Patch adding supoort for X Double Buffer extension

[dojothemouse@mac.com]

The OS might want to double buffer any X window for compositing... is 
that what this X feature is for? Does supporting the X Double Buffer 
*force* double buffering, or just allow it?

(P.S. I don't know what I'm talking about.)

On Apr 11, 2004, at 1:51 PM, Samuel Rydh wrote:

> On Sun, Apr 11, 2004 at 07:51:38PM +0000, winden NTW wrote:
>>
>> I'm attaching a patch I did today, please consider adding it for 
>> testing
>> purposes.
>>
>
> Thanks... but why would one want to double buffer the entire 
> framebuffer?
>
> MOL tries very hard to refresh only portions of the display that has 
> changed
> (by utilizing the MMU and by checksumming) in order to reduce the 
> amount of
> data that has to go through the AGP bus. As far as I can see, asking X 
> to
> double buffer will (dramatically) increase the amount of data which
> has to be shuffled. A quick test on my machine shows that this is 
> indeed
> what happens.
>
> As far as I can see, the only possibility to radically speed up the X11
> video driver is using offscreen VRAM for the framebuffer. 
> Unfortunately,
> no good API exists for this (at least I haven't found it).
>
> /Samuel
>
>
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