SDL_RenderReadPixels() needs to flush asynchronous operations before it reads.

The semantics are that it reads the back buffer, and those pixels may not be available once SDL_RenderPresent() has happened.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%404207

test/automated/render/render.c

@@ -329,9 +329,6 @@ static int render_clearScreen (void)
       return -1;
    */
 
-   /* Flush all asynchronous operations */
-   SDL_RenderPresent();
-
    return 0;
 }
 
@@ -413,9 +410,6 @@ static int render_testPrimitives (void)
    if (SDL_ATassert( "SDL_RenderLine", ret == 0))
       return -1;
 
-   /* Flush all asynchronous operations */
-   SDL_RenderPresent();
-
    /* See if it's the same. */
    if (render_compare( "Primitives output not the same.", &img_primitives ))
       return -1;
@@ -533,9 +527,6 @@ static int render_testPrimitivesBlend (void)
       }
    }
 
-   /* Flush all asynchronous operations */
-   SDL_RenderPresent();
-
    /* See if it's the same. */
    if (render_compare( "Blended primitives output not the same.", &img_blend ))
       return -1;
@@ -588,9 +579,6 @@ static int render_testBlit (void)
    /* Clean up. */
    SDL_DestroyTexture( tface );
 
-   /* Flush all asynchronous operations */
-   SDL_RenderPresent();
-
    /* See if it's the same. */
    if (render_compare( "Blit output not the same.", &img_blit ))
       return -1;
@@ -648,9 +636,6 @@ static int render_testBlitColour (void)
    /* Clean up. */
    SDL_DestroyTexture( tface );
 
-   /* Flush all asynchronous operations */
-   SDL_RenderPresent();
-
    /* See if it's the same. */
    if (render_compare( "Blit output not the same (using SDL_SetTextureColorMod).",
             &img_blitColour ))
@@ -713,9 +698,6 @@ static int render_testBlitAlpha (void)
    /* Clean up. */
    SDL_DestroyTexture( tface );
 
-   /* Flush all asynchronous operations */
-   SDL_RenderPresent();
-
    /* See if it's the same. */
    if (render_compare( "Blit output not the same (using SDL_SetSurfaceAlphaMod).",
             &img_blitAlpha ))
@@ -763,9 +745,6 @@ static int render_testBlitBlendMode( SDL_TextureID tface, int mode )
       }
    }
 
-   /* Flush all asynchronous operations */
-   SDL_RenderPresent();
-
    return 0;
 }
 
@@ -883,9 +862,6 @@ static int render_testBlitBlend (void)
    /* Clean up. */
    SDL_DestroyTexture( tface );
 
-   /* Flush all asynchronous operations */
-   SDL_RenderPresent();
-
    /* Check to see if matches. */
    if (render_compare( "Blit blending output not the same (using SDL_BLENDMODE_*).",
             &img_blendAll ))