QT_SCREEN_SCALE_FACTORS in many cases set on behalf of the user,
instead of by the user, so we should make it less sharp and more
in line with standard high-dpi configuration.
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.
Pick-to: 6.4
Fixes: QTBUG-95930
Fixes: QTBUG-99546
Change-Id: Ibb0aa5cb9d3a356d33429d0efe69d984b2530728
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
1c0a56a2f3