[cairo] Win32/OpenGL

[Vladimir Vukicevic]

On 1/15/06, Stéphane LOEUILLET <leroutier at gmail.com> wrote:
> hello,
>
> > As Windows Vista is likely to "emulate" OpenGL 1.4 (not even 2.0) by
> > mapping OpenGL calls to directx. Would it make sense then to use directx
> > rather then OpenGL as cairo backend on windows? I have program that will
> > use cairo and unfortunate majority of my customers use Windows so I am
> > concerned by this issue.
>
> Vista would emulate OpenGL only if your driver doesn't provide an ICD
> (like it does actually)
> with XP and lower, it emulates GL 1.1 in pure software if no ICD
> present. only change is that it would emulate GL 1.4, partly
> accelerated via Dx.

That's actually not true; with Vista, if you're using the Aero Glass
interface, the entire display is rendered using DirectX (Next).  To
provide windowed OpenGL support on top of Aero Glass, OpenGL is
emulated using DirectX, fixed at OpenGL 1.4 functionality.  The
driver's OpenGL ICD is not involved, unless a) the app is fullscreen
[e.g. games], b) or the user switches to the Windows XP/2000 interface
[and loses all the aero glass fancy effects, etc].  Take a look at
http://www.opengl.org/discussion_boards/cgi_directory/ultimatebb.cgi?ubb=get_topic;f=12;t=000001
for some more information.

We at Mozilla would like to support 3D-accelerated rendering; we were
talking about a possible DirectX backend for cairo, but we won't have
resources to work on that for quite some time.  It would be great if
someone were to start working on it.

- Vlad