Files
notifications-admin/app/assets/javascripts/stick-to-window-when-scrolling.js
2019-02-13 14:49:42 +00:00

764 lines
22 KiB
JavaScript

;(function (global) {
'use strict';
var $ = global.jQuery;
var GOVUK = global.GOVUK || {};
var _mode = 'default';
// Object collecting together methods for dealing with marking the edge of a sticky, or group of
// sticky elements (as seen in dialog mode)
var oppositeEdge = {
_classes: {
'top': 'content-fixed__top',
'bottom': 'content-fixed__bottom'
},
_getClassForEdge: function (edge) {
return this._classes[edge];
},
mark: function (sticky) {
var edgeClass = this._getClassForEdge(sticky.edge);
var els;
if (_mode === 'dialog') {
els = [dialog.getElementAtOppositeEnd(sticky)];
} else {
els = sticky._els;
}
els = $.grep(els, function (el) { return el.isStuck(); });
$.each(els, function (i, el) {
el.$fixedEl.addClass(edgeClass);
});
},
unmark: function (sticky) {
var edgeClass = this._getClassForEdge(sticky.edge);
$.each(sticky._els, function (i, el) {
el.$fixedEl.removeClass(edgeClass);
});
}
};
// Constructor for objects holding data for each element to have sticky behaviour
var StickyElement = function ($el, sticky) {
this._sticky = sticky;
this.$fixedEl = $el;
this._initialFixedClass = 'content-fixed-onload';
this._fixedClass = 'content-fixed';
this._appliedClass = null;
this._$shim = null;
this._stopped = false;
this._hasLoaded = false;
this._canBeStuck = true;
this.verticalMargins = {
'top': parseInt(this.$fixedEl.css('margin-top'), 10),
'bottom': parseInt(this.$fixedEl.css('margin-bottom'), 10),
};
};
StickyElement.prototype._getShimCSS = function () {
return {
'width': this.horizontalSpace + 'px',
'height': this.height + 'px',
'margin-top': this.verticalMargins.top + 'px',
'margin-bottom': this.verticalMargins.bottom + 'px'
};
};
StickyElement.prototype.stickyClass = function () {
return (this._sticky._initialPositionsSet) ? this._fixedClass : this._initialFixedClass;
};
StickyElement.prototype.appliedClass = function () {
return this._appliedClass;
};
StickyElement.prototype.removeStickyClasses = function (sticky) {
this.$fixedEl.removeClass([
this._initialFixedClass,
this._fixedClass
].join(' '));
};
StickyElement.prototype.isStuck = function () {
return this._appliedClass !== null;
};
StickyElement.prototype.stick = function (sticky) {
this._appliedClass = this.stickyClass();
this.$fixedEl.addClass(this._appliedClass);
this._hasBeenCalled = true;
};
StickyElement.prototype.release = function (sticky) {
this._appliedClass = null;
this.removeStickyClasses(sticky);
this._hasBeenCalled = true;
};
// When a sticky element is moved into the 'stuck' state, a shim is inserted into the
// page to preserve the space the element occupies in the flow.
