reference test media and dependencies. The --recursive flag ensures submodules are initialize and updated when this repo is cloned. If you happened to clone this repo without the --recursive flag, you can still initialize and update submodules with:

git submodule init
git submodule update --remote

Update these submodules at any time using git submodule update --remote

Next, build and install on Unix-like systems, including Windows using MinGW, by running:

make && make install

On Windows using Visual C++, open a 64-bit Visual Studio command prompt and run:

nmake /f NMakefile all install

Note that on macOS and Linux, the makefile will not check for or install dependencies, unlike installing via Homebrew or the simple2d.sh script, respectively. Dependencies for Windows, supporting both Visual C++ and MinGW, are included in this repo (referenced by the deps submodule) and installed by both makefiles.

On Windows using Visual C++, Simple 2D will be installed to %LOCALAPPDATA%\simple2d, so make sure to add that to your path (for example with set PATH=%PATH%;%LOCALAPPDATA%\simple2d). In all other cases, it will be installed to /usr/local/. On Windows using MinGW, make sure /usr/local/bin is in your path as well.

Building release archives

To build the release archives, which are attached as downloads with each release, run make release on macOS and Windows using MinGW, and nmake /f NMakefile release on Windows using Visual C++.

Tests

Simple 2D has several test programs to make sure everything is working as it should.

• auto.c — A set of automated unit tests for the public interface.
• triangle.c — The "Hello Triangle" example in this README.
• testcard.c — A graphical card, similar to TV test cards, with the goal of ensuring visuals and inputs are working properly.
• audio.c — Tests audio functions with various file formats interpreted as both sound samples and music.
• controller.c — Provides visual and numeric feedback of game controller input.
• triangle-ios-tvos.c — A modified triangle.c designed for iOS and tvOS devices.

Building and running tests

Run make test, or nmake /f NMakefile test on Windows using Visual C++, to compile tests to the test/ directory. The resulting executables will have the same name as their C source files. Since media paths are set relatively in these test programs, make sure to cd into the test/ directory before running a test, for example:

# On Unix-like systems
make test && cd test/ && ./testcard

# On Windows using MinGW
make test & cd test\ & testcard.exe

# On Windows using Visual C++
nmake /f NMakefile test & cd test\ & testcard.exe

Each test also has a makefile target, so you can build and run tests using, for example, make test testcard. Or, conveniently uninstall everything, rebuild Simple 2D and tests from source, and run tests using make rebuild <name_of_test>, for example:

# Rebuild and run `auto.c` then `testcard.c`...

# ...on Unix-like systems and Windows using MinGW
make rebuild auto testcard

# ...on Windows using Visual C++
nmake /f NMakefile rebuild auto testcard

iOS and tvOS tests

To run the iOS and tvOS tests, first run make frameworks && make install-frameworks to build and install the iOS and tvOS frameworks. Next, run make ios to run the test in an iOS simulator and make tvos to run in a tvOS Simulator.

---

Creating apps with Simple 2D

Making 2D apps is simple! Let's create a window and draw a triangle...

#include <simple2d.h>

void render() {
  S2D_DrawTriangle(
    320,  50, 1, 0, 0, 1,
    540, 430, 0, 1, 0, 1,
    100, 430, 0, 0, 1, 1
  );
}

int main() {

  S2D_Window *window = S2D_CreateWindow(
    "Hello Triangle", 640, 480, NULL, render, 0
  );

  S2D_Show(window);
  return 0;
}

Save the code above to a file called triangle.c and compile it by running simple2d build triangle.c on the command line (in MinGW, run this in a Bash prompt). Now run the app using ./triangle on macOS and Linux, or triangle.exe on Windows, and enjoy your stunning triangle in a 640x480 window at 60 frames per second!

The simple2d build command is a helpful shortcut for compiling a single source file. Of course, you can also use a compiler directly, for example on Unix-like systems:

cc triangle.c `simple2d --libs` -o triangle

And on Windows using Visual C++ in a developer command prompt:

cl triangle.c /I %LOCALAPPDATA%\simple2d /link /LIBPATH %LOCALAPPDATA%\simple2d\simple2d.lib /SUBSYSTEM:CONSOLE

# as a PowerShell command
iex "cl triangle.c $(simple2d --libs)"

2D basics

Let's learn about structuring applications for 2D drawing and more.

