When the KDE theme gets changed programatically or by the user in KDE
settings, Qt applications were not notified during run time.
The KDE theme was read during startup only, when the QApplication's
palette was constructed.
This patch implements a DBus connection to the SettingChanged signal.
QKdeTheme is notified about KDE theme changes, which trigger an
application palette reconstruction and all subsequent QEvents.
The implementation reacts to changes the in KDE settings "widgetStyle"
and "ColorTheme". The application palette is updated only if the
underlying settings change results in a palette modification.
Fixes: QTBUG-103093
Pick-to: 6.4 6.3 6.2
Change-Id: If0ec0f0ba515ef3dcf9924283d3a818ac7d24a7b
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
223fdc7d52