make soundfont source configurable

[fnordomat]

I noticed that the gm_* sounds do not work when I run strudel locally and offline, without getting the soundfont data from the web.

The reason is that the soundfonts package still has a hard-coded URL where the soundfont data is fetched.

Here's the corresponding line with the TODO:

https://github.com/tidalcycles/strudel/blame/7839d6b4bfb2e39cc54d65a5172c1886def71616/packages/soundfonts/fontloader.mjs#L18C14-L18C48

There should be a way to specify the soundfont base URL as a global configuration constant.

[felixroos]

good point. maybe something like:

soundfontUrl('https://felixroos.github.io') // default
soundfontUrl('http://localhost:6543') // localhost

then the final url would be ${soundfontUrl}/webaudiofontdata/sound/${name}.js;.

To run locally, a fork of webaudiofontdata needs to be served on localhost i guess.

As a longer term goal I think it would be cool if superdough had a more integrated approach to soundfont loading.
I've started working on this here, but nothing usable yet.

[fnordomat]

That sounds good.

For the short term approach, I tried to implement this:

#1040