questions about GEM buffer object

Wang Baisheng at
Sun Oct 16 19:09:50 PDT 2011

2011/10/15 Ian Romanick <idr at>

> On 10/10/2011 10:25 PM, Wang Baisheng wrote:
>> Hi All:
>> I have some confused for the GEM buffer object. There must be one GEM
>> buffer object for the framebuffer to be displayed on screen, right ? And
>> for every window, there is also one GEM buffer object, right ? If so, my
>> question is:
>> Is the GEM buffer object for the window (not direct rendering, just for
>> 2D X client window)  just pointed to some part of the displayed
>> framebuffer, and any drawing operation is happened on the framebuffer ?
>> Or another new memory is allocated for window and then at some time the
>> buffer object for window is copied to the displayed framebuffer ?
> In a composited desktop, there is a GEM buffer for each window.  The
> compositor combines the images from all the windows into the screen.

So in a non-composited desktop, all windows use the scanout buffer, and all
drawing operations happen in scanout buffer, will this cause flicker or
tearing ?
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