Something weird is going on with trimming, undo, and redo

[TRA]

Steps to reproduce:

1. Launch Shotcut.
2. Open a video or image file.
3. Move a portion to it to the Timeline. Preferably, the start frame of the clip doesn’t match that of the original file.
4. Drag the clip to leave some empty space between the 00:00:00:00 mark and the left edge of the clip.
5. Move the left edge trim handle of the clip to trim it.
6. Press Ctrl+z or choose Undo from the menu to undo.
7. Press Ctrl+y or choose Redo from the menu to redo immediately afterward.
8. The trimming you made in 5) doesn’t get a redo.

There is some weirdness to the outcome in 8). They are not reproducible all the time:

• Sometimes, redoing does nothing and the clip length stays the same.
• Other times, redoing moves the clip as if it’s dragged.

After 8), I can’t drag the clip to close the empty space I’ve left at 4). Here are the two instances I wasn’t able to do it:

• There is only one clip, I trim it to shrink it instead of expand, and I try to close the empty space between the 00:00:00:00 mark and the clip.
• There are two clips, I trim the 2nd one to shrink it instead of expand, and I try to close the empty space between them.

Having another clip in front of the original clip doesn’t change the outcome as long as there is some empty space between them. If there is no empty space between them, the trimming gets redone.

Trimming with the right edge trim handle doesn’t cause this problem.

This happens in both single- and multi-track modes

An audio track exhibits the same problem.

a) Only tested in Windows 7 64bit.
b) This happens in 18.08.14 and 18.03.06. I’m presuming that all the versions between have the problem. In 18.03.06, the Redo shortcut is Ctrl+Shft+z instead of Ctrl+y.

[shotcut]

This is fixed for the next version 18.09.15