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feat(core): improve touch zoom gestures #10303

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249 changes: 210 additions & 39 deletions modules/core/src/controllers/controller.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -20,13 +20,20 @@ const NO_TRANSITION_PROPS = {

const DEFAULT_INERTIA = 300;
const INERTIA_EASING = t => 1 - (1 - t) * (1 - t);
const MAX_PINCH_ZOOM_DELTA_PER_EVENT = 0.18;
const DOUBLE_TAP_DRAG_INTERVAL = 500;
const DOUBLE_TAP_DRAG_MAX_TAP_DURATION = 350;
const DOUBLE_TAP_DRAG_MAX_TAP_DISTANCE = 28;
const DOUBLE_TAP_DRAG_START_THRESHOLD = 1;
const DOUBLE_TAP_DRAG_PIXELS_PER_ZOOM = 120;

const EVENT_TYPES = {
WHEEL: ['wheel'],
PAN: ['panstart', 'panmove', 'panend'],
PINCH: ['pinchstart', 'pinchmove', 'pinchend'],
MULTI_PAN: ['multipanstart', 'multipanmove', 'multipanend'],
DOUBLE_CLICK: ['dblclick'],
DOUBLE_TAP_DRAG: ['pointerdown', 'pointermove', 'pointerup', 'pointercancel'],
KEYBOARD: ['keydown']
} as const;

Expand Down Expand Up @@ -112,6 +119,28 @@ export type ViewStateChangeParameters<ViewStateT = any> = {

const pinchEventWorkaround: any = {};

type OneFingerTapState = {
pos: [number, number];
time: number;
pointerId?: number;
};

type OneFingerZoomState = {
startPos: [number, number];
pointerId?: number;
active: boolean;
};

function getDistance(a: [number, number], b: [number, number]): number {
const dx = a[0] - b[0];
const dy = a[1] - b[1];
return Math.sqrt(dx * dx + dy * dy);
}

function clampPinchZoomDelta(delta: number): number {
return Math.max(-MAX_PINCH_ZOOM_DELTA_PER_EVENT, Math.min(MAX_PINCH_ZOOM_DELTA_PER_EVENT, delta));
}

export default abstract class Controller<ControllerState extends IViewState<ControllerState>> {
abstract get ControllerState(): ConstructorOf<ControllerState>;
abstract get transition(): TransitionProps;
Expand All @@ -135,6 +164,10 @@ export default abstract class Controller<ControllerState extends IViewState<Cont
private _customEvents: string[] = [];
private _eventStartBlocked: any = null;
private _panMove: boolean = false;
private _tapStart: OneFingerTapState | null = null;
private _lastTap: OneFingerTapState | null = null;
private _oneFingerZoom: OneFingerZoomState | null = null;
private _suppressDoubleClickUntil: number = 0;

protected invertPan: boolean = false;
protected dragMode: 'pan' | 'rotate' = 'rotate';
Expand Down Expand Up @@ -209,10 +242,19 @@ export default abstract class Controller<ControllerState extends IViewState<Cont

switch (event.type) {
case 'panstart':
if (this._oneFingerZoom) {
return false;
}
return eventStartBlocked ? false : this._onPanStart(event);
case 'panmove':
if (this._oneFingerZoom) {
return false;
}
return this._onPan(event);
case 'panend':
if (this._oneFingerZoom) {
return false;
}
return this._onPanEnd(event);
case 'pinchstart':
return eventStartBlocked ? false : this._onPinchStart(event);
Expand All @@ -228,6 +270,13 @@ export default abstract class Controller<ControllerState extends IViewState<Cont
return this._onMultiPanEnd(event);
case 'dblclick':
return this._onDoubleClick(event);
case 'pointerdown':
return this._onPointerDown(event);
case 'pointermove':
return this._onPointerMove(event);
case 'pointerup':
case 'pointercancel':
return this._onPointerUp(event);
case 'wheel':
return this._onWheel(event as MjolnirWheelEvent);
case 'keydown':
Expand Down Expand Up @@ -328,6 +377,7 @@ export default abstract class Controller<ControllerState extends IViewState<Cont
this.toggleEvents(EVENT_TYPES.PINCH, isInteractive && (touchZoom || touchRotate));
this.toggleEvents(EVENT_TYPES.MULTI_PAN, isInteractive && touchRotate);
this.toggleEvents(EVENT_TYPES.DOUBLE_CLICK, isInteractive && doubleClickZoom);
this.toggleEvents(EVENT_TYPES.DOUBLE_TAP_DRAG, isInteractive && touchZoom);
this.toggleEvents(EVENT_TYPES.KEYBOARD, isInteractive && keyboard);

