Change to time line interfaces

[theq629]

I'm finding that with the in-progress storyline view (issue #111) it is often difficult to zoom in to a small enough area on a plot that includes a long time domain. I think this is potentially an issue with the existing timeline view as well.

Therefore I would like to propose the following new interface for both:

• Dragging along the y-axis of the upper plot selects a new time range to zoom into. After ending the drag the zoom is applied immediate. The fact that the user can drag here is somehow indicated visually.
• There two new buttons above the upper plot, one to zoom out one level (undo the last zoom) and one to zoom out all the way.
• The lower plot can be used to move the view area, but not to resize it (otherwise it's impossible to move a small view area).

Additionally, for the timeline view, dragging inside the upper plot selects the constraint. This makes the timeline more consistent with the other views, where the view area and the constraint selection are decoupled.

For the storyline view, the change for this would be done after the initial merge.

[anoopsarkar]

Can we simply move left and right using a mouse scroll on the top pane of the timeline or storyline view.

[theq629]

We could do that too, but I'm not sure it would be as convenient. I find I do like the drag to scroll in the current timeline and storyline.