Created attachment 133666 [details]
pdf file to trigger the bug
The Arthur render backend implements the 'Miter' line join style incorrectly. You can see this with the attached test file. It contains a polygon with two corners positioned such that the miter limit is exceeded. The pdf standard requires that in such a case, the miter join is converted to a bevel join:
The Arthur backend, however, simply shortens the miter a little bit. This results in the spike that can be seen on the screenshot.
Created attachment 133667 [details]
The file as rendered by the Splash backend
Created attachment 133668 [details]
The file as rendered by the Arthur backend
The fix is to use Qt::SvgMiterJoin instead of Qt::MiterJoin. It is recommended in
and does indeed fix the problem. I'll attach a patch.
Created attachment 133669 [details] [review]
Patch to use the correct join style