I just finished an adaptation of your pdf generation code over to cogent core: cogentcore/core#1619 and discovered a couple of issues you probably want to fix in canvas:

writer.go:1343

	fs := []pdfDict{}  -> fs := pdfArray{}

the write function doesn't know how to write a []pdfDict{} and so this silently fails to write the fs when it is needed.

pdf.go:146, 189

			if style.FillRule == canvas.EvenOdd {
				r.w.Write([]byte("*"))
			}

there is no s* or S* defined in PDF, so these end up failing to render the stroke element (silently it seems).

I really appreciated your clever design (once I finally figured it out) for how to efficiently handle the peculiar demands of generating the pdf format -- much cleaner than the fpdf package which I also looked at.

I also implemented links to navigate to different parts of the document, and table-of-contents, so if you want to see how those work they are in https://github.com/cogentcore/core/blob/pdf/paint/pdf/links.go -- nav links took me a long time to figure out b/c the docs were really unclear to me -- have to put everything in a separate object basically.

The driving use-case for me is to generate PDF versions of my online publishing platform, e.g., https://compcogneuro.org/basal-ganglia -- you can click on the PDF button now and get a nicely formatted PDF version of the content. All in Go :)

Anyway, thanks again for all your great work on canvas!