StickyElement.prototype.addShim = function (position) {
this._$shim = $('<div class="shim">&nbsp</div>');
this._$shim.css(this._getShimCSS());
this.$fixedEl[position](this._$shim);
};
StickyElement.prototype.removeShim = function () {
if (this._$shim !== null) {
this._$shim.remove();
this._$shim = null;
}
};
// Changes to the dimensions of a sticky element with a shim need to be passed on to the shim
StickyElement.prototype.updateShim = function () {
if (this._$shim) {
this._$shim.css(this._getShimCSS());
}
};
StickyElement.prototype.stop = function () {
this._stopped = true;
};
StickyElement.prototype.unstop = function () {
this._stopped = false;
};
StickyElement.prototype.isStopped = function () {
return this._stopped;
};
StickyElement.prototype.isInPage = function () {
var node = this.$fixedEl.get(0);
return (node === document.body) ? false : document.body.contains(node);
};
StickyElement.prototype.canBeStuck = function (val) {
if (val !== undefined) {
this._canBeStuck = val;
} else {
return this._canBeStuck;
}
};
StickyElement.prototype.hasLoaded = function (val) {
if (val !== undefined) {
this._hasLoaded = val;
} else {
return this._hasLoaded;
}
};
// Object collecting together methods for treating sticky elements as if they
// were wrapped by a dialog component
var dialog = {
hasResized: false,
spaceBetweenStickys: 40,
// we add padding of 20px around each sticky to give some space between it and the rest of the page
// this shouldn't apply between stickys in a stack
// (the in-page CSS handles this by each subsequent sticky in a sequence having margin: -40px)
_getPaddingBetweenEls: function (els) {
if (els.length <= 1) { return 0; }
return (els.length - 1) * this.spaceBetweenStickys;
},
_getTotalHeight: function (els) {
var reducer = function (accumulator, currentValue) {
return accumulator + currentValue;
};
var combinedHeight = $.map(els, function (el) { return el.height; }).reduce(reducer);
return combinedHeight - this._getPaddingBetweenEls(els);
},
_elsThatCanBeStuck: function (els) {
return $.grep(els, function (el) { return el.canBeStuck(); });
},
getOffsetFromEdge: function (el, sticky) {
var els = this._elsThatCanBeStuck(sticky._els).slice();
var elIdx;
// els must be arranged furtherest from window edge is stuck to first
// default direction is order in document
if (sticky.edge === 'top') {
els.reverse();
}
elIdx = els.indexOf(el);
// if next to window edge the dialog is stuck to, no offset
if (elIdx === (els.length - 1)) { return 0; }
// make els all those from this one to the window edge
els = els.slice(elIdx + 1);
// remove the space between those els and the one on the edge
return this._getTotalHeight(els) - this.spaceBetweenStickys;
},
getOffsetFromEnd: function (el, sticky) {
var els = this._elsThatCanBeStuck(sticky._els).slice();
var elIdx;
// els must be arranged furtherest from window edge is stuck to first
// default direction is order in document
if (sticky.edge === 'bottom') {
els.reverse();
}
elIdx = els.indexOf(el);
// if next to opposite edge to the one the dialog is stuck to, no offset
if (elIdx === (els.length - 1)) { return 0; }
// make els all those from this one to the window edge
els = els.slice(elIdx + 1);
return this._getTotalHeight(els) - this.spaceBetweenStickys;
},
// checks total height of all this._sticky elements against a height
// unsticks each that won't fit and marks them as unstickable
fitToHeight: function (sticky) {
var self = this;
var els = sticky._els.slice();
var height = sticky.getWindowDimensions().height;
var totalStickyHeight = function () {
return self._getTotalHeight(self._elsThatCanBeStuck(els));
};
var dialogFitsHeight = function () {
return totalStickyHeight() <= height;
};
// els must be arranged furtherest from window edge is stuck to first
// default direction is order in document
if (sticky.edge === 'top') {
els.reverse();
}
// reset elements
$.each(els, function (i, el) { el.canBeStuck(true); });
while (self._elsThatCanBeStuck(els).length && !dialogFitsHeight()) {
var currentEl = self._elsThatCanBeStuck(els)[0];
sticky.reset(currentEl);
currentEl.canBeStuck(false);
if (!self.hasResized) { self.hasResized = true; }
}
},
getElementAtStickyEdge: function (sticky) {
var els = this._elsThatCanBeStuck(sticky._els);
var idx = (sticky.edge === 'top') ? 0 : els.length - 1;
return els[idx];
},
// get element at the end opposite the sticky edge
