wined3d: Bind device framebuffer in ActivateContext

[Allan Tong]

> The framebuffer setup should be merged with ActivateContext, but not by simply
> setting the framebuffer to 0. Currently there are two issues: the one you are
> seeing(the complaints from opengl), and multithreading issues.
>
> Parts of the code call ActivateContext before setting the fbo: In this case
> you can get errors in glDrawBuffers. Other parts call the fbo setup before
> calling ActivateContext. In this case the app can crash after a rendering
> thread switch because no GL context is active.

Ah, ok, I think I've seen the threading issues as well.

> The whole issue is pretty complex unfortunately. One issue is that we cannot
> select context and drawable separately for onscreen rendering, and pbuffer
> offscreen rendering. In the case of fbos, the drawable can be set without
> changing the context.
>
> Another issue is that ActivateContext deals with one buffer only, but with fbo
> we can have multiple simultaneous ones(GL_ARB_draw_buffers, or multiple
> render targets in d3d speak). In case of onscreen rendering only one render
> target may be active from the d3d side, and in case of back/aux and pbuffer
> offscreen rendering we're limited to one target from the opengl side.
>
> What has to be done in some way is to merge apply_fbo_state() with
> ActivateContext. My original idea was to select the primary target and the
> depthstencil buffer in ActivateContext similarly to the existing code, and
> have higher render targets set in the state manager. Unfortunately drivers do
> not like that, and we have to set all color and depth attachments of the fbo
> at once.

Thanks for the info.

 - Allan