Fade in the thumbnails when they are generated
Submitted by Jeff F.T.
Assigned to Jeff F.T.
If the thumbnails for the video clips in the timeline are not available, they are generated and this takes time. Fading a thumbnail in when its generation finishes, instead of showing it right away helps a lot mitigate the temporal perception of slowness in generating them.
See [[ https://github.com/pitivi/pitivi/blob/master/pitivi/timeline/previewers.py | timeline/previewers.py ]].