[PATCH] wined3d: Avoid crash in swapchain_gl_present() if context could not be acquired.

[Paul Gofman]

On 11/14/19 18:23, Henri Verbeet wrote:
>
>> But the application is trying to present a swapchain into the window it
>> specified, the resource is onscreen (if we imagine that it is going to
>> draw something in some other case with a visible window, as here the
>> window is 1x1 and invisible). Does it make sense if we create another
>> invisible window instead and present something to the drawable obtained
>> from it?
>>
> Somewhat, in the sense that it gives us the option of using e.g.
> (gdi32) BitBlt() to still get the contents into the target window, if
> we really needed to.
>
> That isn't entirely the point though. Part of the issue is that the
> behaviour for creating a new context should be consistent with the
> behaviour for reusing an existing one. Another part is that for better
> or worse, the model we currently have is that provided OpenGL works at
> all, context_acquire() isn't supposed to fail. It may make sense to
> rethink that, but we have a lot more context_acquire() calls besides
> the one in swapchain_gl_present().
>
> The background is that the target window can go away at any given
> point, and D3D is supposed to keep working when that happens. Modern
> versions of OpenGL/GLX can make a context current without a drawable,
> but originally the drawable was required. Provided FBOs are available
> current wined3d always renders offscreen and only needs an onscreen
> context for Present(), but in the past that was not the case either.
> (I.e., think Opengl 1.x or 2.x and "backbuffer" ORM.)

Thanks for the explanation, I see now.

So I will make wined3d_context_gl_init() create backup context as well
if it fails to set pixel format (and maybe as well if wglCreateContext()
fails?).