Added support for custom shaders with the GPU renderer

Added an example of MSDF font rendering with the SDL 2D renderer

include/SDL3/SDL_render.h

@@ -59,6 +59,7 @@
 #include <SDL3/SDL_rect.h>
 #include <SDL3/SDL_surface.h>
 #include <SDL3/SDL_video.h>
+#include <SDL3/SDL_gpu.h>
 
 #include <SDL3/SDL_begin_code.h>
 /* Set up for C function definitions, even when using C++ */
@@ -2709,6 +2710,117 @@ extern SDL_DECLSPEC bool SDLCALL SDL_SetDefaultTextureScaleMode(SDL_Renderer *re
  */
 extern SDL_DECLSPEC bool SDLCALL SDL_GetDefaultTextureScaleMode(SDL_Renderer *renderer, SDL_ScaleMode *scale_mode);
 
+/**
+ * GPU render state description.
+ *
+ * This structure should be initialized using SDL_INIT_INTERFACE().
+ *
+ * \since This struct is available since SDL 3.4.0.
+ *
+ * \sa SDL_CreateGPURenderState
+ */
+typedef struct SDL_GPURenderStateDesc
+{
+    Uint32 version;                 /**< the version of this interface */
+
+    SDL_GPUShader *fragment_shader; /**< The fragment shader to use when this render state is active */
+
+    Sint32 num_sampler_bindings;    /**< The number of additional fragment samplers to bind when this render state is active */
+    const SDL_GPUTextureSamplerBinding *sampler_bindings;   /** Additional fragment samplers to bind when this render state is active */
+
+    Sint32 num_storage_textures;    /**< The number of storage textures to bind when this render state is active */
+    SDL_GPUTexture *const *storage_textures;    /** Storage textures to bind when this render state is active */
+
+    Sint32 num_storage_buffers;    /**< The number of storage buffers to bind when this render state is active */
+    SDL_GPUBuffer *const *storage_buffers;      /** Storage buffers to bind when this render state is active */
+} SDL_GPURenderStateDesc;
+
+/* Check the size of SDL_GPURenderStateDesc
+ *
+ * If this assert fails, either the compiler is padding to an unexpected size,
+ * or the interface has been updated and this should be updated to match and
+ * the code using this interface should be updated to handle the old version.
+ */
+SDL_COMPILE_TIME_ASSERT(SDL_GPURenderStateDesc_SIZE,
+    (sizeof(void *) == 4 && sizeof(SDL_GPURenderStateDesc) == 32) ||
+    (sizeof(void *) == 8 && sizeof(SDL_GPURenderStateDesc) == 64));
+
+/**
+ * A custom GPU render state.
+ *
+ * \since This struct is available since SDL 3.4.0.
+ *
+ * \sa SDL_CreateGPURenderState
+ * \sa SDL_SetGPURenderStateFragmentUniformData
+ * \sa SDL_SetRenderGPUState
+ * \sa SDL_DestroyGPURenderState
+ */
+typedef struct SDL_GPURenderState SDL_GPURenderState;
+
+/**
+ * Create custom GPU render state.
+ *
+ * \param renderer the renderer to use.
+ * \param desc GPU render state description, initialized using SDL_INIT_INTERFACE().
+ * \returns a custom GPU render state or NULL on failure; call SDL_GetError() for more information.
+ *
+ * \threadsafety This function should be called on the thread that created the renderer.
+ *
+ * \since This function is available since SDL 3.4.0.
+ *
+ * \sa SDL_SetGPURenderStateFragmentUniformData
+ * \sa SDL_SetRenderGPUState
+ * \sa SDL_DestroyGPURenderState
+ */
+extern SDL_DECLSPEC SDL_GPURenderState * SDLCALL SDL_CreateGPURenderState(SDL_Renderer *renderer, SDL_GPURenderStateDesc *desc);
+
+/**
+ * Set fragment shader uniform variables in a custom GPU render state.
+ *
+ * The data is copied and will be pushed using SDL_PushGPUFragmentUniformData() during draw call execution.
+ *
+ * \param state the state to modify.
+ * \param slot_index the fragment uniform slot to push data to.
+ * \param data client data to write.
+ * \param length the length of the data to write.
+ * \returns true on success or false on failure; call SDL_GetError() for more
+ *          information.
+ *
+ * \threadsafety This function should be called on the thread that created the renderer.
+ *
+ * \since This function is available since SDL 3.4.0.
+ */
+extern SDL_DECLSPEC bool SDLCALL SDL_SetGPURenderStateFragmentUniformData(SDL_GPURenderState *state, Uint32 slot_index, const void *data, Uint32 length);
+
+/**
+ * Set custom GPU render state.
+ *
+ * This function sets custom GPU render state for subsequent draw calls. This allows using custom shaders with the GPU renderer.
+ *
+ * \param renderer the renderer to use.
+ * \param state the state to to use, or NULL to clear custom GPU render state.
+ * \returns true on success or false on failure; call SDL_GetError() for more
+ *          information.
+ *
+ * \threadsafety This function should be called on the thread that created the renderer.
+ *
+ * \since This function is available since SDL 3.4.0.
+ */
+extern SDL_DECLSPEC bool SDLCALL SDL_SetRenderGPUState(SDL_Renderer *renderer, SDL_GPURenderState *state);
+
+/**
+ * Destroy custom GPU render state.
+ *
+ * \param state the state to destroy.
+ *
+ * \threadsafety This function should be called on the thread that created the renderer.
+ *
+ * \since This function is available since SDL 3.4.0.
+ *
+ * \sa SDL_CreateGPURenderState
+ */
+extern SDL_DECLSPEC void SDLCALL SDL_DestroyGPURenderState(SDL_GPURenderState *state);
+
 /* Ends C function definitions when using C++ */
 #ifdef __cplusplus
 }