[SDL] Windowed OpenGL Performance on OS X

Darrell Walisser walisser at mac.com
Wed Nov 5 16:22:01 PST 2003

> or even worse, rendering, copying to main memory, compositing via 
> Quartz, then
> copying back the framebuffer, which is completley unnecessary.  It 
> should just
> be rendering to a surface in the video card and ignoring all 
> compositing (as it
> should on a machine without QE).

That's right. OpenGL bypasses the Quartz compositor unless other 
windows overlap the OpenGL window. So windowed mode should run near 
fullscreen mode (though fullscreen mode can pageflip on some cards and 
it as more video memory at its disposal so it tends to be faster).

> One other idea is that with the recent 10.3 upgrade, Apple is now doing
> compositing in software even on non-QE enabled systems.  I'll probably 
> test this
> by putting together a GLUT example tonight and seeing how it performs, 
> or by
> placing something transparent on top of the SDL window and seeing if it
> composites correctly (it shouldn't).

It could be that you don't have enough video memory available so it's 
reverting to a software surface. Apple recommends 32MB VRAM for QE, so 
try disabling QE if you've got that enabled and also lowering the 
desktop/window size/depth.

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