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

[Henri Verbeet]

On Thu, 14 Nov 2019 at 15:47, Paul Gofman <gofmanp at gmail.com> wrote:
> On 11/13/19 21:16, Paul Gofman wrote:
> > Yes, the window handle is actually valid, as well as dc. Yet
> > wined3d_context_gl_set_pixel_format() called from
> > wined3d_context_gl_init() fails. The failure comes from winex11.drv,
> > create_gl_drawable() fails through create_client_window(), which in turn
> > gets NULL get_win_data() and refuses to create the data here. This is
> > some (WS_POPUP | WS_SYSMENU) window created with 1x1 size which never
> > changes, and looks like it never get shown. It does not look like the
> > application is serious about trying to display something with it, as
> > nothing seems to be missing on the display, yet it create d3d11 device
> > there (while the game is mostly d3d9), draws a few frames and gives up.
> > Do you think that wined3d should try to work around any possible reason
> > when display driver fails to create opengl visual or can't set pixel
> > format for some other reason? If the context is not supposed to be NULL
> > in swapchain present under normal circumnstances, maybe we put ERR()
> > there for the time being?
> >
> A bit of more details on this. The swapchain for which
> swapchain_gl_present() fails is not a main device swapchain. The main
> device swapchain is created for the other window and is fine. That
> failing swapchain is created from dxgi factory
> (dxgi_factory_CreateSwapChain).
>
> The creation of the swapchain succeeds, wined3d does not try to create a
> GL context during that.
>
> Then it gets swapchain backbuffer (dxgi d3d11_swapchain_GetBuffer) and
> renders something to this backbuffer as RTV.
>
> Then it calls d3d11_swapchain_Present() for this swapchain, and here is
> when it tries to create GL context for the first time and fails in
> SetPixelFormat.
>
I think that makes sense, although it's still not entirely clear to me
why setting the pixel format fails. As for fixing the issue,
wined3d_context_gl_init() should probably take the same approach as
wined3d_context_gl_set_gl_context(), or perhaps things can be
reordered in a way that wined3d_context_gl_init() can simply call
wined3d_context_gl_set_gl_context().