A font is processed by software, one part of the font rendering stack is converting a string into glyphs and their positions, other part is rasterizing glyphs into bitmap. In this case one library from the stack, HarfBuzz [1], got the support for, I assume, an extension to OpenType format, that allows to embed an extra section into the file [2]. So HarfBuzz can open these special OpenType files and make run wasm embedded into them. Which means software based on it, like Chrome browser or Android, will also be open these font files, but Windows likely not.
- [1] https://en.wikipedia.org/wiki/HarfBuzz - [2] https://www.phoronix.com/news/HarfBuzz-8.0