Add text corresponding to layouted glyph

[LaurenzV]

What do you think of this? I basically adapted it from https://github.com/typst/typst/blob/105d7156f8f9d95e16b3eefdf0fa97e5be7fbe5b/crates/typst/src/layout/inline/shaping.rs#L729-L733

I also checked and I've managed to get copyable text to work (in svg2pdf), I also tried it with other scripts (like Arabic) and it seems to work!

[LaurenzV]

Umm... I have no idea why Qt is failing?

[RazrFalcon]

Yep, it's unrelated. I guess it fails to download the Qt version I need. Ignore it.

As for the patch, yes, Arabic/Hebrew is the first thing you should test. Zalgo as well.

I think the old code was able to get char by byte_idx, but not the whole string/cluster. Allocating the whole string for each span might be a bit expensive, but I guess it's fine for now. We could use Box<str> as an optimization here.

[LaurenzV]

Yup, Hebrew seems to work as well. Not so much for zalgo (as in, it renders correctly, but copy-pasting results in more or less garbage), but it also doesn't work when exporting the SVG to PDF via Chrome, so I don't think this is worth investigaging...

[RazrFalcon]

Thanks!