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Fixed bug #1026

 Vittorio Giovara      2010-07-16 19:09:28 PDT

i was reading SDL_renderer_gles and i noticed that every time we there
is some gl call the gl state is modified with a couple of
glEnableClientState()/glDisableClientState.
While this is completely fine for desktops systems, this is a major
performace kill on mobile devices, right where opengles is
implemented.
Normal practice in this case is to update the glstate once, keep it
always the same and disable/enable other states only in very special
occasions.

On the web there's plenty of documentation (on the top of my head
http://developer.apple.com/iphone/library/documentation/3DDrawing/Conceptual/OpenGLES_ProgrammingGuide/Performance/Performance.html#//apple_ref/doc/uid/TP40008793-CH105-SW5
) and i personally tried this.
I modified my code and got a 10 fps boost, then modified SDL_render_gles and
shifted from 40 fps to 50 fps alone -- considering that i started from ~30fps i
got an 80% performance increase with this technique.

I have attached a dif of my changes, hope that it will be included in
mainstream.
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slouken committed Jan 20, 2011
1 parent 96a32c9 commit 52a5d71528b0f6e883288c46ac02c721c3aa34c4
Showing with 3 additions and 12 deletions.
  1. +3 −12 src/video/SDL_renderer_gles.c
@@ -324,6 +324,9 @@ GLES_CreateRenderer(SDL_Window * window, Uint32 flags)
data->glDisable(GL_CULL_FACE);
data->updateSize = SDL_TRUE;

data->glEnableClientState(GL_VERTEX_ARRAY);
data->glEnableClientState(GL_TEXTURE_COORD_ARRAY);

return renderer;
}

@@ -690,9 +693,7 @@ GLES_RenderDrawPoints(SDL_Renderer * renderer, const SDL_Point * points,
vertices[2*i+1] = (GLshort)points[i].y;
}
data->glVertexPointer(2, GL_SHORT, 0, vertices);
data->glEnableClientState(GL_VERTEX_ARRAY);
data->glDrawArrays(GL_POINTS, 0, count);
data->glDisableClientState(GL_VERTEX_ARRAY);
SDL_stack_free(vertices);

return 0;
@@ -719,7 +720,6 @@ GLES_RenderDrawLines(SDL_Renderer * renderer, const SDL_Point * points,
vertices[2*i+1] = (GLshort)points[i].y;
}
data->glVertexPointer(2, GL_SHORT, 0, vertices);
data->glEnableClientState(GL_VERTEX_ARRAY);
if (count > 2 &&
points[0].x == points[count-1].x && points[0].y == points[count-1].y) {
/* GL_LINE_LOOP takes care of the final segment */
@@ -728,7 +728,6 @@ GLES_RenderDrawLines(SDL_Renderer * renderer, const SDL_Point * points,
} else {
data->glDrawArrays(GL_LINE_STRIP, 0, count);
}
data->glDisableClientState(GL_VERTEX_ARRAY);
SDL_stack_free(vertices);

return 0;
@@ -748,7 +747,6 @@ GLES_RenderDrawRects(SDL_Renderer * renderer, const SDL_Rect ** rects,
(GLfloat) renderer->b * inv255f,
(GLfloat) renderer->a * inv255f);

data->glEnableClientState(GL_VERTEX_ARRAY);
for (i = 0; i < count; ++i) {
const SDL_Rect *rect = rects[i];
GLshort minx = rect->x;
@@ -768,7 +766,6 @@ GLES_RenderDrawRects(SDL_Renderer * renderer, const SDL_Rect ** rects,
data->glVertexPointer(2, GL_SHORT, 0, vertices);
data->glDrawArrays(GL_LINE_LOOP, 0, 4);
}
data->glDisableClientState(GL_VERTEX_ARRAY);

return 0;
}
@@ -787,7 +784,6 @@ GLES_RenderFillRects(SDL_Renderer * renderer, const SDL_Rect ** rects,
(GLfloat) renderer->b * inv255f,
(GLfloat) renderer->a * inv255f);

data->glEnableClientState(GL_VERTEX_ARRAY);
for (i = 0; i < count; ++i) {
const SDL_Rect *rect = rects[i];
GLshort minx = rect->x;
@@ -807,7 +803,6 @@ GLES_RenderFillRects(SDL_Renderer * renderer, const SDL_Rect ** rects,
data->glVertexPointer(2, GL_SHORT, 0, vertices);
data->glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
}
data->glDisableClientState(GL_VERTEX_ARRAY);

return 0;
}
@@ -950,12 +945,8 @@ GLES_RenderCopy(SDL_Renderer * renderer, SDL_Texture * texture,
texCoords[7] = maxv;

data->glVertexPointer(2, GL_SHORT, 0, vertices);
data->glEnableClientState(GL_VERTEX_ARRAY);
data->glTexCoordPointer(2, GL_FLOAT, 0, texCoords);
data->glEnableClientState(GL_TEXTURE_COORD_ARRAY);
data->glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
data->glDisableClientState(GL_TEXTURE_COORD_ARRAY);
data->glDisableClientState(GL_VERTEX_ARRAY);
}

data->glDisable(GL_TEXTURE_2D);

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