The color/pattern is given through the configuration file, and updating due to changes of the configuration file works perfectly. A simple user-interface to use this will be added to the panel configuration.
If you want to try this out, put into the [Theme] section of your plasmarc file:
frameBackgroundColor=#aacc00 (Your picked color)
frameBackgroundColorAlpha=120 (Alpha value for the color, between 0 and 255, 0=invisible, 255=opaque)
frameBackgroundPattern=/path/to/image
frameBackgroundPatternAlpha=255 (Alpha value for the pattern, as above)
The color is painted first, then the pattern. They are painted into the mask defined by the theme, so this only works nicely with themes that supply proper masks.
svn path=/trunk/KDE/kdelibs/; revision=961915
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