Doc: a QScreen can be a placeholder if there are no screens attached

As of change a094af001795c9651b299d700a992150d1aba33a, X11 now joins
other platforms in having a fake screen if no physical screens are
attached, rather than ever allowing QGuiApplication::screens() to
return an empty list or QGuiApplication::primaryScreen() to return
null.  This is more consistent across platforms and helps to prevent
bugs in applications which want to use QScreen in some context but
fail to check whether it exists.

[ChangeLog][X11] In case there are no physical screens attached,
QGuiApplication::screens() and QGuiApplication::primaryScreen() will
return a placeholder QScreen object.

Task-number: QTBUG-42985
Change-Id: I0f58afbfe2a034fb9e872a5d1dbdabad2c7dbf9e
Reviewed-by: Błażej Szczygieł <spaz16@wp.pl>
Reviewed-by: Paul Olav Tvete <paul.tvete@theqtcompany.com>

0 files changed, 0 insertions, 0 deletions