The implementation was already there, and handles theme changes at
runtime as well. However, it was disabled unless the QPA parameter
"darkmode" was set to either 1 (supporting only the frame) or 2 (the
Windows theme also supports dark mode when reading the palette).
With both Windows 10 and Windows 11 now having dark mode as a fully
supported feature that is easily accessible to end-users, we should
respect that setting by default.
So change the default: support both dark window frames and palette, and
let users turn this partially off by setting darkmode=1 or darkmode=0.
This does not mean accent colors etc are fully supported by the Windows
styles.
[ChangeLog][QtGui][Windows] Dark mode, both for the window frames and
for the palette, is now supported by default. It can be turned
off (partially or entirely) by setting the QPA parameter "darkmode=0"
(no dark mode support) or "darkmode=1" (darkmode support only for the
window frames).
Pick-to: 6.4
Fixes: QTBUG-72028
Change-Id: Ia55af101896c106cde21340b306aa81390e608a2
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
43ef22045c