Proposal: Cairo-based, cross-desktop/toolkit theme engine API.

[Maksim Orlovich]

> I just want to note that Qt doesn't use Cairo but its own graphics engine,
> so this will introduce new dependencies for KDE themes (in addition to the
> indirection which is likely to come with non-native code and feature
> omissions compared to QStyle).

More importantly, a QStyle has to be able to draw on any QPainter.
Have fun getting cairo to do that.