Tldraw/hooks/useCanvasEvents.ts

import { MutableRefObject, useCallback } from 'react'
import state from 'state'
import {
  fastBrushSelect,
  fastDrawUpdate,
  fastTransform,
  fastTranslate,
} from 'state/hacks'
import inputs from 'state/inputs'
import { isMobile } from 'utils/utils'

export default function useCanvasEvents(
  rCanvas: MutableRefObject<SVGGElement>
) {
  const handlePointerDown = useCallback((e: React.PointerEvent) => {
    if (!inputs.canAccept(e.pointerId)) return

    rCanvas.current.setPointerCapture(e.pointerId)

    if (e.button === 0) {
      state.send('POINTED_CANVAS', inputs.pointerDown(e, 'canvas'))
    } else if (e.button === 2) {
      state.send('RIGHT_POINTED', inputs.pointerDown(e, 'canvas'))
    }
  }, [])

  const handleTouchStart = useCallback((e: React.TouchEvent) => {
    if (isMobile()) {
      if (e.touches.length === 2) {
        state.send('TOUCH_UNDO')
      } else state.send('TOUCHED_CANVAS')
    }
  }, [])

  const handlePointerMove = useCallback((e: React.PointerEvent) => {
    if (!inputs.canAccept(e.pointerId)) return

    const info = inputs.pointerMove(e)

    if (state.isIn('draw.editing')) {
      fastDrawUpdate(info)
      return
    }

    if (state.isIn('brushSelecting')) {
      fastBrushSelect(info.point)
      return
    }

    if (state.isIn('translatingSelection')) {
      fastTranslate(info)
      return
    }

    if (state.isIn('transformingSelection')) {
      fastTransform(info)
      return
    }

    state.send('MOVED_POINTER', info)
  }, [])

  const handlePointerUp = useCallback((e: React.PointerEvent) => {
    if (!inputs.canAccept(e.pointerId)) return
    rCanvas.current.releasePointerCapture(e.pointerId)
    state.send('STOPPED_POINTING', { id: 'canvas', ...inputs.pointerUp(e) })
  }, [])

  return {
    onPointerDown: handlePointerDown,
    onTouchStart: handleTouchStart,
    onPointerMove: handlePointerMove,
    onPointerUp: handlePointerUp,
  }
}