Since 6.5.0, there is new infamous dark mode detection which automatically switches to dark palette when system "dark mode" is enabled, resulting in dark "Fusion" (and some others) style.

I do want to have some option to DISABLE this new behavior which actually breaks some older applications!

The culprit seems to be this piece of code from

https://github.com/qt/qtbase/blob/dev/src/gui/kernel/qplatformtheme.cpp#L358

Now, all old application newly compiled with Qt 6.5.0 switch to dark mode (if system is dark mode), which is not always desired.

I want to have some easy to set property (for example via "QStyleHintsPrivate::setColorScheme).

Also, add a property to "QStyle" (and subclasses) which says if the particular style actually supports "dark mode" or not as again - this is now hardcoded in styles and the information is impossible to have in apps. It was already there but was reverted out.

https://github.com/qt/qtbase/commit/c62c2aac752c6b63d5afd2f7a10dd9f43c99ae7b