[KCM] Limit scale factor increment to 6.25% on X11
Summary:
Because of the nature of floating point math and various Qt and X11 bugs, limiting the
scale factor increment to 0.0625 (6.25% in percentage form) will improve the display in
many apps.
For more information, see the discussions in https://bugreports.qt.io/browse/QTBUG-66036 and
the following bug reports:
CCBUG: 412447
CCBUG: 390451
CCBUG: 373232
Depends on D24370
Depends on D24371
Test Plan:
Reviewers: Plasma, romangg, mart
Reviewed By: Plasma, romangg, mart
Subscribers: cullmann, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D24373