CommunityRule-archival/assets/mobile-drag-drop/scroll-behaviour.js

(function (global, factory) {
	typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
	typeof define === 'function' && define.amd ? define(['exports'], factory) :
	(factory((global.MobileDragDrop = global.MobileDragDrop || {})));
}(this, (function (exports) { 'use strict';

function isTopLevelEl(el) {
    return (el === document.body || el === document.documentElement);
}
function getElementViewportOffset(el, axis) {
    var offset;
    if (isTopLevelEl(el)) {
        offset = (axis === 0) ? el.clientLeft : el.clientTop;
    }
    else {
        var bounds = el.getBoundingClientRect();
        offset = (axis === 0) ? bounds.left : bounds.top;
    }
    return offset;
}
function getElementViewportSize(el, axis) {
    var size;
    if (isTopLevelEl(el)) {
        size = (axis === 0) ? window.innerWidth : window.innerHeight;
    }
    else {
        size = (axis === 0) ? el.clientWidth : el.clientHeight;
    }
    return size;
}
function getSetElementScroll(el, axis, scroll) {
    var prop = (axis === 0) ? "scrollLeft" : "scrollTop";
    var isTopLevel = isTopLevelEl(el);
    if (arguments.length === 2) {
        if (isTopLevel) {
            return document.body[prop] || document.documentElement[prop];
        }
        return el[prop];
    }
    if (isTopLevel) {
        document.documentElement[prop] += scroll;
        document.body[prop] += scroll;
    }
    else {
        el[prop] += scroll;
    }
}
function isScrollable(el) {
    var cs = getComputedStyle(el);
    if (el.scrollHeight > el.clientHeight && (cs.overflowY === "scroll" || cs.overflowY === "auto")) {
        return true;
    }
    if (el.scrollWidth > el.clientWidth && (cs.overflowX === "scroll" || cs.overflowX === "auto")) {
        return true;
    }
    return false;
}
function findScrollableParent(el) {
    do {
        if (!el) {
            return undefined;
        }
        if (isScrollable(el)) {
            return el;
        }
        if (el === document.documentElement) {
            return null;
        }
    } while (el = el.parentNode);
    return null;
}
function determineScrollIntention(currentCoordinate, size, threshold) {
    if (currentCoordinate < threshold) {
        return -1;
    }
    else if (size - currentCoordinate < threshold) {
        return 1;
    }
    return 0;
}
function determineDynamicVelocity(scrollIntention, currentCoordinate, size, threshold) {
    if (scrollIntention === -1) {
        return Math.abs(currentCoordinate - threshold);
    }
    else if (scrollIntention === 1) {
        return Math.abs(size - currentCoordinate - threshold);
    }
    return 0;
}
function isScrollEndReached(axis, scrollIntention, scrollBounds) {
    var currentScrollOffset = (axis === 0) ? (scrollBounds.scrollX) : (scrollBounds.scrollY);
    if (scrollIntention === 1) {
        var maxScrollOffset = (axis === 0) ? (scrollBounds.scrollWidth - scrollBounds.width) : (scrollBounds.scrollHeight -
            scrollBounds.height);
        return currentScrollOffset >= maxScrollOffset;
    }
    else if (scrollIntention === -1) {
        return (currentScrollOffset <= 0);
    }
    return true;
}
var _options = {
    threshold: 75,
    velocityFn: function (velocity, threshold) {
        var multiplier = velocity / threshold;
        var easeInCubic = multiplier * multiplier * multiplier;
        return easeInCubic * threshold;
    }
};
var _scrollIntentions = {
    horizontal: 0,
    vertical: 0
};
var _dynamicVelocity = {
    x: 0,
    y: 0
};
var _scrollAnimationFrameId;
var _currentCoordinates;
var _hoveredElement;
var _scrollableParent;
var _translateDragImageFn;
function handleDragImageTranslateOverride(event, currentCoordinates, hoveredElement, translateDragImageFn) {
    _currentCoordinates = currentCoordinates;
    _translateDragImageFn = translateDragImageFn;
