decelerated pinch zooming on iOS

[incanus]

Lower priority than #34, but Apple & Google do decelerated zoom coasting upon pinch release. Probably involves manual deceleration easing since UIScrollView doesn't do this.

[kkaefer]

Does the gesture recognizer do this? When I looked at the API, there was something like that in there.

[incanus]

No, it does on pan, but not on zoom. There is a bouncing effect on either pan or pinch, but this is just when hitting the limits.

The basic idea of deceleration over in #34 is described here: http://www.odysseyinc.com/blog/rotating-opengl-view-touch-gestures/ The offsets on the scroll view are used to drive a CADisplayLink, which hits the render() call during its own deceleration. I've had good luck with it before e.g. https://dl.dropboxusercontent.com/u/575564/ismapview.mp4 which is a map view I made in raw OpenGL ES which renders raster tiles as textures.

The problem is the zoom pinch gesture does not have any deceleration in UIScrollView.

[incanus]

We should use -[UIPinchGestureRecognizer velocity] for this with an easing animation.

[incanus]

Making this even lower priority, this sucks hard when you can't cancel other (i.e. pan) animations.

[incanus]

Cancel is now in via 28ee596

[incanus]

Implememented similarly to decelerated panning. It's hard to trigger since simultaneous pan/rotates can cancel the animation, but it's there in the unlikely event that you merely only pinch. May revisit if this needs tuning up once performance is better.