[Dev-luatex] Re: Font embedding and variable width fonts

Hi Patrick, On Wed, 2025-04-09 at 09:19 +0200, Patrick Gundlach wrote:

I am playing with variable fonts, and I can see that I can create font metrics with

font:set_variation(...)

so the shaper takes the new widths into account.

But writing this font into PDF has no visible effect. I assume the subsetter in LuaTeX does not take the variations into account.

You can use the (undocumented) "glyph_stream_provider" callback to write the correct data to the PDF file. If you're using luaotfload or ConTeXt, it handles the "glyph_stream_provider" for you, so you can just add the data for each character to "fonts.hashes.streams[].streams", which is an array indexed by the character index. You can use "glyph_stream_provider" for both CFF and TrueType-encoded characters; for type-3 encoded characters, you'll need to use mode 2 in the "provide_charproc_data" callback. I've only ever personally used "provide_charproc_data", so if I'm wrong on some of the details for "glyph_stream_provider", hopefully someone will correct me. Thanks, -- Max