[Qt-interest] Partial updates with double buffering

[Arnaud Vrac]

Hi,

I'm using the opengl graphics system with an SGX chip and partial
updates work fine with single and double buffering. However,
performance is not as good in double buffering as in single buffering.
This is due to the fact that the opengl driver copies the front buffer
to the back buffer when swapping buffers. It seems the implementation
of partial updates for the GL window surface relies on this. However,
the buffer copy can be avoided when changing some code in the WSEGL
library. But if this copy is not done, partial updates need to be
spanned the last two frames instead of only the last one. Is it
possible to do that with the current Qt code ?

Note: the copy can be avoided by setting changing the WSEGL
implementation of GetDrawableParameters to set the parameters of the
current buffer for both the source and render surfaces (instead of the
previous and current buffer).

Regards

-- 
Arnaud Vrac