Would it be possible to set the default linecap and linejoin behavior in Painter or in PdfDraw?
In pdf the operators J and j handle this. Example:
page << "1 j\n"; // Sets round join
How is something "default" if you set it?
Other than that, I believe that defaults for PDF and Painter are the same.
That said, one lacking bridge code is direct connection between Painter and PDF - in reality, it should be easily possible to make PdfPainter - and SvgPainter too - as provided drawing capabilities are almost the same.