panZoom
Adds captured pointer panning and pointer-anchored scroll zooming.
A matching press is consumed and acquires the tree's generic pointer capture, so matching drags and release continue outside this modifier's bounds and ancestor clips. Dragging moves content with the pointer by adjusting the content center against the resolved scale. Vertical scrolling applies zoomStep ^ -deltaY around the event's modifier-local position and consumes the scroll event. Other buttons, pointer moves, and horizontal-only scrolling remain available to ordinary dispatch. Capture cancellation forgets the unfinished gesture without changing the last committed transform. The caller owns state, and all interaction must run on its owner thread.
Return
this chain with one appended active pan-and-zoom input node.
Parameters
caller-owned transform updated synchronously by input.
button that begins a captured pan gesture.
finite factor greater than one for each logical vertical scroll unit.
Throws
when zoomStep is not finite or is not greater than one, or accepted input cannot produce a finite transform.
when input runs on a thread other than the state owner.
when accepted input publishes state and an observer callback fails.