// Interaction toggles
Expand Down Expand Up @@ -641,6 +691,7 @@ export default abstract class Controller<ControllerState extends IViewState<Cont

// Default handler for the `pinchstart` event.
protected _onPinchStart(event: MjolnirGestureEvent): boolean {
this._resetOneFingerZoom();
const pos = this.getCenter(event);
if (!this.isPointInBounds(pos, event)) {
return false;
Expand All @@ -649,7 +700,7 @@ export default abstract class Controller<ControllerState extends IViewState<Cont
const newControllerState = this.controllerState.zoomStart({pos}).rotateStart({pos});
// hack - hammer's `rotation` field doesn't seem to produce the correct angle
pinchEventWorkaround._startPinchRotation = event.rotation;
pinchEventWorkaround._lastPinchEvent = event;
pinchEventWorkaround._smoothedPinchScaleLog = 0;
this.updateViewport(newControllerState, NO_TRANSITION_PROPS, {isDragging: true});
return true;
}
Expand All @@ -667,7 +718,12 @@ export default abstract class Controller<ControllerState extends IViewState<Cont
if (this.touchZoom) {
const {scale} = event;
const pos = this.getCenter(event);
newControllerState = newControllerState.zoom({pos, scale});
const rawScaleLog = Math.log2(scale);
const previousScaleLog = pinchEventWorkaround._smoothedPinchScaleLog ?? 0;
const smoothedScaleLog =
previousScaleLog + clampPinchZoomDelta(rawScaleLog - previousScaleLog);
pinchEventWorkaround._smoothedPinchScaleLog = smoothedScaleLog;
newControllerState = newControllerState.zoom({pos, scale: Math.pow(2, smoothedScaleLog)});
}
if (this.touchRotate) {
const {rotation} = event;
Expand All @@ -682,51 +738,22 @@ export default abstract class Controller<ControllerState extends IViewState<Cont
isZooming: this.touchZoom,
isRotating: this.touchRotate
});
pinchEventWorkaround._lastPinchEvent = event;
return true;
}

protected _onPinchEnd(event: MjolnirGestureEvent): boolean {
if (!this.isDragging()) {
return false;
}
const {inertia} = this;
const {_lastPinchEvent} = pinchEventWorkaround;
if (this.touchZoom && inertia && _lastPinchEvent && event.scale !== _lastPinchEvent.scale) {
const pos = this.getCenter(event);
let newControllerState = this.controllerState.rotateEnd();
const z = Math.log2(event.scale);
const velocityZ =
(z - Math.log2(_lastPinchEvent.scale)) / (event.deltaTime - _lastPinchEvent.deltaTime);
const endScale = Math.pow(2, z + (velocityZ * inertia) / 2);
newControllerState = newControllerState.zoom({pos, scale: endScale}).zoomEnd();

this.updateViewport(
newControllerState,
{
...this._getTransitionProps({around: pos}),
transitionDuration: inertia,
transitionEasing: INERTIA_EASING
},
{
isDragging: false,
isPanning: this.touchZoom,
isZooming: this.touchZoom,
isRotating: false
}
);
this.blockEvents(inertia);
} else {
const newControllerState = this.controllerState.zoomEnd().rotateEnd();
this.updateViewport(newControllerState, null, {
isDragging: false,
isPanning: false,
isZooming: false,
isRotating: false
});
}
const newControllerState = this.controllerState.zoomEnd().rotateEnd();
this.updateViewport(newControllerState, null, {
isDragging: false,
isPanning: false,
isZooming: false,
isRotating: false
});
pinchEventWorkaround._startPinchRotation = null;
pinchEventWorkaround._lastPinchEvent = null;
pinchEventWorkaround._smoothedPinchScaleLog = null;
return true;
}

Expand All @@ -735,6 +762,9 @@ export default abstract class Controller<ControllerState extends IViewState<Cont
if (!this.doubleClickZoom) {
return false;
}
if (Date.now() < this._suppressDoubleClickUntil) {
return false;
}
const pos = this.getCenter(event);
if (!this.isPointInBounds(pos, event)) {
return false;
Expand All @@ -751,6 +781,147 @@ export default abstract class Controller<ControllerState extends IViewState<Cont
return true;
}

protected _onPointerDown(event: MjolnirEvent): boolean {

@felixpalmer felixpalmer May 15, 2026

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This code feels very low level and should go in mjolnir, WDYT @Pessimistress ?

