feat: add inkml parser and writer

[Doublonmousse]

Related to #744 (import of selected onenote strokes, but exclusive to that. No text nor images are read).

As I'm on windows, I'm using #1282 for now.
The parser/writer crate is on a separate repository here https://github.com/Doublonmousse/writer_reader_inkml

Export and import are supported (from the clipboard).

• I think it would make sense to move some of the import code inside the engine (conversion from inkml to stroke ?)
• The export part is only for brush strokes (I could extend it to shapes with lines being the easiest to do, and other shapes would have to be discretized)
• I'm using the windows equivalent of the mime type for the inkml clipboard export part
• The crate still needs some polishing (better error message and removing some potentially panic inducing unwrap with error propagation instead).

I've encountered a weird behavior with clipboards in gtk and windows (that ofc I can't reproduce today ...). Copying ink content then an image from a source application wouldn't work as somehow gtk would think the inkml format was still present before failing with a gio quark error.

[Doublonmousse]

It's starting to look somewhat reasonable. I'm still not fully sure the modifications are done in the right place.

And I've encountered again a gtk bug with the clipboard (this time I could reproduce)
Recording 2024-12-30 171734_compress.webm

56.954780700s ERROR rnote::appwindow::actions: Failed to read clipboard data while pasting as inkml, Err: Error { domain: g-io-error-quark, code: 0, message: "Cannot get clipboard data. No compatible transfer format found." }

I wonder if it's possible to refactor the code to try the next mimetype if the first one failed. Though that's ultimately a workaround for a gtk/gio bug (I'll probably try to open a bug report on the gtk or gio gitlab later)

Upstream tracking issue here : https://gitlab.gnome.org/GNOME/gtk/-/issues/7233

[Doublonmousse]

The issue I had was fixed upstream, so this should be working for gtk 4.20

[Doublonmousse]

One passing though on conversions: I feel like an interface/trait for general conversion could be done.

Also, if it'd be possible to have a minimal rnote library that's just big enough to load rnote files but also create elements and push to the store then save to a rnote file that'd facilitate how to do conversions (and also embed the reader in other contexts)

[Doublonmousse]

Implemented shapes export ("rasterized" to lines) using the outline_path method + a couple of fixes
I need to retest on windows to verify everything is fine with import/export from/to onenote/journal/office.

I'm also encountering some weird behavior for rendering. When doing a roundtrip (copy from rnote, then modify the clipboard to only keep the inkml content then pasting again), the arrow should not display correctly (as I'm currently doing it in one stroke vs taking into account the MoveTo as an indication to do a new stroke) but it does

If I remove the start,

A pasted polygon (so represented as a brushstroke here !) can "lose" a side when seen from further away

[Doublonmousse]

Re tested on windows with journal/onenote/word and everything works as expected (including shapes).

Export to journal doesn't take the inkml format but prefers the png (edit: retested and it outputs inkml but the reverse is false, only ISF would work on implrt).

Now there may also be some annoyances here (if I prefer inkml over other clipboard format, I may miss on images ..). Though apart from a copy as/paste as function I'm not sure it can be fixed