[cairo] Difference in Cairo and Qt4 adjacent polygon rendering

Emmanuel Pacaud emmanuel.pacaud at lapp.in2p3.fr
Fri May 1 10:27:32 PDT 2009


Le vendredi 01 mai 2009 à 12:04 -0400, Hezekiah M. Carty a écrit :
> To put it simply, the various Cairo-based vector output formats (PDF,
> PS, ...) leave seams between adjacent polygons when viewed with
> Evince.  The Qt4-based outputs do not have these seams, even when
> viewed with Evince (see the above page for an example).  Both the
> Cairo and Qt4 rendering devices in PLplot are provided with the same
> input data and, as far as I can tell, they follow similar paths to
> produce the final result.
> Can anyone here provide some insight on this issue?  I see some
> previous discussions about similar trouble in the past (see [1]
> below), but none of the suggested answers seem to work for all cases.
> The fact that Qt4 is able to produce adjacent, non-square polygons
> which render cleanly in non-Qt4 viewers seems to indicate that there
> is some hope for this working in Cairo as well.

I have opened the files with inkscape (using pdf import), and there's a
difference in the two files that explains the visual difference when
viewed with evince: in the qt output, the polygon are not only filled,
but also stroked, which is not the case in the cairo output. The stroke
makes the polygons intersect and then suppress the seams.


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