for use in effects (and not only). Now a list of window quads (=window areas)
is created at the beginning of the paint pass, prepaint calls can modify
the split itself (i.e. divide it into more parts). The actual paint calls
can then modify these quads (i.e. transform their geometry). This will allow
better control of how the split is done and also allow painting e.g. only
the decoration differently. Still work in progress, but it works.
Also pass data to prepaint functions in a struct, as there is
already quite a number of them.
svn path=/trunk/KDE/kdebase/workspace/; revision=684893
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