Add fill tool

[MichaelBuessemeyer]

This PR adds a flood fill tool to the brush.

TODOS:

• use a better shortcut for the flood fill tool. -> replace with automatic brush
• test this with a fallback layer -> works
• integrate with undo redo

URL of deployed dev instance (used for testing):

• https://___.webknossos.xyz

Steps to test:

• Open chrome (firefox is not supported)
• Open a volume tracing and draw a circle in two strokes (not one as this would fill the whole inner area)
• Use "win/cmd" + left mouse inside the circle
• The area should be filled with the active cell id (should be pretty fast)

Issues:

• fixes Allow to split segments #4713

---

• Updated (unreleased) changelog
• [ ] Updated (unreleased) migration guide if applicable
• [ ] Updated documentation if applicable
• [ ] Adapted wk-connect if datastore API changes
• [ ] Needs datastore update after deployment
• Ready for review

[philippotto]

Very cool stuff!

Unfortunately, the feature didn't really work for me during testing. Not sure whether I produced some edge case (let me know if I should show it to you in a call), but I also left a comment regarding infinite loops which might be relevant?

Also, see my other feedback for improving code readability :)

[philippotto]

If I don't trigger the already mentioned edge case (which I seemed to have done all the time when first checking this out), this feature is a lot of fun :) Especially in combination with volume-undo. Very well done!! 🥇

[MichaelBuessemeyer]

@philippotto I just fixed the bug and applied your feedback as good as I could.

Could you please try out the newest version, once the CI has finished?

[philippotto]

Hmm, it crashed again for me. (probably I got served the old version) See this screenshot:

with the orange color, I initiated a flood fill at the bottom left corner (one can still see the hover where I clicked). z at 512

[philippotto]

Awesome, awesome, awesome 👍 I left some other minor feedback, but afterwards, this should be ready to get shipped 🚢

[MichaelBuessemeyer]

I think I just applied all of your feedback and tested the basic use cases. Everything should work.

@philippotto Could you please recheck this PR (after the CI is done) 🕺

[philippotto]

Top notch :)