If id == 0, then we should grab the specified rect from the screen.
To do that, find all windows intersecting with the screen geometry, and
compose their backing store images into a screen-size pixmap.
Otherwise, find the respective backing store and grab only that.
Remove the old code respecting the desktop widget, which is no longer a
thing in Qt 6. The code was also wrongly grabbing only the first
containing - not intersecting - window's backing store into the screen
pixmap.
Enable the QScreen::grabImage test for the offscreen platform, where it
now passes.
Task-number: QTBUG-99962
Change-Id: I16eca7b082d65095a62c73624f86a4423e997a7a
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
8359e44324