[Cogl] [PATCH 0/7] Quad-buffer stereo support

[Owen Taylor]

On Sun, 2014-06-15 at 17:46 +0100, Robert Bragg wrote:
[...]
> Currently we're missing a way to check renderer features that can help
> you avoid configuring a display with unsupported features. We should
> probably expose a cogl_renderer_has_feature() api. This could expose
> winsys features, such as whether stereo rendering is supported. A
> hacky workaround for the 1.18 branch could be to expose another
> COGL_WINSYS_FEATURE_ that clutter can access via
> cogl_clutter_winsys_has_feature().

cogl_clutter_winsys_has_feature() seems to just be a default-context
version of cogl_has_feature(), and implicitly relies on a CoglContext -
so I don't see how it works for information that we need before
creating a CoglContext.

There's also a bit of a problem that GL specifies things in terms of a
list of fbconfigs without requiring all combinations to be present - so
cogl_renderer_has_feature(renderer, ALPHA_WINDOWS) and
cogl_renderer_has_feature(renderer, STEREO) could be individually
supported but not the combination.

If there's a desire to avoid fallbacks inside Cogl, then I'm not sure
there's a better approach than simply having Clutter try configurations
until it finds one that works.

- Owen