[optimisation] Block signals from timeline while doing complex changes
@bilboed
Submitted by Edward Hervey Assigned to Brandon Lewis @brandon_lewis
Description
When doing a SimpleTimeline move, several sources are being moved around, priorities changed, etc....
Currently, whenever a single property changes, the UI is updated, which is very cpu intensive.
There should be a way to block all signal emissions from gnonlin to be forwarded from pitivi.timeline to the UI, and a way to then emit all those signals at once.
Imported from https://bugzilla.gnome.org/show_bug.cgi?id=396803