Question about XRender specification

Carl Worth cworth at
Mon Apr 7 12:02:23 PDT 2008

On Mon, 7 Apr 2008 20:54:07 +0200, "Clemens Eisserer" wrote:
> I have some problems understanding the following behaviour:

You don't understand what this paragraph is specifying? Or you don't
understand why you appear to be getting results that don't seem to
match it?

> > Abutting edges must match precisely.  When specifying two polygons
> > abutting along a common edge, if that edge is specified with the
> > same coordinates in each polygon then the sum of alpha values for
> > pixels inside the union of the two polygons must be precisely one.
> When I have two trapezoids, where the first ends at 100/90  and the
> second begins at 100/90 (speaking about the horizontal edges) -
> shouldn't both accumulate to one large and seamless trap. If not,
> whats wrong with my testcase?

What does "100/90" mean? (If that matters.)

Yes, two trapezoids with a common edge should accumulate
seamlessly. And yes, that's the intent of the paragraph you quoted.

So given that, I don't know what you're actually seeing, (presumably
something different). Could you please provide the test case and
results so that we can investigate the issue?

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