I'm trying to implement KDE4.4 oxygen style for XFWM4, but currently i can only use solid color, because radial gradient is impossible to implement - lack of stretching is the greatest problem, and the fact that fragments (1-5) sizes are defined by title text size makes it even worse.
I'd like to have a way to use single stretchable background image.
As i have found, Oxygen style can't be implemented via images. There needs to exist a theming engine API for this.
I have also had difficulty (it's impossible) porting themes to xfwm4 due to a lack of title image stretching, for example Reluna 3 by bant. A large number of windows and KDE themes are unportable due to this limitation, making it harder to reach for the low-hanging fruit when theming XFCE. The minimum fix for this would be allowing some (maybe just the center one) of the titlebar images to be smoothly scaled rather than tiled.