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import type { NumberLineState } from './types'
import { screenXToNumber } from './numberLineTicks'
interface UseNumberLineTouchOptions {
stateRef: React.MutableRefObject<NumberLineState>
canvasRef: React.RefObject<HTMLCanvasElement | null>
onStateChange: () => void
/** Called with instantaneous zoom velocity and focal point (0-1 fraction of canvas width). */
onZoomVelocity?: (velocity: number, focalX: number) => void
/** Called when a tap (short press, no movement) is detected. Coordinates are CSS px relative to canvas. */
onTap?: (screenX: number, screenY: number) => void
/** Called on mousemove (when not dragging) with CSS px coordinates. (-1, -1) signals mouse left. */
onHover?: (screenX: number, screenY: number) => void
/** Called when a long-press (≥500ms hold, <10px movement) is detected. Coordinates are CSS px relative to canvas. */
onLongPress?: (screenX: number, screenY: number) => void
}
const TAP_MAX_DURATION_MS = 300
const TAP_MAX_DISTANCE_PX = 10
const LONG_PRESS_MS = 500
// Zoom limits — 1e14 allows viewing down to ~femto-scale (power -15)
// while staying well within float64's ~15 significant digits
const MIN_PIXELS_PER_UNIT = 0.001
const MAX_PIXELS_PER_UNIT = 1e14
function clampPixelsPerUnit(ppu: number): number {
return Math.max(MIN_PIXELS_PER_UNIT, Math.min(MAX_PIXELS_PER_UNIT, ppu))
}
/**
* Hook that attaches touch, mouse, and wheel handlers to a canvas element
* for panning and zooming a number line.
*
* All math uses absolute anchor-based computations (not deltas) to prevent drift.
*/
export function useNumberLineTouch({
stateRef,
canvasRef,
onStateChange,
onZoomVelocity,
onTap,
onHover,
onLongPress,
}: UseNumberLineTouchOptions) {
// Anchor state for single-finger drag / mouse drag
const dragAnchorRef = useRef<number | null>(null)
// Anchor state for two-finger pinch
const pinchAnchorsRef = useRef<{ n1: number; n2: number; id1: number; id2: number } | null>(null)
// Tap detection state
const tapStartRef = useRef<{ time: number; x: number; y: number; cancelled: boolean } | null>(
null
)
// Long-press timer
const longPressTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
const getCanvasWidth = useCallback(() => {
return canvasRef.current?.getBoundingClientRect().width ?? 0
}, [canvasRef])
const getCanvasRect = useCallback(() => {
return canvasRef.current?.getBoundingClientRect()
}, [canvasRef])
useEffect(() => {
const canvas = canvasRef.current
if (!canvas) return
// --- Touch handlers ---
function handleTouchStart(e: TouchEvent) {
e.preventDefault()
const rect = getCanvasRect()
if (!rect) return
const canvasWidth = rect.width
const state = stateRef.current
if (e.touches.length === 1) {
// Single finger: anchor the number under the touch
const x = e.touches[0].clientX - rect.left
const y = e.touches[0].clientY - rect.top
const anchorNumber = screenXToNumber(x, state.center, state.pixelsPerUnit, canvasWidth)
dragAnchorRef.current = anchorNumber
pinchAnchorsRef.current = null
// Start tap detection
tapStartRef.current = { time: performance.now(), x, y, cancelled: false }
// Start long-press timer
if (longPressTimerRef.current) clearTimeout(longPressTimerRef.current)
longPressTimerRef.current = setTimeout(() => {
const tap = tapStartRef.current
if (tap && !tap.cancelled) {
tap.cancelled = true // prevent tap from also firing
onLongPress?.(tap.x, tap.y)
}
longPressTimerRef.current = null
}, LONG_PRESS_MS)
} else if (e.touches.length === 2) {
// Two fingers: anchor both numbers
const x1 = e.touches[0].clientX - rect.left
const x2 = e.touches[1].clientX - rect.left
const n1 = screenXToNumber(x1, state.center, state.pixelsPerUnit, canvasWidth)
const n2 = screenXToNumber(x2, state.center, state.pixelsPerUnit, canvasWidth)
pinchAnchorsRef.current = {
n1,
n2,
id1: e.touches[0].identifier,
id2: e.touches[1].identifier,
}
dragAnchorRef.current = null
// Cancel tap and long-press on second finger
if (tapStartRef.current) tapStartRef.current.cancelled = true
if (longPressTimerRef.current) {
clearTimeout(longPressTimerRef.current)
longPressTimerRef.current = null
}
}
}