The window

All rendered content, input, and sound is controlled by the window, so creating a window is the first thing you'll do. Start by declaring a pointer to a S2D_Window structure and initialize it using S2D_CreateWindow().

S2D_Window *window = S2D_CreateWindow(
  "Hello World!",  // title of the window
  800, 600,        // width and height
  update, render,  // callback function pointers (these can be NULL)
  0                // flags
);

To set the window's width and height the same as the display's, use S2D_DISPLAY_WIDTH and S2D_DISPLAY_HEIGHT for those values, respectively.

The window flags can be 0 or any one of the following:

S2D_RESIZABLE   // allow window to be resized
S2D_BORDERLESS  // show window without a border
S2D_FULLSCREEN  // show window at fullscreen
S2D_HIGHDPI     // enable high DPI mode

Flags can also be combined using the bitwise OR operator, for example: S2D_RESIZABLE | S2D_BORDERLESS

The size of the viewport, the area where graphics are drawn in the window, can be set independently of the window size like so:

window->viewport.width  = 400;
window->viewport.height = 300;

The viewport has various scaling modes, such as S2D_FIXED (viewport stays the same size as the window size changes), S2D_EXPAND (viewport expands to fill the window when resized), S2D_SCALE (the default, where the viewport scales proportionately and is centered in the window), or S2D_STRETCH (viewport stretches to fill the entire window). Set the mode like this:

window->viewport.mode = S2D_FIXED;

Before showing the window, these attributes can be set:

window->vsync = false;     // set the vertical sync, true by default
window->icon = "app.png";  // set the icon for the window

Once your window is ready to go, show it using:

S2D_Show(window);

Any time before or during the window is being shown, these attributes can be set:

// Cap the frame rate, 60 frames per second by default
window->fps_cap = 30;

// Set the window background color, black by default
window->background.r = 1.0;
window->background.g = 0.5;
window->background.b = 0.8;
window->background.a = 1.0;

Callback functions can also be changed any time — more on that below. Many values can be read from the S2D_Window structure, see the simple2d.h header file for details.

The window icon can be changed using:

S2D_SetIcon(window, "new_icon.png");

Take a screenshot of the window in PNG format, providing a file path:

S2D_Screenshot(window, "./screenshot.png");

When you're done with the window, free it using:

S2D_FreeWindow(window);

Update and render

The window loop is where all the action takes place: the frame rate is set, input is handled, the app state is updated, and visuals are rendered. You'll want to declare two essential functions which will be called by the window loop: update() and render(). Like a traditional game loop, update() is used for updating the application state, and render() is used for drawing the scene. Simple 2D optimizes both functions for performance and accuracy, so it's good practice to keep those updating and rendering tasks separate.

The update and render functions should look like this:

void update() { /* update your application state */ }
void render() { /* draw stuff */ }

Remember to add these function names when calling S2D_CreateWindow() (see "The window" section above for an example).

To exit the window loop at any time, use:

S2D_Close(window);

Drawing

All kinds of shapes and textures can be drawn in the window. Learn about each of them below.

Shapes

Several geometric shapes are available, like triangles, quadrilaterals (which rectangles and squares can be made from), lines, and circles. Every shape contains vertices, that is, places where two lines meet to form an angle (a triangle has three, for example). For each vertex of a triangle and quadrilateral, there are six values which need to be set: the x and y coordinates, and four color values. Lines have two vertices, although colors for each corner can be set. Circles have a single center point and color that can be set. When vertices have different color values, the space between them are blended in a gradient.

The shorthand for the examples below are:

x = the x coordinate
y = the y coordinate

// Color range is from 0.0 to 1.0
r = red
g = green
b = blue
a = alpha (opacity)

Using this notation, x2 would be the second x coordinate, and b2 would be the blue value at that vertex.

To draw a triangle, use:

S2D_DrawTriangle(x1, y1, r1, g1, b1, a1,
                 x2, y2, r2, g2, b2, a2,
                 x3, y3, r3, g3, b3, a3);

To draw a quadrilateral, use:

S2D_DrawQuad(x1, y1, r1, g1, b1, a1,
             x2, y2, r2, g2, b2, a2,
             x3, y3, r3, g3, b3, a3,
             x4, y4, r4, g4, b4, a4);

To draw a line, use:

S2D_DrawLine(x1, y1, x2, y2,
             width,
             r1, g1, b1, a1,
             r2, g2, b2, a2,
             r3, g3, b3, a3,
             r4, g4, b4, a4);

To draw a circle, use:

S2D_DrawCircle(x, y, radius, sectors, r, g, b, a);

Images

Images in many popular formats, like JPEG, PNG, and BMP can be drawn in the window. Unlike shapes, images need to be read from files and stored in memory. Simply declare a pointer to an S2D_Image structure and initialize it using S2D_CreateImage() providing the file path to the image.

