The default behavior of PointerMoveEvent for touch input in the UI Toolkit is to only fire while the touch remains within the original bounds of your visual element. This differs significantly from mouse input, which often maintains an active state more loosely. This limitation prevents smooth dragging on mobile devices because a fast or wide gesture often exceeds the initial hit-box of the element.

To enable reliable dragging, you must utilize the pointer capture system. This programmatically locks the pointerId to your visual element, ensuring that all subsequent movement and release events are routed to it regardless of the current touch position.

1. Within the PointerDownEvent callback, invoke CapturePointer on your visual element using the pointerId from the event arguments.
2. During the PointerMoveEvent, verify the element still has focus by checking HasPointerCapture with the pointerId before applying translation logic.
3. Within the PointerUpEvent callback, invoke ReleasePointer to free the pointerId and allow other elements to receive input.

Additional Tips

• Listen for PointerCaptureOutEvent to handle cases where the system cancels the touch (e.g., an incoming phone call or OS gesture).
• Ensure your visual element has a usageHints set to UsageHints.DynamicTransform if it moves frequently to optimize performance.
• Verify that the pickingMode property of your visual element is set to PickingMode.Position so it can intercept pointer events.