GitLab

Signed-off-by: Yikai Lu <luyikei.qmltu@gmail.com>

I don't know why this happend... So shameful

Since its undostack is already exposed, there is no need it to be private.

Because spaces will be automatically inserted

Signed-off-by: Hugo Beauzée-Luyssen <hugo@beauzee.fr>

- Add missing headers
- Let the framework handle background generation of the thumbnails
- Let the framework handle the caching
- Use Image instead of Pixmap, since the later might not be usable
outside of UI thread

We now duplicate the clips when resizing, otherwise multiple clips would
share the same begin/end during the resize

This was rejecting a move from a track to another one if the clip was
moved to the exact same position