While testing in Unity Editor, Scroll Rect UI moves on mouse-drag as normal, but when testing on ML2 dragging scroll rect content does not work (dragging scroll bars do work however). We are just using the Unity Input System (1.5.0) (no XRI or MRTK package), and are using the "Input System UI Input Module" component and binding tracked position and rotation to ML2 hands using hand pinch as a "Left Click". All other UI interaction seems to be working. I found this link that shows a similar issue that's been fixed for Oculus Here; I wonder if it could be related, with both devices being Android-based.
Doesn't the XRI simulator simply augment the Unity input system by creating a virtual XR device bound to keyboard actions? Either way it works. I'll report the issue. My gut tells me it's some issue on-device similar to the exact Bug Oculus had that I mentioned above.
@sascha We have reported the issue to Unity. As a workaround, we found that setting the Tracked Device Drag Threshold to a really low number on the XR UI Input Module resolves this issue. Try setting the value to 0.005, this should allow the application to report the On Drag Events properly.
I will keep you updated if I get any information regarding an official fix.
@kbabilinski Unfortunately we're using the "Input System UI Input Module" and not "XR UI Input Module" to drive input for our UI... this means the only exposed field for drag threshold is in the "Event System" component, and that field is an integer value (pixel-based); there's no way to set it to a decimal. If I set it to "1" the scrolling issue persists. If I set it to "0", scrolling works but then button clicks don't work - Unity's logic will always think I'm dragging and forgo the "OnClick" event. I guess we must continue to wait on Unity.