Function attachPointer

attachPointer(
    target: EventTarget & {
        getBoundingClientRect?: () => { left: number; top: number };
    },
    options?: PointerOptions,
): PointerTracker
Pointer input as signals - down, move, drag, up - with positions relative to target and, through toWorld, in world units, so a game does not reach for the renderer's own event system to build a draggable thing. One pointer is tracked at a time (the first to press), which is what a mouse or a single finger is; a second finger is ignored until the first lifts.
Parameters
- target: EventTarget & { getBoundingClientRect?: () => { left: number; top: number } }
- options: PointerOptions = {}
Returns PointerTracker
Example
```
import { Input } from '@datamoc/mwg/core';

const target = new EventTarget(); // the game's canvas in a browser
const pointer = Input.attachPointer(target, { dragThreshold: 6 });
pointer.drag.add((p) => console.log('dragging', p.worldX, p.worldY));
pointer.up.add((p) => console.log(p.dragged ? 'dropped' : 'clicked'));
pointer.detach();
```
- Defined in src/core/Input.ts:615