This feature was already available in the Qt3 version: 
https://forum.kde.org/viewtopic.php?f=156&t=126095#p333740

Yes, that's right. When Krita 2.0 was refactored, we had to disable all tools and port them one by one. The original author had disappeared and when the dust settled these tools still hadn't been ported. We've had one or two requests for them since, but it's not exactly super-high on the todo for now. Though it should be done at one point, of course.

I found a special GIMP plug in, which does the job really great, it might be possible to reuse the code:

https://youtu.be/fzMSXHVkkGw

https://github.com/bootchk/resynthesizer

Oh sorry, this is something completely different.

Restoring the old tool to basic functionality was fairly straightforward. There is now a patch to add a basic version of the tool.  Unfortunately the existing algorithm for identifying the magnet boundary is very crude and will have to be redesigned even more completely than the tool itself. 

https://phabricator.kde.org/T556
https://phabricator.kde.org/D241

Thanks a lot, this sounds awesome, i hope it becomes easy to use in the next months. :)

WISHGROUP: Big Projects

Seems we ran into trouble there :-(

I'll take a look at this again after Dmitry writes the lazy brush, since it would be using a lot of the same infrastructure.

I think is already implemented, right?

It isn't.

Dmitry did finish the lazy brush but I haven't been able to come back to the magnetic lasso and I do not currently have plans to work on it anymore. The code to restore the janky original lasso is still available on Phabricator, if someone wants to write an A* algorithm for Krita you can pull the patch yourself and play around with it. Looking at Dmitry's code for the watershed algorithm should be useful though.

https://phabricator.kde.org/T556
https://phabricator.kde.org/D241

Completed, :)