Scroll-while-drawing

[dgsachs@…]

A common idiom on computer touchpads is that hitting the edge of a window while selecting or dragging objects causes the window to scroll.

I think that this idiom would be useful in Instaviz as well. If we want to connect two nodes on a large graph, and I know the second one lies just off my viewport, I should be able to just connect them without zooming out.

There's no risk of confusion between the scroll and connect operations in this case, *and* it also allows scrolling with one finger unambiguously: just start to make a line, and "cancel" the connect operation by releasing when no other node is highlighted!

Obviously two-finger scrolling should be retained (it's a bit easier to control since the action will be direct and not indirect), but I think that permitting the connect operation to scroll will improve UI responsiveness quite a bit.

[glen.low@…]

Good idea. I'm thinking of a hot zone several pixels thick around the edge of the screen, where if you sketch into that area and hold for 1/2 second, the auto-scrolling features switches on and any drags scroll based on a tangent from the start point and current point. The hold is important to avoid disturbing users who had meant to sketch and not scroll.

[glenlow]

(In [142]) Added autoscrolling while sketching to the screen edge (fix #21).