[LGM2009] slow / laggy dragging : do not update the preview until drag is released
Submitted by Jeff F.T.
Assigned to Jeff F.T.
If the timeline playhead is currently over a clip and you try to move this clip, or if you move a clip into an area where the playhead is, you will experience lag/jerky movement, which hurts precision editing a lot.
This is most likely because it tries to update the preview image with the playhead's position all the time.
My proposal would be for this behavior to be disabled when a drag operation is underway, and only update the preview when the drag is released.
Imported from https://bugzilla.gnome.org/show_bug.cgi?id=579238