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"use strict";
const direction = {
NONE: null,
LEFT: "left",
RIGHT: "right",
DOWN: "down",
UP: "up",
};
function getSwipeThresholdInPx() {
// how big is the movement in pixels to be registered as swipe
return Math.min(screen.width, screen.height) * 0.15;
}
function handleTouchStart(handler, evt) {
const touchEvent = evt.touches[0];
if (window.visualViewport.scale === 1) {
handler._xStart = touchEvent.clientX;
handler._yStart = touchEvent.clientY;
handler._startScrollY = window.scrollY;
}
}
function handleTouchMove(handler, evt) {
if (!handler._xStart || !handler._yStart) {
return;
}
if (window.visualViewport.scale > 1) {
handler._xStart = null;
handler._yStart = null;
return;
}
const xDirection = handler._xStart - evt.touches[0].clientX;
const yDirection = handler._yStart - evt.touches[0].clientY;
let threshold = getSwipeThresholdInPx();
if (Math.abs(xDirection) > Math.abs(yDirection)) {
if (Math.abs(xDirection) < threshold) {
return;
} else if (xDirection > 0) {
handler._direction = direction.LEFT;
} else {
handler._direction = direction.RIGHT;
}
} else {
if (Math.abs(yDirection) < threshold) {
return;
} else if (yDirection > 0) {
handler._direction = direction.UP;
} else {
handler._direction = direction.DOWN;
}
}
}
function handleTouchEnd(handler, evt) {
evt.startScrollY = handler._startScrollY;
switch (handler._direction) {
case direction.NONE:
return;
case direction.LEFT:
handler._swipeLeftTask(evt);
break;
case direction.RIGHT:
handler._swipeRightTask(evt);
break;
case direction.DOWN:
handler._swipeDownTask(evt);
break;
case direction.UP:
handler._swipeUpTask(evt);
// no default
}
handler._xStart = null;
handler._yStart = null;
}
class Touch {
constructor(
target,
swipeLeft = () => {},
swipeRight = () => {},
swipeUp = () => {},
swipeDown = () => {}
) {
this._target = target;
this._swipeLeftTask = swipeLeft;
this._swipeRightTask = swipeRight;
this._swipeUpTask = swipeUp;
this._swipeDownTask = swipeDown;
this._xStart = null;
this._yStart = null;
this._direction = direction.NONE;
this._target.addEventListener("touchstart", (evt) => {
handleTouchStart(this, evt);
});
this._target.addEventListener("touchmove", (evt) => {
handleTouchMove(this, evt);
});
this._target.addEventListener("touchend", (evt) => {
handleTouchEnd(this, evt);
});
}
}
module.exports = Touch;
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