render: Move to a batching system for rendering (work in progress).

include/SDL_hints.h

@@ -1029,6 +1029,31 @@ extern "C" {
  */
 #define SDL_HINT_AUDIO_CATEGORY   "SDL_AUDIO_CATEGORY"
 
+/**
+ *  \brief  A variable controlling whether the 2D render API is compatible or efficient.
+ *
+ *  This variable can be set to the following values:
+ *
+ *    "0"     - Don't use batching to make rendering more efficient.
+ *    "1"     - Use batching, but might cause problems if app makes its own direct OpenGL calls.
+ *
+ *  Up to SDL 2.0.9, the render API would draw immediately when requested. Now
+ *  it batches up draw requests and sends them all to the GPU only when forced
+ *  to (during SDL_RenderPresent, when changing render targets, by updating a
+ *  texture that the batch needs, etc). This is significantly more efficient,
+ *  but it can cause problems for apps that expect to render on top of the
+ *  render API's output. As such, SDL will disable batching if a specific
+ *  render backend is requested (since this might indicate that the app is
+ *  planning to use the underlying graphics API directly). This hint can
+ *  be used to explicitly request batching in this instance. It is a contract
+ *  that you will either never use the underlying graphics API directly, or
+ *  if you do, you will call SDL_RenderFlush() before you do so any current
+ *  batch goes to the GPU before your work begins. Not following this contract
+ *  will result in undefined behavior.
+ */
+#define SDL_HINT_RENDER_BATCHING  "SDL_RENDER_BATCHING"
+
+
 /**
  *  \brief  An enumeration of hint priorities
  */

src/render/SDL_sysrender.h

@@ -75,12 +75,51 @@ struct SDL_Texture
     int pitch;
     SDL_Rect locked_rect;
 
+    Uint32 last_command_generation; /* last command queue generation this texture was in. */
+
     void *driverdata;           /**< Driver specific texture representation */
 
     SDL_Texture *prev;
     SDL_Texture *next;
 };
 
