Bug 358780

The "expand clip" functionality is simply great, it adds so much value to Kdenlive. However, my impression is that it needs some polish in order to avoid the false impression that it doesn't work at all. In particular, I miss these two these two aspects:

1. error feedback when expand clip is unable to expand a clip -- currently, there is no error feedback at all and this left me often wondering what went wrong.

2. (in) progress feedback while MLT crunches on more demanding clips -- currently, there is no feedback at all, so the user doesn't know whether Kdenlive is still working. Especially as there is no error feedback either, Kdenlive leaves users in the dark as to what is happening.

For instance, often Kdenlive is unable to expand a clip -- one cause for expansion not working may be that the required tracks are already occupied by clips at the range covered by the expanding clip. However, as there is no feedback the user has no way to understand what to do when expansion fails.

I only found out by trial and error that library playlist clips usually expand correctly when I put them to the end of the project timeline, a region where there is enough space also track-wise to expand.

In addition, Kdenlive doesn't report back when there are not enough tracks to expand a clip. Of course, it would be great if Kdenlive then could ask back to add enough tracks and after confirmation then do the necessary changes and expansion.

Reproducible: Always