[GRASS5] [bug #242] (grass) R_polygon_abs() seems to ignore islands

[Glynn Clements]

Eric G. Miller wrote:

> > XDRIVER24 uses XFillPolygon's "Complex" mode, which should handle
> > self-intersecting polygons. However, there is a choice of two filling
> > rules: EvenOdd and WindingRule. From the XChangeGC manpage:
> 
> Yes, I played with them, they aren't the problem.
> 
> Problem is, there's no protocol for drawing polygons with holes.  That
> is, the inner "holes" of the polygon should mask out the drawing of the
> outer polygon.  I fooled around with d.area to create something of a
> work around, but it isn't a very good implementation.  This capability
> needs to exist in the drivers so they can implement it however is best
> for their "device".  Built vector areas have the holes identified, so
> it's at least partially a matter of passing this data to the driver for
> appropriate behavior.

So, the issue is that the drivers can only draw "polygons", leaving no
simple way to fill arbitrary "paths" like PostScript can?

In which case, this isn't likely to get fixed any time soon; even
lifting Mesa's GLU-1.2 tesselator won't help. We would need the
equivalent of the GLU-1.3 tesselator; given that Mesa's current stance
is "use SGI's GLU library", I'm not expecting a GPL'd version to
become available any time soon.

-- 
Glynn Clements <glynn.clements at virgin.net>

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