[Mesa-dev] gallium st incorrect drawable <-> context bindings.

Jose Fonseca jfonseca at vmware.com
Tue May 24 03:22:56 PDT 2011

----- Original Message -----
> Hi,
> I'm not sure when this use of drawable <-> context bindings started,
> but
> the below commit uses an invalid assumption to fix a problem the root
> cause of which is also an invalid assumption.
> It's incorrect to associate a drawable with a context.
> A drawable may have multiple contexts bound to it, and attempts to
> associate a drawable with a single context will fail miserably in a
> multithreading environment.

This is true for WGL too, although there's some work to be done there too.
> This means that the fix below should be reverted, and
> drawable->driContextPriv should never have been used in the first
> place.
> It should nave no users whatsoever except old dri1 code using it as a
> possible swapbuffer context, but even that usage is undesired.
> Furthermore, the st interface that uses a specific context to notify
> about drawable invalidation is also incorrect. There should be no
> context associated with that.

I assume you're talking about 
st_context_notify_invalid_framebuffer . The point of that function is to notify one context that the drawable changed. But it should notify all of them.

I think right way to fix one-drawable-multiple-contexts is to use a generation number on the drawable, which is incremented whenever the drawable is resized, and then contexts compare it with the last value they saw before.  Would this fit your needs?


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