spine-sdl Runtime Documentation

Licensing

Please see the Spine Runtimes License before integrating the Spine Runtimes into your applications.

Getting Started

spine-sdl is a C and C++ based runtime to load, manipulate and render Spine skeletons with SDL.

spine-sdl requires SDL 2.0.18+ and supports all Spine features except two-color tinting.

Installation

The spine-sdl runtime is available as a C and C++ API. Both APIs are based on spine-c and spine-cpp runtimes. Note that spine-c depends on spine-cpp, so both are required regardless of which API you choose to use.

Integration with CMake (Recommended)

The easiest way to integrate spine-sdl into your project is via CMake FetchContent:

cmake
cmake_minimum_required(VERSION 3.16)
project(MySpineProject)

include(FetchContent)
FetchContent_Declare(
   spine-sdl
   GIT_REPOSITORY https://github.com/esotericsoftware/spine-runtimes.git
   GIT_TAG 4.3
   SOURCE_SUBDIR spine-sdl
)
FetchContent_MakeAvailable(spine-sdl)

# Create your executable
add_executable(MyApp main.cpp)

# For C API
target_link_libraries(MyApp spine-sdl-c)

# For C++ API
target_link_libraries(MyApp spine-sdl-cpp)

This will automatically fetch and build spine-sdl along with all its dependencies (spine-c, spine-cpp, and SDL).

Manual Integration

If you prefer manual integration:

  1. Download the Spine Runtimes source using git (git clone https://github.com/esotericsoftware/spine-runtimes) or download as a zip.
  2. Add the required source files to your project:
    • For C API: Add sources from spine-cpp/src, spine-c/src, and spine-sdl/src/spine-sdl-c.c
    • For C++ API: Add sources from spine-cpp/src, spine-c/src, and spine-sdl/src/spine-sdl-cpp.cpp

  3. Add the include directories: spine-cpp/include, spine-c/include, and spine-sdl/src
  4. Link against SDL2

In your C or C++ code, include either of the following header files to get access to the spine-sdl API:

C++
// C API
#include <spine-sdl-c.h>

// C++ API
#include <spine-sdl-cpp.h>

Note: spine-sdl requires the SDL_RenderGeometry API which is available since SDL 2.0.18. Earlier versions of SDL are not compatible with spine-sdl.

Samples

The spine-sdl example works on Windows, Linux and Mac OS X. For a spine-c based example, see example/main.c, for a spine-cpp example see example/main.cpp.

Windows

  1. Install Visual Studio Community. Make sure you install support for C++ and CMake.
  2. Download the Spine Runtimes repository using git (git clone https://github.com/esotericsoftware/spine-runtimes) or download it as a zip.
  3. Open Visual Studio Community, then open spine-sdl/ via the Open a local folder button in the Visual Studio Community launcher.
  4. Wait for CMake to finish, then select either spine-sdl-c-example.exe or spine-sdl-cpp-example.exe as the start-up project and start debugging.

Linux

  1. Install dependencies:
    bash
    sudo apt-get install cmake ninja-build # Ubuntu/Debian
    # or equivalent for your distribution
  2. Clone the repository: git clone https://github.com/esotericsoftware/spine-runtimes
  3. Build and run:
    bash
    cd spine-runtimes/spine-sdl
    ./build.sh
    ./build/debug/spine-sdl-c-example   # Run C example
    ./build/debug/spine-sdl-cpp-example # Run C++ example

macOS

  1. Install Xcode
  2. Install Homebrew
  3. Install dependencies:
    bash
    brew install cmake ninja
  4. Clone the repository: git clone https://github.com/esotericsoftware/spine-runtimes
  5. Build and run:
    bash
    cd spine-runtimes/spine-sdl
    ./build.sh
    ./build/debug/spine-sdl-c-example   # Run C example
    ./build/debug/spine-sdl-cpp-example # Run C++ example

Using spine-sdl

The spine-sdl runtime supports playback and manipulation of animations created with Spine with SDL. The spine-sdl runtime comes as both a C and C++ implementation, based on the generic spine-c and spine-cpp runtimes. It adds loading and rendering implementations based on the SDL APIs.

Please consult the Spine Runtimes Guide for a detailed overview of the Spine Runtime architecture, and the spine-c and spine-cpp documentation for information on the core APIs used to playback and manipulate animations created with Spine with C and C++.

Exporting for SDL

Please follow the instructions in the Spine User Guide on how to

  1. Export skeleton & animation data
  2. Export texture atlases containing the images of your skeleton

An export of the skeleton data and texture atlas of your skeleton will yield the following files:

  1. skeleton-name.json or skeleton-name.skel, containing your skeleton and animation data.
  2. skeleton-name.atlas, containing information about the texture atlas.
  3. One or more .png files, each representing on page of your texture atlas containing the packed images your skeleton uses.

Note: The spine-sdl runtime does not support two-color tinting.

