This is a new try of mciqtz32's video window patch.
Comparing to the previous !370, I added a lot of tests regarding the video window behavior.
Some portion of the previous patch are dropped to avoid complexity, I'll add that part later.
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v4: mciqtz32: Show the default video window when switching from another one.
mciqtz32: Hide the default video window when switching to another one.
mciqtz32: Reset the video size when changing video destination.
mciqtz32: Fix MCI_DGV_WHERE_WINDOW behavior.
mciqtz32: Correct video window behavior by creating default window.
winmm/tests: Add tests for destination of video window.
winmm/tests: Add tests for dimensions of video window.
winmm/tests: Add tests for window style of video window.
mciqtz32: Don't hide video window when stopping.
winmm/tests: Add tests for visibility of video window.
https://gitlab.winehq.org/wine/wine/-/merge_requests/557