if (!this.touchZoom || !this._isPrimaryPointer(event)) {
this._resetOneFingerZoom();
return false;
}

const pos = this.getCenter(event as MjolnirGestureEvent);
if (!this.isPointInBounds(pos, event)) {
this._resetOneFingerZoom();
return false;
}

const time = this._getEventTime(event);
const pointerId = (event.srcEvent as PointerEvent).pointerId;
if (
this._lastTap &&
time - this._lastTap.time <= DOUBLE_TAP_DRAG_INTERVAL &&
getDistance(pos, this._lastTap.pos) <= DOUBLE_TAP_DRAG_MAX_TAP_DISTANCE
) {
this._tapStart = null;
this._lastTap = null;
this._oneFingerZoom = {startPos: pos, pointerId, active: false};
event.srcEvent.preventDefault();
event.stopPropagation();
return true;
}

this._tapStart = {pos, time, pointerId};
this._lastTap = null;
if ((event.srcEvent as PointerEvent).pointerType === 'touch') {
event.srcEvent.preventDefault();
}
return false;
}

protected _onPointerMove(event: MjolnirEvent): boolean {
const oneFingerZoom = this._oneFingerZoom;
if (!oneFingerZoom || !this._isSamePointer(event, oneFingerZoom.pointerId)) {
return false;
}

const pos = this.getCenter(event as MjolnirGestureEvent);
const dy = oneFingerZoom.startPos[1] - pos[1];
if (!oneFingerZoom.active && Math.abs(dy) < DOUBLE_TAP_DRAG_START_THRESHOLD) {
event.srcEvent.preventDefault();
event.stopPropagation();
return true;
}

const scale = Math.pow(2, dy / DOUBLE_TAP_DRAG_PIXELS_PER_ZOOM);
const startPos = oneFingerZoom.startPos;
let newControllerState = this.controllerState;
if (!oneFingerZoom.active) {
oneFingerZoom.active = true;
newControllerState = newControllerState.zoomStart({pos: startPos});
}
newControllerState = newControllerState.zoom({pos: startPos, scale});
this.updateViewport(newControllerState, NO_TRANSITION_PROPS, {
isDragging: true,
isPanning: true,
isZooming: true
});

event.srcEvent.preventDefault();
event.stopPropagation();
return true;
}

protected _onPointerUp(event: MjolnirEvent): boolean {
const oneFingerZoom = this._oneFingerZoom;
if (oneFingerZoom && this._isSamePointer(event, oneFingerZoom.pointerId)) {
this._oneFingerZoom = null;
if (oneFingerZoom.active) {
const newControllerState = this.controllerState.zoomEnd();
this.updateViewport(newControllerState, null, {
isDragging: false,
isPanning: false,
isZooming: false
});
this._suppressDoubleClickUntil = Date.now() + 100;
this.blockEvents(100);
event.srcEvent.preventDefault();
event.stopPropagation();
return true;
}
return false;
}

if (event.type === 'pointercancel') {
this._resetOneFingerZoom();
return false;
}

const tapStart = this._tapStart;
if (!tapStart || !this._isSamePointer(event, tapStart.pointerId)) {
return false;
}

const pos = this.getCenter(event as MjolnirGestureEvent);
const time = this._getEventTime(event);
if (
time - tapStart.time <= DOUBLE_TAP_DRAG_MAX_TAP_DURATION &&
getDistance(pos, tapStart.pos) <= DOUBLE_TAP_DRAG_MAX_TAP_DISTANCE
) {
this._lastTap = {pos, time, pointerId: tapStart.pointerId};
} else {
this._lastTap = null;
}
this._tapStart = null;
if ((event.srcEvent as PointerEvent).pointerType === 'touch') {
event.srcEvent.preventDefault();
}
return false;
}

private _resetOneFingerZoom(): void {
this._tapStart = null;
this._lastTap = null;
this._oneFingerZoom = null;
}

private _getEventTime(event: MjolnirEvent): number {
return (event as any).timeStamp || event.srcEvent.timeStamp || Date.now();
}

private _isPrimaryPointer(event: MjolnirEvent): boolean {
const pointers = (event as any).pointers;
if (pointers && pointers.length > 1) {
return false;
}
const srcEvent = event.srcEvent as PointerEvent;
if (srcEvent.pointerType === 'mouse') {
return (event as any).leftButton !== false;
}
return true;
}

private _isSamePointer(event: MjolnirEvent, pointerId?: number): boolean {
return pointerId === undefined || (event.srcEvent as PointerEvent).pointerId === pointerId;
}

// Default handler for the `keydown` event
protected _onKeyDown(event: MjolnirKeyEvent): boolean {
if (!this.keyboard) {
Expand Down
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