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import { avg, iterateDOMList } from '$lib/utils.js';
export type ClientPoint = { clientX: number; clientY: number };
type PanEvent =
| {
kind: 'panend';
source: TouchEvent;
}
| {
kind: 'panstart';
source: TouchEvent;
origin: ClientPoint;
}
| {
kind: 'panmove';
source: TouchEvent;
/** Center of the {@link starts} points */
origin: ClientPoint;
/** Center of the {@link ends} points */
destination: ClientPoint;
dx: number;
dy: number;
};
export type PinchEvent = {
source: TouchEvent;
/** Center of the {@link starts} points */
origin: ClientPoint;
/** Euclidian distance of the movement of two points */
distance: number;
};
type DoubleTapEvent = {
fingercount: number;
source: TouchEvent;
};
export class Gestures {
#panning = false;
/**
* Key is the Touch's identifier
* Touches when the touch event started
*/
#startingTouches = new SvelteMap<number, Touch>();
/**
* Each tap is an array of touches
*/
#taps = [] as Touch[][];
#handle = (event: TouchEvent) => {
/** Length of the vector between the two points */
const distance = (...[p1, p2]: ClientPoint[]) =>
Math.hypot(p1.clientX - p2.clientX, p1.clientY - p2.clientY);
/** Ratio of distance to diagonal of screen */
const reldistance = (...[p1, p2]: ClientPoint[]) =>
distance(p1, p2) / Math.hypot(screen.width, screen.height);
/** Center of the given points */
const center = (points: ClientPoint[]) => ({
clientX: avg(points.map((p) => p.clientX)),
clientY: avg(points.map((p) => p.clientY)),
});
if (event.type === 'touchstart') {
this.#startingTouches = new SvelteMap(
[...iterateDOMList(event.touches)].map((touch) => [touch.identifier, touch])
);
}
Iif (event.type === 'touchend') {
// If we still have some fingers touching, this isnt really a end of touch, bail
if (event.touches.length > 0) {
return;
}
if (this.#panning) {
this.handlers?.onpan?.({
kind: 'panend',
source: event,
});
} else {
// No panning = no touchmove = its a tap
this.#taps.push([...this.#startingTouches.values()]);
// Handle double taps
if (this.#taps.length >= 2) {
const [first, second] = this.#taps;
if (reldistance(center(first), center(second)) < 0.1) {
this.handlers?.ondoubletap?.({
fingercount: Math.min(...this.#taps.map((tap) => tap.length)),
source: event,
});
}
this.#taps = [];
}
}
this.#startingTouches.clear();
}
if (event.type === 'touchmove' && event.touches.length === 2) {
const start = [...this.#startingTouches.values()];
const end = [...iterateDOMList(event.touches)];
// Ratio of distances between centers (the center moved, so more pan-like)
// and the distances of starts and ends (the pinch distance)
const eccentricity =
distance(center(start), center(end)) /
Math.abs(distance(...end) - distance(...start));
// Might be 1 in theory, idk, but 2 seems good empirically
if (eccentricity > 1) {
Eif (!this.#panning) {
this.handlers.onpan?.({
kind: 'panstart',
source: event,
origin: center(start),
});
}
this.#panning = true;
this.handlers.onpan?.({
kind: 'panmove',
source: event,
origin: center(start),
destination: center(end),
dx: center(end).clientX - center(start).clientX,
dy: center(end).clientY - center(start).clientY,
});
} else {
this.#panning = false;
this.handlers.onpan?.({
kind: 'panend',
source: event,
});
// TODO: batch sends on the handler to improve performance
// it's sent too often in small increments, it can make zooming
// laggy... but it's not that bad tbh
this.handlers.onpinch?.({
source: event,
origin: center(start),
distance: distance(...end) - distance(...start),
});
}
}
};
constructor(
public inside: HTMLElement,
public handlers: {
onpinch?: (event: PinchEvent) => void;
onpan?: (event: PanEvent) => void;
ondoubletap?: (event: DoubleTapEvent) => void;
}
) {
// https://developer.mozilla.org/en-US/docs/Web/API/Pointer_events/Pinch_zoom_gestures
$effect(() => {
const handler = this.#handle;
this.inside.addEventListener('touchstart', handler);
this.inside.addEventListener('touchend', handler);
this.inside.addEventListener('touchmove', handler);
// prevent default for two-finger-tap if we have a ondoubletap handler set
const preventDefault = (e: Event) => e.preventDefault();
Iif (this.handlers.ondoubletap) {
this.inside.addEventListener('contextmenu', preventDefault);
}
return () => {
this.inside.removeEventListener('touchstart', handler);
this.inside.removeEventListener('touchend', handler);
this.inside.removeEventListener('touchmove', handler);
this.inside.removeEventListener('contextmenu', preventDefault);
};
});
}
}
|