Is Canvas really suitable for PDFs ? Afaik it's immediate mode bitmap graphics - so PDFs would just be embedded bitmaps ?

We do indeed generate vector PDFs, not embedded bitmaps.

Our graphics engine works with Canvas API instructions — like "draw a line from point (A,B) to (C,D)." This API is small enough and low-level enough that it can also generate pristine vector output.

That's in fact one of the features of Skia Canvas (vector output in PDF and SVG).

Ah nice didn't know it had a PDF backend - that sounds perfect for this use case.

Curious: What other libs are you using for the PDF generation?

On a related note, I once used puppeteer and headless chrome in a docker image to generate PDF manuals from our web page documentation using the print to PDF feature of headless chrome.

I am not sure if it would be viable to use for thousands of PDF generation per minute but it worked great. I wasted a lot of time trying to find a good lib for HTML->PDF and they all kinda sucked in different ways. The only downside is that the chrome PDF api doesn't have a way to generate a table of contents with page numbers.

I have a soundslice account that I use infrequently. It's pretty nice. Thanks for building it and making it available.

When you mentioned Soundslice I recognized your name :) Your recording of Django's Tiger is what got me into Jazz. Small world!