S2D_Image *img = S2D_CreateImage("image.png");

If the image can't be found, it will return NULL.

Once you have your image, you can then change its x, y position like so:

img->x = 125;
img->y = 350;

Change the size of the image by adjusting its width and height:

img->width  = 256;
img->height = 512;

Rotate the image like so:

// Angle should be in degrees
// The last parameter is the point the image should rotate around, either:
//   S2D_CENTER, S2D_TOP_LEFT, S2D_TOP_RIGHT, S2D_BOTTOM_LEFT, or S2D_BOTTOM_RIGHT
S2D_RotateImage(img, angle, S2D_CENTER);

// Or, set a custom point to rotate around
img->rx = 50;
img->ry = 75;

// Set the rotation angle directly
img->rotate = 90;

You can also adjust the color of the image like this:

// Default is 1.0 for each, a white color filter
img->color.r = 1.0;
img->color.g = 0.8;
img->color.b = 0.2;
img->color.a = 1.0;

Finally, draw the image using:

S2D_DrawImage(img);

Since images are allocated dynamically, free them using:

S2D_FreeImage(img);

Sprites

Sprites are special kinds of images which can be used to create animations. To create a sprite, declare a pointer to an S2D_Sprite structure and initialize it using S2D_CreateSprite() providing the file path to the sprite sheet image.

S2D_Sprite *spr = S2D_CreateSprite("sprite_sheet.png");

If the sprite image can't be found, it will return NULL.

Clip the sprite sheet to a single image by providing a clipping rectangle:

S2D_ClipSprite(spr, x, y, width, height);

The x, y position of the sprite itself can be changed like so:

spr->x = 150;
spr->y = 275;

Change the size of the sprite by adjusting its width and height:

spr->width  = 100;
spr->height = 100;

Rotate the sprite like so:

// Angle should be in degrees
// The last parameter is the point the sprite should rotate around, either:
//   S2D_CENTER, S2D_TOP_LEFT, S2D_TOP_RIGHT, S2D_BOTTOM_LEFT, or S2D_BOTTOM_RIGHT
S2D_RotateSprite(spr, angle, S2D_CENTER);

// Or, set a custom point to rotate around
spr->rx = 50;
spr->ry = 75;

// Set the rotation angle directly
spr->rotate = 90;

You can also adjust the color of the sprite image like this:

// Default is 1.0 for each, a white color filter
spr->color.r = 1.0;
spr->color.g = 0.8;
spr->color.b = 0.2;
spr->color.a = 1.0;

Finally, draw the sprite using:

S2D_DrawSprite(spr);

Since sprites are allocated dynamically, free them using:

S2D_FreeSprite(spr);

Text

Text is drawn much like images. Start by finding your favorite OpenType font (with a .ttf or .otf file extension), then declare a pointer to a S2D_Text structure and initialize it using S2D_CreateText() providing the file path to the font, the message to display, and the size.

S2D_Text *txt = S2D_CreateText("vera.ttf", "Hello world!", 20);

If the font file can't be found, it will return NULL.

You can then change the x, y position of the text, for example:

txt->x = 127;
txt->y = 740;

Rotate the text like so:

// Angle should be in degrees
// The last parameter is the point the text should rotate around, either:
//   S2D_CENTER, S2D_TOP_LEFT, S2D_TOP_RIGHT, S2D_BOTTOM_LEFT, or S2D_BOTTOM_RIGHT
S2D_RotateText(txt, angle, S2D_CENTER);

// Or, set a custom point to rotate around
txt->rx = 50;
txt->ry = 75;

// Set the rotation angle directly
txt->rotate = 90;

Change the color of the text like this:

// Default is 1.0 for each, a white color filter
txt->color.r = 0.5;
txt->color.g = 1.0;
txt->color.b = 0.0;
txt->color.a = 0.7;

Finally, draw the text using:

S2D_DrawText(txt);

You can also change the text message at any time:

S2D_SetText(txt, "A different message!");

// Format text just like `printf`
S2D_SetText(txt, "Welcome %s!", player);

Since text is allocated dynamically, free them using:

S2D_FreeText(txt);

Audio

Simple 2D supports a number of popular audio formats, including WAV, MP3, Ogg Vorbis, and FLAC. There are two kinds of audio concepts: sounds and music. Sounds are intended to be short samples, played without interruption, like an effect. Music is for longer pieces which can be played, paused, stopped, resumed, and faded out, like a background soundtrack.