+typedef enum
+{
+    SDL_RENDERCMD_NO_OP,
+    SDL_RENDERCMD_SETVIEWPORT,
+    SDL_RENDERCMD_SETCLIPRECT,
+    SDL_RENDERCMD_CLEAR,
+    SDL_RENDERCMD_DRAW_POINTS,
+    SDL_RENDERCMD_DRAW_LINES,
+    SDL_RENDERCMD_FILL_RECTS,
+    SDL_RENDERCMD_COPY,
+    SDL_RENDERCMD_COPY_EX
+} SDL_RenderCommandType;
+
+typedef struct SDL_RenderCommand
+{
+    SDL_RenderCommandType command;
+    union {
+        SDL_Rect viewport;
+        struct {
+            SDL_bool enabled;
+            SDL_Rect rect;
+        } cliprect;
+        struct {
+            size_t first;
+            size_t count;
+            Uint8 r, g, b, a;
+            SDL_BlendMode blend;
+            SDL_Texture *texture;
+        } draw;
+        struct {
+            Uint8 r, g, b, a;
+        } color;
+    } data;
+    struct SDL_RenderCommand *next;
+} SDL_RenderCommand;
+
+
 /* Define the SDL renderer structure */
 struct SDL_Renderer
 {
@@ -90,12 +129,18 @@ struct SDL_Renderer
     int (*GetOutputSize) (SDL_Renderer * renderer, int *w, int *h);
     SDL_bool (*SupportsBlendMode)(SDL_Renderer * renderer, SDL_BlendMode blendMode);
     int (*CreateTexture) (SDL_Renderer * renderer, SDL_Texture * texture);
-    int (*SetTextureColorMod) (SDL_Renderer * renderer,
-                               SDL_Texture * texture);
-    int (*SetTextureAlphaMod) (SDL_Renderer * renderer,
-                               SDL_Texture * texture);
-    int (*SetTextureBlendMode) (SDL_Renderer * renderer,
-                                SDL_Texture * texture);
+    int (*QueueDrawPoints) (SDL_Renderer * renderer, SDL_RenderCommand *cmd, const SDL_FPoint * points,
+                             int count);
+    int (*QueueDrawLines) (SDL_Renderer * renderer, SDL_RenderCommand *cmd, const SDL_FPoint * points,
+                            int count);
+    int (*QueueFillRects) (SDL_Renderer * renderer, SDL_RenderCommand *cmd, const SDL_FRect * rects,
+                            int count);
+    int (*QueueCopy) (SDL_Renderer * renderer, SDL_RenderCommand *cmd, SDL_Texture * texture,
+                       const SDL_Rect * srcrect, const SDL_FRect * dstrect);
+    int (*QueueCopyEx) (SDL_Renderer * renderer, SDL_RenderCommand *cmd, SDL_Texture * texture,
+                        const SDL_Rect * srcquad, const SDL_FRect * dstrect,
+                        const double angle, const SDL_FPoint *center, const SDL_RendererFlip flip);
+    int (*RunCommandQueue) (SDL_Renderer * renderer, SDL_RenderCommand *cmd, void *vertices, size_t vertsize);
     int (*UpdateTexture) (SDL_Renderer * renderer, SDL_Texture * texture,
                           const SDL_Rect * rect, const void *pixels,
                           int pitch);
@@ -108,20 +153,6 @@ struct SDL_Renderer
                         const SDL_Rect * rect, void **pixels, int *pitch);
     void (*UnlockTexture) (SDL_Renderer * renderer, SDL_Texture * texture);
     int (*SetRenderTarget) (SDL_Renderer * renderer, SDL_Texture * texture);
-    int (*UpdateViewport) (SDL_Renderer * renderer);
-    int (*UpdateClipRect) (SDL_Renderer * renderer);
-    int (*RenderClear) (SDL_Renderer * renderer);
-    int (*RenderDrawPoints) (SDL_Renderer * renderer, const SDL_FPoint * points,
-                             int count);
-    int (*RenderDrawLines) (SDL_Renderer * renderer, const SDL_FPoint * points,
-                            int count);
-    int (*RenderFillRects) (SDL_Renderer * renderer, const SDL_FRect * rects,
-                            int count);
-    int (*RenderCopy) (SDL_Renderer * renderer, SDL_Texture * texture,
-                       const SDL_Rect * srcrect, const SDL_FRect * dstrect);
-    int (*RenderCopyEx) (SDL_Renderer * renderer, SDL_Texture * texture,
-                       const SDL_Rect * srcquad, const SDL_FRect * dstrect,
-                       const double angle, const SDL_FPoint *center, const SDL_RendererFlip flip);
     int (*RenderReadPixels) (SDL_Renderer * renderer, const SDL_Rect * rect,
                              Uint32 format, void * pixels, int pitch);
     void (*RenderPresent) (SDL_Renderer * renderer);
@@ -178,6 +209,16 @@ struct SDL_Renderer
     Uint8 r, g, b, a;                   /**< Color for drawing operations values */
     SDL_BlendMode blendMode;            /**< The drawing blend mode */
 
+    SDL_bool batching;
+    SDL_RenderCommand *render_commands;
+    SDL_RenderCommand *render_commands_tail;
+    SDL_RenderCommand *render_commands_pool;
+    Uint32 render_command_generation;
+
+    void *vertex_data;
+    size_t vertex_data_used;
+    size_t vertex_data_allocation;
+
     void *driverdata;
 };
 
@@ -209,6 +250,11 @@ extern SDL_BlendFactor SDL_GetBlendModeSrcAlphaFactor(SDL_BlendMode blendMode);
 extern SDL_BlendFactor SDL_GetBlendModeDstAlphaFactor(SDL_BlendMode blendMode);
 extern SDL_BlendOperation SDL_GetBlendModeAlphaOperation(SDL_BlendMode blendMode);
 
+/* drivers call this during their Queue*() methods to make space in a array that are used
+   for a vertex buffer during RunCommandQueue(). Pointers returned here are only valid until
+   the next call, because it might be in an array that gets realloc()'d. */
+extern void *SDL_AllocateRenderVertices(SDL_Renderer *renderer, const size_t numbytes, size_t *offset);
+
 #endif /* SDL_sysrender_h_ */
 
 /* vi: set ts=4 sw=4 expandtab: */