function handleTouchMove(e: TouchEvent) {
e.preventDefault()
const rect = getCanvasRect()
if (!rect) return
const canvasWidth = rect.width
const state = stateRef.current
// Cancel tap and long-press if finger moved too far
if (tapStartRef.current && !tapStartRef.current.cancelled && e.touches.length === 1) {
const tx = e.touches[0].clientX - rect.left
const ty = e.touches[0].clientY - rect.top
const dx = tx - tapStartRef.current.x
const dy = ty - tapStartRef.current.y
if (Math.sqrt(dx * dx + dy * dy) > TAP_MAX_DISTANCE_PX) {
tapStartRef.current.cancelled = true
if (longPressTimerRef.current) {
clearTimeout(longPressTimerRef.current)
longPressTimerRef.current = null
}
}
}
if (e.touches.length === 2 && pinchAnchorsRef.current) {
// Two-finger pinch + drag
const { n1, n2, id1, id2 } = pinchAnchorsRef.current
// Find touches by identifier
let touch1: Touch | null = null
let touch2: Touch | null = null
for (let i = 0; i < e.touches.length; i++) {
if (e.touches[i].identifier === id1) touch1 = e.touches[i]
if (e.touches[i].identifier === id2) touch2 = e.touches[i]
}
if (!touch1 || !touch2) return
const screen1 = touch1.clientX - rect.left
const screen2 = touch2.clientX - rect.left
const oldPPU = state.pixelsPerUnit
// Edge case: anchors too close together
if (Math.abs(n1 - n2) < 1e-12) {
// Treat as single-finger drag using midpoint
const midScreen = (screen1 + screen2) / 2
const midAnchor = (n1 + n2) / 2
state.center = midAnchor - (midScreen - canvasWidth / 2) / state.pixelsPerUnit
} else {
// Solve two equations for pixelsPerUnit and center
const newPPU = clampPixelsPerUnit((screen1 - screen2) / (n1 - n2))
state.pixelsPerUnit = newPPU
state.center = n1 - (screen1 - canvasWidth / 2) / newPPU
}
stateRef.current = state
onStateChange()
// Report zoom velocity for pinch (focal point = midpoint of two fingers)
if (state.pixelsPerUnit !== oldPPU) {
const midX = (screen1 + screen2) / 2
onZoomVelocity?.(Math.log(state.pixelsPerUnit / oldPPU), midX / canvasWidth)
}
} else if (e.touches.length === 1 && dragAnchorRef.current !== null) {
// Single finger drag
const x = e.touches[0].clientX - rect.left
const anchor = dragAnchorRef.current
state.center = anchor - (x - canvasWidth / 2) / state.pixelsPerUnit
stateRef.current = state
onStateChange()
}
}
function handleTouchEnd(e: TouchEvent) {
e.preventDefault()
const rect = getCanvasRect()
if (!rect) return
const canvasWidth = rect.width
const state = stateRef.current
if (e.touches.length === 1 && pinchAnchorsRef.current) {
// Transition 2 -> 1 finger: re-anchor remaining finger
const remainingTouch = e.touches[0]
const x = remainingTouch.clientX - rect.left
const anchorNumber = screenXToNumber(x, state.center, state.pixelsPerUnit, canvasWidth)
dragAnchorRef.current = anchorNumber
pinchAnchorsRef.current = null
} else if (e.touches.length === 0) {
// Clear long-press timer
if (longPressTimerRef.current) {
clearTimeout(longPressTimerRef.current)
longPressTimerRef.current = null
}
// Fire tap if conditions met
const tap = tapStartRef.current
if (tap && !tap.cancelled) {
const elapsed = performance.now() - tap.time
if (elapsed < TAP_MAX_DURATION_MS) {
onTap?.(tap.x, tap.y)
}
}
tapStartRef.current = null
dragAnchorRef.current = null
pinchAnchorsRef.current = null
}
}
// --- Mouse handlers ---
let mouseAnchor: number | null = null
let mouseDownInfo: { time: number; x: number; y: number; cancelled: boolean } | null = null
let mouseLongPressTimer: ReturnType<typeof setTimeout> | null = null
function handleMouseDown(e: MouseEvent) {
if (e.button !== 0) return // left button only
const rect = getCanvasRect()
if (!rect) return
const canvasWidth = rect.width
const x = e.clientX - rect.left
const y = e.clientY - rect.top
const state = stateRef.current
mouseAnchor = screenXToNumber(x, state.center, state.pixelsPerUnit, canvasWidth)
mouseDownInfo = { time: performance.now(), x, y, cancelled: false }
canvas!.style.cursor = 'grabbing'
// Start long-press timer for mouse
if (mouseLongPressTimer) clearTimeout(mouseLongPressTimer)
mouseLongPressTimer = setTimeout(() => {
if (mouseDownInfo && !mouseDownInfo.cancelled) {
mouseDownInfo.cancelled = true