Sounds

Create a sound by first declaring a pointer to a S2D_Sound structure and initialize it using S2D_CreateSound() providing the path to the audio file.

S2D_Sound *snd = S2D_CreateSound("sound.wav");

If the audio file can't be found, it will return NULL.

Play the sound like this:

S2D_PlaySound(snd);

Since sounds are allocated dynamically, free them using:

S2D_FreeSound(snd);

Music

Similarly, create some music by declaring a pointer to a S2D_Music structure and initialize it using S2D_CreateMusic() providing the path to the audio file.

S2D_Music *mus = S2D_CreateMusic("music.ogg");

If the audio file can't be found, it will return NULL.

Play the music like this, where the second parameter is a boolean value indicating whether the music should be repeated:

S2D_PlayMusic(mus, true);  // play on a loop

Only one piece of music can be played at a time. The following functions for pausing, resuming, getting and setting volume, stopping, and fading out apply to whatever music is currently playing:

S2D_PauseMusic();
S2D_ResumeMusic();
S2D_StopMusic();

int volume = S2D_GetMusicVolume();
S2D_SetMusicVolume(50);  // set volume 50%

// Fade out over 2000 milliseconds, or 2 seconds
S2D_FadeOutMusic(2000);

Since music is allocated dynamically, free them using:

S2D_FreeMusic(mus);

Input

Simple 2D can capture input from just about anything. Let's learn how to grab input events from the mouse, keyboard, and game controllers.

Keyboard

There are three types of keyboard events captured by the window: when a key is pressed down, a key is being held down, and a key is released. When a keyboard event takes place, the window calls its on_key() function.

To capture keyboard input, first define the on_key() function and read the event details from the S2D_Event structure, for example:

void on_key(S2D_Event e) {
  // Check `e.key` for the key being interacted with

  switch (e.type) {
    case S2D_KEY_DOWN:
      // Key was pressed
      break;

    case S2D_KEY_HELD:
      // Key is being held down
      break;

   case S2D_KEY_UP:
      // Key was released
      break;
  }
}

Then, attach the callback to the window:

window->on_key = on_key;

Mouse

The cursor position of the mouse or trackpad can be read at any time from the window. Note that the top, left corner is the origin, (0, 0).

window->mouse.x;
window->mouse.y;

To capture mouse button input, first define the on_mouse() function and read the event details from the S2D_Event structure, for example:

// `e.button` can be one of:
//   S2D_MOUSE_LEFT
//   S2D_MOUSE_MIDDLE
//   S2D_MOUSE_RIGHT
//   S2D_MOUSE_X1
//   S2D_MOUSE_X2

void on_mouse(S2D_Event e) {
  switch (e.type) {
    case S2D_MOUSE_DOWN:
      // Mouse button was pressed
      // Use `e.button` to see what button was clicked
      // Check `e.dblclick` to see if was a double click
      break;

    case S2D_MOUSE_UP:
      // Mouse button was released
      // Use `e.button` to see what button was clicked
      // Check `e.dblclick` to see if was a double click
      break;

    case S2D_MOUSE_SCROLL:
      // Mouse was scrolled
      // Check `e.direction` for direction being scrolled, normal or inverted:
      //   S2D_MOUSE_SCROLL_NORMAL
      //   S2D_MOUSE_SCROLL_INVERTED
      // Check `e.delta_x` and `e.delta_y` for the difference in x and y position
      break;

    case S2D_MOUSE_MOVE:
      // Mouse was moved
      // Check `e.delta_x` and `e.delta_y` for the difference in x and y position
      break;
  }
}

Then, attach the callback to the window:

window->on_mouse = on_mouse;

Hide the cursor over the window (and show it again) using:

S2D_HideCursor();
S2D_ShowCursor();

Game controllers

All game controllers are automatically detected, added, and removed. There are two types of events captured by the window: axis motion and button presses. When a button is pressed or a joystick moved, the window calls its on_controller() function. Buttons and axes are mapped to a generic Xbox controller layout.

