frontend-admin / Daocheng-Yading

const ds = (ab) => (ab[0] <= 0 && ab[1] >= 0) || (ab[0] >= 0 && ab[1] <= 0);
const sign = (x) => (x < 0 ? -1 : 1);
export const pinchOrZoom = (event, cache) => {
    if (!event.changedTouches) {
        return false;
    }
    if (event.touches.length === 2) {
        const oldPoints = [cache[event.touches[0].identifier], cache[event.touches[1].identifier]];
        const newPoints = [event.touches[0], event.touches[1]];
        if (oldPoints[0] && oldPoints[1]) {
            // Calculate the difference between the start and move coordinates
            const diffx = [oldPoints[0].clientX - newPoints[0].clientX, oldPoints[1].clientX - newPoints[1].clientX];
            const diffy = [oldPoints[0].clientY - newPoints[0].clientY, oldPoints[1].clientY - newPoints[1].clientY];
            console.log(diffx, diffy);
            if (ds(diffx) || ds(diffy)) {
                return {
                    action: 'zoom',
                };
            }
            const mx = Math.max(Math.abs(diffx[0]), Math.abs(diffx[1]));
            const my = Math.max(Math.abs(diffy[0]), Math.abs(diffy[1]));
            return {
                action: 'pinch',
                coords: [mx * sign(diffx[0]), my * sign(diffx[1])],
            };
        }
    }
    Array.from(event.changedTouches).forEach((touch) => (cache[touch.identifier] = touch));
    return {
        action: 'move',
        coords: [event.changedTouches[0].clientX, event.changedTouches[0].clientY],
    };
};