Due to an XCB library change, QXcbBackingStore::toImage() cannot be
safely assumed to return an image identical to QWidget::grab().
The test functions fastMove(), moveAccross() and moveInOutOverlapped()
relied on QXcbBackingStore::toImage() and failed.
They were backlisted on Linux/XCB.
This patch obtains a screen shot instead of an image from the backing
store on XCB platforms. It processes events until the screen shot
matches QWidget::grab(). It makes the test fail only if the comparison
times out.
The patch also removes the BLACKLIST file, containing only the test
functions mentioned above.
Fixes: QTBUG-109036
Pick-to: 6.5 6.4
Change-Id: I26dd5b89dc62b313db066a285f6ad7d4d92baaf2
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
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