GTK progressbar call on XRenderComposite

[Jonathan Morton]

On Thu, 2010-05-20 at 16:11 +0800, Huang, FrankR wrote:

> I have use XFlush in cairo to send the XRenderComposite to server, but
> still can not see every step result on the screen. Only the final
> progressbar is displayed. So it is hard for me to trace the render
> process of a progressbar.

The rendering is almost certainly done using a backbuffer, a common
technique for eliminating flicker from a rendering process.  The
backbuffer is not part of the screen, but the final Composite call
copies it to the screen in the correct place.

If you were to direct the same sequence of calls, minus the final one,
directly to the screen, you would in theory see the bar being rendered.
On a modern computer this would happen too quickly to see clearly (but
would still flicker annoyingly), so you would also want to insert delays
to make the process visible if you want to learn about the process.

-- 
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From: Jonathan Morton
      jonathan.morton at movial.com