[cairo] Variable line width

[dirk.schoenberger at sz-online.de]

> > Is it possible to draw paths or curves with variable width in Cairo?

> It's not currently possible. I think it would have some non-trivial
> impacts on some of the algorithms.

> > If not, don't You think it would be really useful?

> I think it would be really useful, and I've often been tempted to sit
> down and work out what it would take to do it.

Other libraries (I seem to remember Qt4's Arthur engine) expose such kind
of alogithms as a "path stroker". Such an algorithm is means as a
conversion from a path definition as a "series of strokes" to its "outline
form". The normal algorithms takes into account information like join and
cap styles, but I assume this could be extended to things like variable
line width.

Regards
Dirk