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import * as doms from 'shared/utils/dom';
const SCROLL_DELTA_X = 48;
const SCROLL_DELTA_Y = 48;
const SMOOTH_SCROLL_DURATION = 150;
// dirty way to store scrolling state on globally
let scrolling = [false];
const isScrollableStyle = (element) => {
let { overflowX, overflowY } = window.getComputedStyle(element);
return !(overflowX !== 'scroll' && overflowX !== 'auto' &&
overflowY !== 'scroll' && overflowY !== 'auto');
};
const isOverflowed = (element) => {
return element.scrollWidth > element.clientWidth ||
element.scrollHeight > element.clientHeight;
};
// Find a visiable and scrollable element by depth-first search. Currently
// this method is called by each scrolling, and the returned value of this
// method is not cached. That does not cause performance issue because in the
// most pages, the window is root element i,e, documentElement.
const findScrollable = (element) => {
if (isScrollableStyle(element) && isOverflowed(element)) {
return element;
}
let children = Array.from(element.children).filter(doms.isVisible);
for (let child of children) {
let scrollable = findScrollable(child);
if (scrollable) {
return scrollable;
}
}
return null;
};
const scrollTarget = () => {
if (isOverflowed(window.document.documentElement)) {
return window.document.documentElement;
}
if (isOverflowed(window.document.body)) {
return window.document.body;
}
let target = findScrollable(window.document.documentElement);
if (target) {
return target;
}
return window.document.documentElement;
};
class SmoothScroller {
constructor(element, repeat) {
this.element = element;
this.repeat = repeat;
this.scrolling = scrolling;
if (repeat) {
this.easing = SmoothScroller.linearEasing;
} else {
this.easing = SmoothScroller.inOutQuadEasing;
}
}
scroll(x, y) {
if (this.scrolling[0]) {
return;
}
scrolling[0] = true;
this.startX = this.element.scrollLeft;
this.startY = this.element.scrollTop;
this.targetX = x;
this.targetY = y;
this.distanceX = x - this.startX;
this.distanceY = y - this.startY;
this.timeStart = 0;
window.requestAnimationFrame(this.loop.bind(this));
}
loop(time) {
if (!this.timeStart) {
this.timeStart = time;
}
let elapsed = time - this.timeStart;
let v = this.easing(elapsed / SMOOTH_SCROLL_DURATION);
let nextX = this.startX + this.distanceX * v;
let nextY = this.startY + this.distanceY * v;
window.scrollTo(nextX, nextY);
if (elapsed < SMOOTH_SCROLL_DURATION) {
window.requestAnimationFrame(this.loop.bind(this));
} else {
scrolling[0] = false;
this.element.scrollTo(this.targetX, this.targetY);
}
}
static inOutQuadEasing(t) {
if (t < 1) {
return t * t;
}
return -(t - 1) * (t - 1) + 1;
}
static linearEasing(t) {
return t;
}
}
class RoughtScroller {
constructor(element) {
this.element = element;
}
scroll(x, y) {
this.element.scrollTo(x, y);
}
}
const scroller = (element, smooth, repeat) => {
if (smooth) {
return new SmoothScroller(element, repeat);
}
return new RoughtScroller(element);
};
const getScroll = () => {
let target = scrollTarget();
return { x: target.scrollLeft, y: target.scrollTop };
};
const scrollVertically = (count, smooth, repeat) => {
let target = scrollTarget();
let x = target.scrollLeft;
let y = target.scrollTop + SCROLL_DELTA_Y * count;
if (repeat && smooth) {
y = target.scrollTop + SCROLL_DELTA_Y * count * 4;
}
scroller(target, smooth, repeat).scroll(x, y);
};
const scrollHorizonally = (count, smooth, repeat) => {
let target = scrollTarget();
let x = target.scrollLeft + SCROLL_DELTA_X * count;
let y = target.scrollTop;
if (repeat && smooth) {
y = target.scrollTop + SCROLL_DELTA_Y * count * 4;
}
scroller(target, smooth, repeat).scroll(x, y);
};
const scrollPages = (count, smooth, repeat) => {
let target = scrollTarget();
let height = target.clientHeight;
let x = target.scrollLeft;
let y = target.scrollTop + height * count;
scroller(target, smooth, repeat).scroll(x, y);
};
const scrollTo = (x, y, smooth) => {
let target = scrollTarget();
scroller(target, smooth, false).scroll(x, y);
};
const scrollToTop = (smooth) => {
let target = scrollTarget();
let x = target.scrollLeft;
let y = 0;
scroller(target, smooth, false).scroll(x, y);
};
const scrollToBottom = (smooth) => {
let target = scrollTarget();
let x = target.scrollLeft;
let y = target.scrollHeight;
scroller(target, smooth, false).scroll(x, y);
};
const scrollToHome = (smooth) => {
let target = scrollTarget();
let x = 0;
let y = target.scrollTop;
scroller(target, smooth, false).scroll(x, y);
};
const scrollToEnd = (smooth) => {
let target = scrollTarget();
let x = target.scrollWidth;
let y = target.scrollTop;
scroller(target, smooth, false).scroll(x, y);
};
export {
getScroll,
scrollVertically, scrollHorizonally, scrollPages,
scrollTo,
scrollToTop, scrollToBottom, scrollToHome, scrollToEnd
};
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