This is for SVG. Font-size is set in the style attribute, in pixels. Sometimes inherited from an ancestor tspan or text.

There are many sizes, and the output is proportionally correct (though 20px seems too small, they're always twice the size of 10px elements).

If the same SVG is converted to PDF with Inkscape, the fonts are all larger. That's what I was previously using, and is my baseline. Though, the SVGs when rendered on Firefox and other browsers certainly appear similar to this.

I suspect that the mistake is mine somewhere... so far I'm not doing anything fancy in my stylesheet (only setting page size and margin), do I need to do more than that? Perhaps there is a DPI setting that I've failed to give a sane value?

Any help appreciated.

If I recall correctly, pixel units in SVG are coming out equivalent to point units (pt) at present. Is your top-level document an SVG file, ie. it's not embedded within another XML or HTML document?

I'm starting to wonder if that was a boneheaded move on my part, there have been other issues as well unrelated to Prince. But I'm sort of invested at this point.

An explanation is fine, I was just worried I was screwing something up.

Just to be sure I understand, this issue is somewhere on the roadmap?

Or is it more of a "technically, that's what the spec says should happen"?

This is an issue that we need to tweak in Prince, and the solution is probably going to involve making the image resolution properties apply to SVG as well as bitmap images, allowing precise control of what 1px maps to on the page.

When an SVG image is included in a larger document, the width, height, and viewBox attributes are enough to determine the size of user / pixel units.