onLongPress?.(mouseDownInfo.x, mouseDownInfo.y)
}
mouseLongPressTimer = null
}, LONG_PRESS_MS)
}
function handleMouseMove(e: MouseEvent) {
if (mouseAnchor === null) return
const rect = getCanvasRect()
if (!rect) return
const canvasWidth = rect.width
const x = e.clientX - rect.left
const y = e.clientY - rect.top
const state = stateRef.current
state.center = mouseAnchor - (x - canvasWidth / 2) / state.pixelsPerUnit
stateRef.current = state
onStateChange()
// Cancel mouse tap and long-press if moved too far
if (mouseDownInfo && !mouseDownInfo.cancelled) {
const dx = x - mouseDownInfo.x
const dy = y - mouseDownInfo.y
if (Math.sqrt(dx * dx + dy * dy) > TAP_MAX_DISTANCE_PX) {
mouseDownInfo.cancelled = true
if (mouseLongPressTimer) {
clearTimeout(mouseLongPressTimer)
mouseLongPressTimer = null
}
}
}
}
function handleMouseUp(e: MouseEvent) {
// Clear long-press timer
if (mouseLongPressTimer) {
clearTimeout(mouseLongPressTimer)
mouseLongPressTimer = null
}
// Fire tap if conditions met
if (mouseDownInfo && !mouseDownInfo.cancelled) {
const elapsed = performance.now() - mouseDownInfo.time
if (elapsed < TAP_MAX_DURATION_MS) {
const rect = getCanvasRect()
if (rect) {
const x = e.clientX - rect.left
const y = e.clientY - rect.top
onTap?.(x, y)
}
}
}
mouseDownInfo = null
mouseAnchor = null
if (canvas) canvas.style.cursor = 'grab'
}
// --- Wheel handler ---
function handleWheel(e: WheelEvent) {
e.preventDefault()
const rect = getCanvasRect()
if (!rect) return
const canvasWidth = rect.width
const x = e.clientX - rect.left
const state = stateRef.current
// Anchor the number under the cursor
const anchorNumber = screenXToNumber(x, state.center, state.pixelsPerUnit, canvasWidth)
// Zoom factor: positive deltaY = scroll down = zoom out
const oldPPU = state.pixelsPerUnit
const zoomFactor = 1.001 ** -e.deltaY
const newPPU = clampPixelsPerUnit(oldPPU * zoomFactor)
state.pixelsPerUnit = newPPU
// Re-center so anchorNumber stays under the cursor
state.center = anchorNumber - (x - canvasWidth / 2) / newPPU
stateRef.current = state
onStateChange()
// Report zoom velocity and focal point
onZoomVelocity?.(Math.log(newPPU / oldPPU), x / canvasWidth)
}
// --- Hover handler (independent of drag) ---
function handleCanvasMouseMove(e: MouseEvent) {
// Only fire hover when not dragging
if (mouseAnchor !== null) return
const rect = getCanvasRect()
if (!rect) return
const x = e.clientX - rect.left
const y = e.clientY - rect.top
onHover?.(x, y)
}
function handleCanvasMouseLeave() {
onHover?.(-1, -1)
}
// Attach listeners
canvas.addEventListener('touchstart', handleTouchStart, { passive: false })
canvas.addEventListener('touchmove', handleTouchMove, { passive: false })
canvas.addEventListener('touchend', handleTouchEnd, { passive: false })
canvas.addEventListener('touchcancel', handleTouchEnd, { passive: false })
canvas.addEventListener('mousedown', handleMouseDown)
window.addEventListener('mousemove', handleMouseMove)
window.addEventListener('mouseup', handleMouseUp)
canvas.addEventListener('wheel', handleWheel, { passive: false })
canvas.addEventListener('mousemove', handleCanvasMouseMove)
canvas.addEventListener('mouseleave', handleCanvasMouseLeave)
// Set initial cursor
canvas.style.cursor = 'grab'
return () => {
canvas.removeEventListener('touchstart', handleTouchStart)
canvas.removeEventListener('touchmove', handleTouchMove)
canvas.removeEventListener('touchend', handleTouchEnd)
canvas.removeEventListener('touchcancel', handleTouchEnd)
canvas.removeEventListener('mousedown', handleMouseDown)
window.removeEventListener('mousemove', handleMouseMove)
window.removeEventListener('mouseup', handleMouseUp)
canvas.removeEventListener('wheel', handleWheel)
canvas.removeEventListener('mousemove', handleCanvasMouseMove)
canvas.removeEventListener('mouseleave', handleCanvasMouseLeave)
if (longPressTimerRef.current) clearTimeout(longPressTimerRef.current)
if (mouseLongPressTimer) clearTimeout(mouseLongPressTimer)
}
}, [
canvasRef,
stateRef,
onStateChange,
onZoomVelocity,
onTap,
onHover,
onLongPress,
getCanvasWidth,
getCanvasRect,
])
}
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