Windows automatically disables DWM for opengl windows that have the
exact dimensions of the primary screen. This causes numerous issues,
such as menus and popups not showing up, and alt+tab misbehavior.
Adding a one pixel border via WS_BORDER solves all of these issues.
This is done by a QWindowsWindowFunctions to make it opt-in as turning
it on can cause an unwanted change in the look of the window so it is
up to the user to decide if they want this.
[ChangeLog][Platform Specific Changes][Windows] Add a function to
QWindowsWindowFunctions to enable working around a limitation with
showing other top level windows when showing a fullscreen OpenGL based
window.
Task-number: QTBUG-41309
Task-number: QTBUG-41883
Task-number: QTBUG-42410
Change-Id: I8c5c785f5024737cd034b2b703671632a8102700
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
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