Jog/shuttle using the mouse
@jeff
Submitted by Jeff F.T.
Description
Jog/shuttle: Advanced navigation features that allows user to quickly locate very precise edit points in pipelines. Ideally these features would be always accessible via an external control interface (called a "jog/shuttle wheel" on professional setups, see https://en.wikipedia.org/wiki/Jog_dial for more info). Since most users won't have this it can be approximated with the mouse.
The jog/shuttle mode could be activated by pressing a mouse button.
When the mouse cursor goes out of a small "deadband", left or right, the playhead starts moving in that direction.
The speed of the playhead is calculated depending on how far the mouse cursor is from the initial mouse cursor position and depending on the zoom level.
The playback head should be kept in view (a feature conspicuously absent from some major commercial products).
Getting out of the jog/shuttle mode can be done for example by clicking ESC, Space or the same mouse button used to activate it.
#1310
Depends onImported from https://bugzilla.gnome.org/show_bug.cgi?id=572432