This replaces the old backend that exclusively used EGL windowing with
one that can also use ANGLE's ability to render to directly to a
texture. The advantage of this is that it allows mpv to create the swap
chain itself and this allows mpv to use a flip-mode swap chain on a HWND
(which avoids problems with DirectComposition) and to use a longer swap
chain that has six backbuffers by default (which reportedly fixes
problems with rendering 24fps video on 24Hz monitors.)
Also, "screenshot window" should now work on DXGI 1.2 and up (Windows 8
and up.)
This is useful in particular for GetLastError, unfortunately, it's stil pretty
dumb with regards to WASAPI or D3D specific errors, so keep the
hresult_to_string switch.
Note that hresult_to_str() (coming from wasapi_explain_err()) is mostly
wasapi-specific, but since HRESULT error codes are unique, it can be
extended for any other use.
James Ross-Gowan
Kevin Mitchell
wm4