QT_SCREEN_SCALE_FACTORS is in many cases set on behalf of the user,
instead of by the user, so we should apply the standard app
scale factor policies to it, instead of interpreting it
as a user override.
Specifically, make it subject to the rounding policy set by
QGuiApplication::setHighDpiScaleFactorRoundingPolicy(). This
means that applications which support integer scale factors
only will see integers only, also when QT_SCREEN_SCALE_FACTORS
specifies a fractional factor.
Users who want to override can set
QT_SCALE_FACTOR_ROUNDING_POLICY=PassThrough
to restore the default Qt rounding behavior.
[ChangeLog][QtGui] The high-DPI scale factor rounding policy (settable with
QGuiApplication::setHighDpiScaleFactorRoundingPolicy() or
QT_SCALE_FACTOR_ROUNDING_POLICY) now applies to scale factors set
with QT_SCREEN_SCALE_FACTORS.
Fixes: QTBUG-95930
Fixes: QTBUG-99546
Change-Id: I936e96671fe2a0a43c3e8129f0768875cb011103
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
9a39b3c796