This partially reverts 51ada7734a
because it's necessary to keep some scenarios with vnc and
remote X servers working. When an application is starting,
if we don't find the xrandr outputs but we know the dimensions
of the screen, we should still be able to put windows onto that
screen; but when we already had known xrandr outputs and then they
were removed, that's the case where we want to stop rendering
(and have no screen instances) until the screen(s) are reattached.
Task-number: QTBUG-31389
Task-number: QTBUG-40174
Task-number: QTBUG-42985
Change-Id: I13d0996ba6ece78c4ebcd2c3a59f1617c1c7f0fa
Reviewed-by: Uli Schlachter <psychon@znc.in>
Reviewed-by: Gatis Paeglis <gatis.paeglis@digia.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>
ebdf991660