Custom fonts have really large text boxes when selecting

[cyphar]

When creating a PDF using printpdf, I've noticed that with custom fonts (specifically Roboto Slab and B612 Mono), when you try to select text in a PDF viewer the selection will be much taller than the text and will overlap adjacent lines (rendering them invisible). If I use the built-in courier fonts with exactly the same text settings, the problem goes away. Here's a screenshot of the issue in Evince:

This is most notable when opening the PDF in Evince. In Firefox and Chrome the selected text is the right height. You can get a copy of an example PDF with this problem here.

[fschutt]

The "problem" with those fonts is that the unitsPerEm field is set to 2000 instead of the default 1000 and Evince is the only PDF viewer that doesn't respect that.

I can work around it by dividing the ascender / descender by 2.0, but then the text appears "spaced out", because the glyph widths still expect 2000 units per em:

I also need to debug why the ascender / descender doesn't use the sTypoMetrics field as it should. The fix is to scale the ascender / descender AND the glyph widths to 1000em and also to submit a bug report to Evince.

[seijikun]

Same problem with Okular. I think both depend on Poppler for pdf parsing/rendering, so if that's really a viewer bug, it might be located there.
I opened a bug for Okular: https://bugs.kde.org/show_bug.cgi?id=470091