Detect and use system fonts for extended language support

[Stoppedpuma]

Most non-english characters fail to be recognised and instead load a missing unicode. Checking for system installed fonts could be a work around to this.

[woelper]

This is rather easy to fix but will increase binary size. I am thinking of Japanese, Korean, Chinese, Arabic, are you missing anything in particular?

[Stoppedpuma]

Nothing in particular from my end, I think those four would be a good start and cover a good portion. Accented letters and cyrillics seem to be covered in my testing so this covers a good majority if the above are added as well.

On the binary size increasing part, is checking against system installed fonts not an option? This implementation could also be used in the future for text annotations.

[woelper]

There is an interesting thread here:
emilk/egui#1344
This is not directly possible with egui, so we'd have to balance either using system fonts and external libraries and deal with it on every platform against larger binary size.

[Stoppedpuma]

Lets go for your suggestion then!

Regarding interfacing with annotations:

It seems to be possible to manually load a system font according to a user in that thread:

let font = std::fs::read("c:/Windows/Fonts/msyh.ttc").unwrap();
fonts.font_data.insert(
    "my_font".to_owned(),
    egui::FontData::from_owned(font)
);

How we could handle text annotations in the future is we can either choose to have the option for the user to select a font, or just use the default font and exclude this option entirely. Assuming we want to allow users to have font options, this could be achieved by a fonts folder in the oculante directory so that it's portable and can be chosen in a drop down, "exposing" the above to the user. UX wise this also allows remembering the last font used state which may be something desired?

Slightly off-topic but perhaps we use the "fonts" folder idea with favourite images as well by creating a copy or if possible a hardlink? This should definitely be a toggle though since it can take up a lot more storage than a few fonts, and some may not be using oculante portably.

[Stoppedpuma]

Related to #603, should be closed when addressed.