video: speed up SDL_FillRect[s] slightly (thanks, Jakub!).

"This patch does the following:

* Instead of SDL_FillRects calling SDL_FillRect in a loop the opposite
happens -- SDL_FillRect (a specific case) calls SDL_FillRects (a general case)
with a count of 1

* The switch/case block is moved out of the loop -- it modifies the color
once and stores the fill routine in a pointer which is then used throughout
the loop"

Fixes Bugzilla #4674.

src/video/SDL_fillrect.c

@@ -243,19 +243,8 @@ SDL_FillRect(SDL_Surface * dst, const SDL_Rect * rect, Uint32 color)
         return SDL_SetError("Passed NULL destination surface");
     }
 
-    /* This function doesn't work on surfaces < 8 bpp */
-    if (dst->format->BitsPerPixel < 8) {
-        return SDL_SetError("SDL_FillRect(): Unsupported surface format");
-    }
-
     /* If 'rect' == NULL, then fill the whole surface */
-    if (rect) {
-        /* Perform clipping */
-        if (!SDL_IntersectRect(rect, &dst->clip_rect, &clipped)) {
-            return 0;
-        }
-        rect = &clipped;
-    } else {
+    if (!rect) {
         rect = &dst->clip_rect;
         /* Don't attempt to fill if the surface's clip_rect is empty */
         if (SDL_RectEmpty(rect)) {
@@ -263,13 +252,36 @@ SDL_FillRect(SDL_Surface * dst, const SDL_Rect * rect, Uint32 color)
         }
     }
 
+    return SDL_FillRects(dst, rect, 1, color);
+}
+
+int
+SDL_FillRects(SDL_Surface * dst, const SDL_Rect * rects, int count,
+              Uint32 color)
+{
+    SDL_Rect clipped;
+    Uint8 *pixels;
+    const SDL_Rect* rect;
+    void (*fill_function)(Uint8 * pixels, int pitch, Uint32 color, int w, int h);
+    int i;
+
+    if (!dst) {
+        return SDL_SetError("Passed NULL destination surface");
+    }
+
+    /* This function doesn't work on surfaces < 8 bpp */
+    if (dst->format->BitsPerPixel < 8) {
+        return SDL_SetError("SDL_FillRect(): Unsupported surface format");
+    }
+
     /* Perform software fill */
     if (!dst->pixels) {
         return SDL_SetError("SDL_FillRect(): You must lock the surface");
     }
 
-    pixels = (Uint8 *) dst->pixels + rect->y * dst->pitch +
-                                     rect->x * dst->format->BytesPerPixel;
+    if (!rects) {
+        return SDL_SetError("SDL_FillRects() passed NULL rects");
+    }
 
     switch (dst->format->BytesPerPixel) {
     case 1:
@@ -278,11 +290,11 @@ SDL_FillRect(SDL_Surface * dst, const SDL_Rect * rect, Uint32 color)
             color |= (color << 16);
 #ifdef __SSE__
             if (SDL_HasSSE()) {
-                SDL_FillRect1SSE(pixels, dst->pitch, color, rect->w, rect->h);
+                fill_function = SDL_FillRect1SSE;
                 break;
             }
 #endif
-            SDL_FillRect1(pixels, dst->pitch, color, rect->w, rect->h);
+            fill_function = SDL_FillRect1;
             break;
         }
 
@@ -291,18 +303,18 @@ SDL_FillRect(SDL_Surface * dst, const SDL_Rect * rect, Uint32 color)
             color |= (color << 16);
 #ifdef __SSE__
             if (SDL_HasSSE()) {
-                SDL_FillRect2SSE(pixels, dst->pitch, color, rect->w, rect->h);
+                fill_function = SDL_FillRect2SSE;
                 break;
             }
 #endif
-            SDL_FillRect2(pixels, dst->pitch, color, rect->w, rect->h);
+            fill_function = SDL_FillRect2;
             break;
         }
 
     case 3:
         /* 24-bit RGB is a slow path, at least for now. */
         {
-            SDL_FillRect3(pixels, dst->pitch, color, rect->w, rect->h);
+            fill_function = SDL_FillRect3;
             break;
         }
 
@@ -310,34 +322,32 @@ SDL_FillRect(SDL_Surface * dst, const SDL_Rect * rect, Uint32 color)
         {
 #ifdef __SSE__
             if (SDL_HasSSE()) {
-                SDL_FillRect4SSE(pixels, dst->pitch, color, rect->w, rect->h);
+                fill_function = SDL_FillRect4SSE;
                 break;
             }
 #endif
-            SDL_FillRect4(pixels, dst->pitch, color, rect->w, rect->h);
+            fill_function = SDL_FillRect4;
             break;
         }
     }
 
-    /* We're done! */
-    return 0;
-}
 
-int
-SDL_FillRects(SDL_Surface * dst, const SDL_Rect * rects, int count,
-              Uint32 color)
-{
-    int i;
-    int status = 0;
+    for (i = 0; i < count; ++i) {
+        rect = &rects[i];
+        /* Perform clipping */
+        if (!SDL_IntersectRect(rect, &dst->clip_rect, &clipped)) {
+            continue;
+        }
+        rect = &clipped;
 
-    if (!rects) {
-        return SDL_SetError("SDL_FillRects() passed NULL rects");
-    }
+        pixels = (Uint8 *) dst->pixels + rect->y * dst->pitch +
+                                         rect->x * dst->format->BytesPerPixel;
 
-    for (i = 0; i < count; ++i) {
-        status += SDL_FillRect(dst, &rects[i], color);
+        fill_function(pixels, dst->pitch, color, rect->w, rect->h);
     }
-    return status;
+
+    /* We're done! */
+    return 0;
 }
 
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