questions about GEM buffer object

Ian Romanick idr at
Fri Oct 14 10:44:49 PDT 2011

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.

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