[cairo] Re: [Mesa3d-dev] OpenGL and Cairo

Jon Smirl jonsmirl at yahoo.com
Wed Apr 21 18:43:53 PDT 2004

--- Vladimir Vukicevic <vladimir at pobox.com> wrote:
> In addition to asking whether Cairo+glitz+OpenGL will be good enough to 
> compete, I wonder if GLX will be able to stand up to the task. 
> Specifically, if you need opengl across the entire desktop, will GLX be 
> able to handle the multiple contexts and other interactions needed? 
> What if I want to run a native OpenGL app (3d editor, game, etc.) on top 
> of this OpenGL-based desktop?   If you limit things to interacting with 
> 2d windows + xrender for compositing those windows at the top level, 
> things might get simpler, but I think you would also lose functionality 
> at that point.

You can already run multiple OpenGL apps on X today. The desktop will just be
another one. Clipping is used to keep the apps from interfering with each other.
This is no different than running one OpenGL app and dragging it on top of

The chips only have one context in them. When X activates a different window the
OpenGL implementation causes another context to be loaded from RAM.

Hardware accelerated pbuffer suppport is key to the compositing window manager.
Apps will draw into a pbuffer and then the compositor will render the app's
pbuffer to the screen while applying the appropriate transformations.

> mesa-solo looks quite interesting, but unless I'm missing something, at 
> that point you would essentially be dumping X -- I'm not sure that is 
> really a feasable thing?

The idea behind mesa solo is to give the entire X 2D driver system the boot. X
would use mesa/OpenGL to draw everything. X is still there providing API
compatibility and a window manager. You would always use glitz in the this model
for Cairo support.

The prime reason for this is that everything will be hardware accelerated. The
plan is to get xserver running on mesa-solo as a model. Then encourage
Nvidia/ATI to do solo versions of their OpenGL implementations. Nvidia/ATI
already have excellent OpenGL implementation, the would just need to convert
them to run standalone.

This is the same model Microsoft is using in Longhorn. The 2D driver system has
been eliminated in favor of D3D. User space API compatibility is still
maintained but internally everything gets drawn using D3D.

> 	- Vlad

Jon Smirl
jonsmirl at yahoo.com

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