Most of the time NSScrollView’s animated scrolling Just Works. But I’m running
into a frustrating edge case where the exact same scroll code animates in
response to one UI event but not another.
Here’s the deal: In my app the left and right arrow keys jump to the
previous/next track marker in an audio timeline view. To do this I compute the
NSRect of the marker in the view and then call -scrollRectToVisible: to scroll
that into view. Works great, and the scrolling is animated, which is what I
want.
Now I want the 3-finger “swipe” gesture do the same thing. So I implemented
-swipeWithEvent: to check the dx and dy of the event and then call exactly the
same code that the arrow-keys call. It scrolls correctly … but it doesn’t
animate. It just jumps.
Any idea what’s going on here? I suspect NSScrollView has a bunch of
complicated heuristics about when it will animate and when not, and I’m running
afoul of those somehow. But I don’t see why — I’m basically just doing:
- (void)swipeWithEvent:(NSEvent *)event {
if (event.deltaY == 0) {
[self moveSelectionBy: event.deltaX];
[self scrollRectToVisible: [self rectForSelection]];
}
}
—Jens
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