    if (_hoveredElement !== hoveredElement) {
        _hoveredElement = hoveredElement;
        _scrollableParent = findScrollableParent(_hoveredElement);
    }
    var performScrollAnimation = updateScrollIntentions(_currentCoordinates, _scrollableParent, _options.threshold, _scrollIntentions, _dynamicVelocity);
    if (performScrollAnimation) {
        scheduleScrollAnimation();
    }
    else if (!!_scrollAnimationFrameId) {
        window.cancelAnimationFrame(_scrollAnimationFrameId);
        _scrollAnimationFrameId = null;
    }
}
function scheduleScrollAnimation() {
    if (!!_scrollAnimationFrameId) {
        return;
    }
    _scrollAnimationFrameId = window.requestAnimationFrame(scrollAnimation);
}
function scrollAnimation() {
    var scrollDiffX = 0, scrollDiffY = 0, isTopLevel = isTopLevelEl(_scrollableParent);
    if (_scrollIntentions.horizontal !== 0) {
        scrollDiffX = Math.round(_options.velocityFn(_dynamicVelocity.x, _options.threshold) * _scrollIntentions.horizontal);
        getSetElementScroll(_scrollableParent, 0, scrollDiffX);
    }
    if (_scrollIntentions.vertical !== 0) {
        scrollDiffY = Math.round(_options.velocityFn(_dynamicVelocity.y, _options.threshold) * _scrollIntentions.vertical);
        getSetElementScroll(_scrollableParent, 1, scrollDiffY);
    }
    if (isTopLevel) {
        _translateDragImageFn(scrollDiffX, scrollDiffY);
    }
    else {
        _translateDragImageFn(0, 0);
    }
    _scrollAnimationFrameId = null;
    if (updateScrollIntentions(_currentCoordinates, _scrollableParent, _options.threshold, _scrollIntentions, _dynamicVelocity)) {
        scheduleScrollAnimation();
    }
}
function updateScrollIntentions(currentCoordinates, scrollableParent, threshold, scrollIntentions, dynamicVelocity) {
    if (!currentCoordinates || !scrollableParent) {
        return false;
    }
    var scrollableParentBounds = {
        x: getElementViewportOffset(scrollableParent, 0),
        y: getElementViewportOffset(scrollableParent, 1),
        width: getElementViewportSize(scrollableParent, 0),
        height: getElementViewportSize(scrollableParent, 1),
        scrollX: getSetElementScroll(scrollableParent, 0),
        scrollY: getSetElementScroll(scrollableParent, 1),
        scrollWidth: scrollableParent.scrollWidth,
        scrollHeight: scrollableParent.scrollHeight
    };
    var currentCoordinatesOffset = {
        x: currentCoordinates.x - scrollableParentBounds.x,
        y: currentCoordinates.y - scrollableParentBounds.y
    };
    scrollIntentions.horizontal = determineScrollIntention(currentCoordinatesOffset.x, scrollableParentBounds.width, threshold);
    scrollIntentions.vertical = determineScrollIntention(currentCoordinatesOffset.y, scrollableParentBounds.height, threshold);
    if (scrollIntentions.horizontal && isScrollEndReached(0, scrollIntentions.horizontal, scrollableParentBounds)) {
        scrollIntentions.horizontal = 0;
    }
    else if (scrollIntentions.horizontal) {
        dynamicVelocity.x = determineDynamicVelocity(scrollIntentions.horizontal, currentCoordinatesOffset.x, scrollableParentBounds.width, threshold);
    }
    if (scrollIntentions.vertical && isScrollEndReached(1, scrollIntentions.vertical, scrollableParentBounds)) {
        scrollIntentions.vertical = 0;
    }
    else if (scrollIntentions.vertical) {
        dynamicVelocity.y = determineDynamicVelocity(scrollIntentions.vertical, currentCoordinatesOffset.y, scrollableParentBounds.height, threshold);
    }
    return !!(scrollIntentions.horizontal || scrollIntentions.vertical);
}
var scrollBehaviourDragImageTranslateOverride = handleDragImageTranslateOverride;

exports.scrollBehaviourDragImageTranslateOverride = scrollBehaviourDragImageTranslateOverride;

Object.defineProperty(exports, '__esModule', { value: true });

})));
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