Doesn't UAE have the option to display using OpenGL? IIRC Sam Jordan's original Mac OS X port did exactly this.
Using OpenGL ought to eliminate the double buffer penalty.
I tried to compile Sam Jordan's version without success.
Where is Sam Jordan's version? (Got an URL?)
I've got some OpenGL toys put together, I'm not much on AGL or Quartz2D coding yet, but I think I get the idea now... I'd rather optimize the QuickDraw into CoreGraphics calls before I worry about the window.
Theoretically, CoreGraphics bitmaps rendered into an OpenGL context would be the best of all worlds. My personal UAE tinkertoy I was working on before this used Cocoa and scaled wonderfully, but was slow as all get out. <sigh>
Your theory is just plain wrong.
You don't have to bother with CoreGraphics at all. You either use an NSBitmapImageRep or an OpenGL view. There is no reason to involve "CoreGraphics bitmaps" or whatever you're trying to say.
The purpose behind using OpenGL is to avoid the duble buffer penalty.