GObject::dispose method can be called multiple times. As win32 d3d11window
has an internal thread and because GObject::dispose method could be called from the
thread, it might cause problems such as trying to join self-thread
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1299>
* Remove redundant variables for width/height and par from GstD3D11Window.
GstVideoInfo holds all the values.
* Don't need to pass par to gst_d3d11_window_prepare().
It will be parsed from caps again
* Remove duplicated math
Fixing regression of the commit 9dada90108
DXGI_SWAP_EFFECT_DISCARD cannot be used with dirty rect drawing feature
of IDXGISwapChain1::Present().
Note that IDXGISwapChain1 interface is available on Platform Update for Windows 7
and DXGI_SWAP_EFFECT_FLIP_SEQUENTIAL is also the case.
Don't specify the resolution of backbuffer. Then dxgi will let us know the
actual client area. When upstream resolution is chagned, updating the size
of backbuffer without the consideration for client size would cause mismatch
between them.