Loading Spine skeletons

The spine-sdl runtime uses the SDL_Renderer API to display skeletons. Before a skeleton can be loaded from exported files, an SDL_Renderer must be created:

C++
SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);

Loading with C API

With the spine-c API, loading requires texture loading callbacks and manual file reading:

C++
// Global renderer for texture loading callbacks
static SDL_Renderer *g_renderer;

// Texture loading callbacks
void *load_texture_callback(const char *path) {
   extern void *load_texture(const char *path, SDL_Renderer *renderer);
   return load_texture(path, g_renderer);
}

void unload_texture_callback(void *texture) {
   SDL_DestroyTexture((SDL_Texture*)texture);
}

// Set the global renderer
g_renderer = renderer;

// Read atlas file into memory
int atlas_length;
char *atlas_data = read_file("data/spineboy-pma.atlas", &atlas_length);

// Load atlas with callbacks
spine_atlas_result atlas_result = spine_atlas_load_callback(
   atlas_data, "data/", load_texture_callback, unload_texture_callback);
spine_atlas atlas = spine_atlas_result_get_atlas(atlas_result);

// Read skeleton file into memory
int skeleton_length;
char *skeleton_data = read_file("data/spineboy-pro.json", &skeleton_length);

// Load skeleton data
spine_skeleton_data_result skeleton_result = spine_skeleton_data_load_json(
   atlas, skeleton_data, "data/");
spine_skeleton_data skeleton_data_handle = spine_skeleton_data_result_get_data(skeleton_result);

// Free file data
free(atlas_data);
free(skeleton_data);

Loading with C++ API

For the C++ API, a SDLTextureLoader is needed:

C++
// C++ API
spine::SDLTextureLoader textureLoader(renderer);
spine::Atlas atlas("data/spineboy-pma.atlas", &textureLoader);
spine::SkeletonJson json(atlas);
spine::SkeletonData *skeletonData = json.readSkeletonDataFile("data/spineboy-pro.json");

The loaded skeleton data and atlas can and should be shared across skeleton instances to reduce memory consumption and enable batched rendering of skeletons that share the same atlas data.

Rendering Skeletons

spine-sdl provides simple rendering functions that work directly with skeletons and skeleton drawables.

C API

C++
// Create skeleton drawable (combines skeleton + animation state)
spine_skeleton_drawable drawable = spine_skeleton_drawable_create(skeleton_data_handle);
spine_skeleton skeleton = spine_skeleton_drawable_get_skeleton(drawable);
spine_animation_state animation_state = spine_skeleton_drawable_get_animation_state(drawable);

// Setup skeleton
spine_skeleton_set_position(skeleton, 400, 500);
spine_skeleton_set_scale(skeleton, 0.5f, 0.5f);
spine_skeleton_setup_pose(skeleton);

// Setup animation
spine_animation_state_set_animation_1(animation_state, 0, "portal", false);
spine_animation_state_add_animation_1(animation_state, 0, "run", true, 0);

// Update and render (in your main loop)
spine_skeleton_drawable_update(drawable, deltaTime);
spine_sdl_draw(drawable, renderer, true); // true for premultiplied alpha

// Or draw skeleton directly without drawable
spine_sdl_draw_skeleton(skeleton, renderer, true);

// Cleanup
spine_skeleton_drawable_dispose(drawable);
spine_skeleton_data_dispose(skeleton_data_handle);
spine_atlas_dispose(atlas);
spine_skeleton_data_result_dispose(skeleton_result);
spine_atlas_result_dispose(atlas_result);

C++ API

C++
// Create skeleton and animation state
spine::Skeleton skeleton(*skeletonData);
spine::AnimationStateData animationStateData(*skeletonData);
spine::AnimationState animationState(animationStateData);

// Setup skeleton
skeleton.setPosition(400, 500);
skeleton.setupPose();

// Setup animation
animationState.setAnimation(0, "portal", false);
animationState.addAnimation(0, "run", true, 0);

// Update and render (in your main loop)
animationState.update(deltaTime);
animationState.apply(skeleton);
skeleton.update(deltaTime);
skeleton.updateWorldTransform(spine::Physics_Update);

// Draw using the simple SDL_draw function
spine::SDL_draw(skeleton, renderer, true); // true for premultiplied alpha

// Cleanup
delete skeletonData;
delete &atlas;

Please refer to the spine-c and spine-cpp documentation for more information on the APIs to manipulate skeletons and animation states.

Cleanup

When you no longer need the skeleton and atlas data, free their memory:

C API

C++
// Dispose skeleton drawable and data
spine_skeleton_drawable_dispose(drawable);
spine_skeleton_data_dispose(skeleton_data_handle);
spine_atlas_dispose(atlas);
spine_skeleton_data_result_dispose(skeleton_result);
spine_atlas_result_dispose(atlas_result);

// Free manually allocated file data
free(atlas_data);
free(skeleton_data);

C++ API

C++
// C++ API cleanup
delete skeletonData;
delete &atlas; // If allocated with new

Note: Freeing skeleton data and atlas instances will automatically dispose of any associated SDL textures through the texture loader.