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Old 01-15-2010, 09:22 PM   #49
Junior Member
Join Date: Jan 2006
Posts: 19

When it comes to visual appeal, I will agree that OS X looks the least impressive and polished. But the truth of the matter is that under the hood, only the OS X devs actually thought about how to design a proper compositor.

You see the issue is that there's two OpenGL programs running at the same time: the desktop compositor, and the emulator. To pull this off, the operating system redirects the emulator's video surface to an internal texture, and the present command moves the video buffer into the desktop compositor's surface.

Because Windows Aero and Linux Compiz do not properly intercept the Vsync signals to make them always trigger well before the real Vblank, the result is that video always tears and jumps wildly because it's a flip of a coin for which gets updated first: desktop compositor->screen or emulator->desktop compositor? When that order flips, you get a jarring visual effect.

OS X's design ensures it's always the latter first, former second.
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