Input System

SnapEngine normalizes pointer, wheel, drag, and pinch input into one event model. DOM-backed objects use native pointer capture while SnapEngine retains gesture recognition, object routing, and engine-wide fan-out. Capture begins when a drag or pinch is recognized so pre-threshold controls retain native click targeting.

SnapEgnine objects can all listen to three types of events: pointer event, drag event, and gesture event.

Pointer Event

Pointer Events are the simplest type of events. Currently the engine defines these:

• pointerDown
• pointerMove
• pointerUp
• mouseWheel

These events pass the position of the event in the engine’s world coordinates. For touch devices, the mouseWheel event is never fires, and other pointer events are fired for every touch input (multi touch support). pointerMove will continuously fire for each touch input.

Drag Event

Drag events are designed to handle continuous interaction that persists even when the pointer leaves the browser window or the original element.

The engine defines these drag events:

• dragStart
• drag
• dragEnd

These events provide the same world coordinate positions as pointer events but are specifically tailored for drag-and-drop interactions, panning, and other global gestures.

Gesture Event

Gesture events build on lower-level pointer events. They keep track of starts, deltas, endings, and multi-touch state so interaction logic can focus on behavior rather than browser event bookkeeping.

The engine defines these gesture events:

• pinchStart
• pinch
• pinchEnd

These events provide information about multi-touch gestures like pinches.

Global and Local Event

Targeted events begin at the DOM-owning ElementObject and bubble through its BaseObject parents, leaf to root. Engine-wide listeners run afterward. claimPointer() suppresses the global delivery for an active pointer without changing targeted delivery.

An active dragStart, drag, pinchStart, or pinch payload exposes handoffTo(objectOrId). Drag handoff transfers native capture and logical pointer ownership to a connected DOM-backed object. Pinch handoff transfers only pinch delivery; each finger retains the capture and pointer/drag owner from where it started. Pointer and terminal payloads do not expose handoff.

For event names, payload shapes, object-level handlers, global handlers, and gesture examples, see Input System reference.