I have a fairly robust MacOS application that has an NSScrollView that contains a canvas with various subviews (including web views and text views that contain scroll views), and a couple of peer views that track items in the scroll view (eg: screen space controls).
Some of these views interrupt two finger scrolling. Every scroll view, and one of the peer views (essentially a stack view with buttons in it).
I have written an additional bare bones application which does roughly the same thing, and my bare bones application works perfectly: Start two-finger dragging, scroll any of these other things under the cursor, I can continue to drag (and start dragging in any of those, and they drag without interfering with the parent scroll view).
I have tried everything to recreate the interruption, including drag gestures attached to these various ancillary views, and I cannot figure out why dragging some of these views under the cursor interrupts two finger drag in our application, but not in my testbed.
Does anyone have suggestions for how to debug this? I can see that there is a gesture recognizer in the NSScrollView hierarchy, but I don't see it in any of my gesture recognizer handling. I have breakpoints on every variation of hit testing and mouse motion, and none of them are getting hit in unexpected ways.
I'm at my wit's end. Thanks.