Building for WebAssembly

[waywardmonkeys]

Building for WebAssembly targets with default features (read: system) is broken as there isn't an implementation for WebAssembly.

• Should crates using fontique build with no-default-features and then enable system on all but WebAssembly?
• Should the null backend be enabled for WebAssembly for the system feature? (Seems like it goes against the idea of a system feature.)
• Should system not be enabled by default and let consuming crates enable it?
• Something else?

[xorgy]

system is the main point of fontique, so it being default makes sense, but that leads to the issue you describe.
There is also the issue of how to make a useful collection at all in WebAssembly, which I think would probably involve a considerable amount of support from the JavaScript side, or inlining a font into the wasm module (not necessarily the greatest solution either).

[waywardmonkeys]

There is https://developer.mozilla.org/en-US/docs/Web/API/Local_Font_Access_API (only currently supported in Chrome and Edge 103 and later, but not Chrome for Android) ... but that would require having async APIs for WebAssembly.

[xorgy]

Well, may not require async APIs for wasm, but rather that the loader take care of that stuff before starting the module (or that calls for the system fonts involve waiting). I was not aware that the Local Fonts API had rolled out to any stable browsers!

[xorgy]

Looking into this, apparently it gives you the font data as Blob, which unfortunately can not be mapped zero-copy into wasm memory (at least, not explicitly); so probably the useful way to implement this would be some sort of limited font library selected by the host and copied into the wasm memory.

[xorgy]

Looking into it further, the Local Font Access API has to prompt for permission in a browser, and the message used is something about ‘creating high fidelity content’. If you're building something other than a graphics editor or a tech demo, then presumably a lot of people will click block on this and break your app.

[torokati44]

FWIW: Aside from Chrome, the promise of this working well in either Firefox or Safari is not particularly rosy: mozilla/standards-positions#401 (comment)