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/**
* Provides means to hook into the scroll event. Registered callbacks are
* called with the current scroll top and scroll left position so both
* vertical and horizontal scroll events can be handled.
*
* Updates/calls to the callback are synchronized to screen refresh by using
* the animation frame method (which will fallback to a timer based solution).
*/
var handlers = {};
var animId = false;
var lastTop = null;
var lastLeft = null;
function scrollHandler() {
var scrollTop = $(document).scrollTop();
var scrollLeft = $(document).scrollLeft();
if (scrollTop !== lastTop || scrollLeft !== lastLeft) {
$.each(handlers, function(index, handler) {
handler(scrollTop, scrollLeft);
});
lastTop = scrollTop;
lastLeft = scrollLeft;
}
animId = false;
engageScrollTrigger();
}
function refresh() {
var hasHandlers = !$.isEmptyObject(handlers);
if (!hasHandlers && animId !== false) {
window.cancelAnimationFrame(animId);
animId = false;
} else if (hasHandlers && animId === false) {
animId = window.requestAnimationFrame(scrollHandler);
}
}
function engageScrollTrigger() {
$(window).off('scroll.studip-handler');
$(window).one('scroll.studip-handler', refresh);
}
const Scroll = {
addHandler(index, handler) {
handlers[index] = handler;
engageScrollTrigger();
},
removeHandler(index) {
delete handlers[index];
engageScrollTrigger();
}
};
export default Scroll;
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