To capture controller input, first define the on_controller() function and read the event details from the S2D_Event structure, for example:

void on_controller(S2D_Event e) {
  // Check `e.which` for the controller being interacted with

  switch (e.type) {
    case S2D_AXIS:
      // Controller axis was moved
      // Use `e.axis` to get the axis, either:
      //   S2D_AXIS_LEFTX, S2D_AXIS_LEFTY,
      //   S2D_AXIS_RIGHTX, S2D_AXIS_RIGHTY,
      //   S2D_AXIS_TRIGGERLEFT, S2D_AXIS_TRIGGERRIGHT,
      //   or S2D_AXIS_INVALID
      // Use `e.value` to get the value of the axis
      break;

    // For the following button events, use `e.button`
    // to get the button pressed or released, which can be:
    //   S2D_BUTTON_A, S2D_BUTTON_B, S2D_BUTTON_X, S2D_BUTTON_Y,
    //   S2D_BUTTON_BACK, S2D_BUTTON_GUIDE, S2D_BUTTON_START,
    //   S2D_BUTTON_LEFTSTICK, S2D_BUTTON_RIGHTSTICK,
    //   S2D_BUTTON_LEFTSHOULDER, S2D_BUTTON_RIGHTSHOULDER,
    //   S2D_BUTTON_DPAD_UP, S2D_BUTTON_DPAD_DOWN,
    //   S2D_BUTTON_DPAD_LEFT, S2D_BUTTON_DPAD_RIGHT,
    //   or S2D_BUTTON_INVALID

    case S2D_BUTTON_DOWN:
      // Controller button was pressed
      break;

    case S2D_BUTTON_UP:
      // Controller button was released
      break;
  }
}

Then, attach the callback to the window:

window->on_controller = on_controller;

See the controller.c test for an exhaustive example of how to interact with game controllers.

You're certain to find controllers that don't yet have button mappings, especially if they're brand new. See the community-sourced database of controller mappings for examples of how to generate mapping strings. Once you have the mapping string, you can register it using S2D_AddControllerMapping(), or add several mappings from a file using S2D_AddControllerMappingsFromFile() and providing the file path.

Contributing

"Simple can be harder than complex: You have to work hard to get your thinking clean to make it simple. But it's worth it in the end because once you get there, you can move mountains." — Steve Jobs

Despite the continuing advancements in computer graphics hardware and software, getting started with simple graphics programming isn't that easy or accessible. We're working to change that.

If you like the project, please consider contributing! Check out the open issues for ideas, or suggest your own. We're always looking for ways to make the project more inviting and improve the developer experience on every platform. Don't worry if you're not an expert in C or graphics APIs — we'll be happy to walk you through it all.

If you are a hardcore C and OS hacker, you should seriously consider contributing to SDL so we can continue writing games without worrying about the platform details underneath. Take a look at the talks from Steam Dev Days, especially Ryan C. Gordon's talk on Game Development with SDL 2.0.

Preparing a release

1. Update dependencies
   • Update SDL versions in simple2d.sh
   • Update SDL and other lib versions in deps/build.sh, run make to rebuild
   • Run git submodule update --remote to update submodules
2. Run tests on all supported platforms
3. Update documentation to reflect the current API
4. Update the version number in simple2d.sh and simple2d.cmd, commit changes
5. Create Windows installers (for Visual C++ and MinGW) and Apple frameworks using the release make/nmake target
6. Create a new release in GitHub, with tag in the form v#.#.#; attach Windows installers and Apple frameworks to release notes
7. Update the Homebrew tap:
   • Update formula with new release archive and frameworks resource URLs
   • Calculate the new sha256 checksums for the release and frameworks archive, using shasum -a 256 <file>
   • Run brew audit --strict ./simple2d.rb to detect any issues with the formula
   • Test installation of the formula using brew install ./simple2d.rb
   • Commit and push changes to the formula
8. 🎉

About the project

Simple 2D was created by Tom Black, who thought simple graphics programming was way too difficult and decided to do something about it.

Everything is MIT Licensed, so hack away.

Enjoy!