getElementAtOppositeEnd: function (sticky) {
var els = this._elsThatCanBeStuck(sticky._els);
var idx = (sticky.edge === 'top') ? els.length - 1 : 0;
return els[idx];
},
getInPageEdgePosition: function (sticky) {
return this.getElementAtStickyEdge(sticky).inPageEdgePosition;
},
getHeight: function (els) {
return this._getTotalHeight(this._elsThatCanBeStuck(els));
},
adjustForResize: function (sticky) {
var windowHeight = sticky.getWindowDimensions().height;
if (sticky.edge === 'top') {
$(window).scrollTop(this.getInPageEdgePosition(sticky));
} else {
$(window).scrollTop(this.getInPageEdgePosition(sticky) - windowHeight);
}
this.hasResized = false;
},
releaseEl: function (el, sticky) {
el.$fixedEl.css(sticky.edge, '');
}
};
// Constructor for objects collecting together all generic behaviour for controlling the state of
// sticky elements
var Sticky = function (selector) {
this._hasScrolled = false;
this._scrollTimeout = false;
this._windowHasResized = false;
this._resizeTimeout = false;
this._elsLoaded = false;
this._initialPositionsSet = false;
this._els = [];
this.CSS_SELECTOR = selector;
this.STOP_PADDING = 10;
};
Sticky.prototype.setMode = function (mode) {
_mode = mode;
};
Sticky.prototype.getWindowDimensions = function () {
return {
height: $(global).height(),
width: $(global).width()
};
};
Sticky.prototype.getWindowPositions = function () {
return {
scrollTop: $(global).scrollTop()
};
};
// Change state of sticky elements based on their position relative to the window
Sticky.prototype.setElementPositions = function () {
var self = this,
windowDimensions = self.getWindowDimensions(),
windowTop = self.getWindowPositions().scrollTop,
windowPositions = {
'top': windowTop,
'bottom': windowTop + windowDimensions.height
};
var _setElementPosition = function (el) {
if (self.viewportIsWideEnough(windowDimensions.width)) {
if (self.windowNotPastScrolledFrom(windowPositions, self.getScrolledFrom(el))) {
self.reset(el);
} else { // past the point it sits in the document
if (self.windowNotPastScrollingTo(windowPositions, self.getScrollingTo(el))) {
self.stick(el);
if (el.isStopped()) {
self.unstop(el);
}
} else { // window past scrollingTo position
if (!el.isStuck()) {
self.stick(el);
}
self.stop(el);
}
}
} else {
self.reset(el);
}
};
// clean up any existing styles marking the edges of sticky elements
oppositeEdge.unmark(self);
$.each(self._els, function (i, el) {
if (el.canBeStuck()) {
_setElementPosition(el);
}
});
// add styles to mark the edge of sticky elements opposite to that stuck to the window
oppositeEdge.mark(self);
if (self._initialPositionsSet === false) { self._initialPositionsSet = true; }
};
// Store all the dimensions for a sticky element to limit DOM queries
Sticky.prototype.setElementDimensions = function (el, callback) {
var self = this;
var $el = el.$fixedEl;
var onHeightSet = function () {
// if element is shim'ed, pass changes in dimension on to the shim
if (el._$shim) {
el.updateShim();
}
if (callback !== undefined) {
callback();
}
};
this.setElWidth(el);
this.setElHeight(el, onHeightSet);
};
// Reset element to original state in the page
Sticky.prototype.reset = function (el) {
if (el.isStopped()) {
this.unstop(el);
}
if (el.isStuck()) {
this.release(el);
}
};
// Recalculate stored dimensions for all sticky elements
Sticky.prototype.recalculate = function () {
var self = this;
var onSyncComplete = function () {
self.setEvents();
if (_mode === 'dialog') {
dialog.fitToHeight(self);
if (dialog.hasResized) {
dialog.adjustForResize(self);
}
}
self.setElementPositions();
};
this.syncWithDOM(onSyncComplete);
};
Sticky.prototype.setElWidth = function (el) {
var $el = el.$fixedEl;
var width = $el.parent().width();
el.horizontalSpace = width;
// if stuck, element won't inherit width from parent so set explicitly
if (el._$shim) {
$el.width(width);
}
};
Sticky.prototype.setElHeight = function (el, callback) {
var self = this;
var $el = el.$fixedEl;
var $img = $el.find('img');
var onload = function () {
el.height = $el.outerHeight();
// if element has a shim, the shim's offset represents the element's in-page position
if (el._$shim) {
el.inPageEdgePosition = self.getInPageEdgePosition(el._$shim);
} else {
el.inPageEdgePosition = self.getInPageEdgePosition($el);
}
callback();
};
if ((!el.hasLoaded()) && ($img.length > 0)) {
var image = new global.Image();
image.onload = function () {
onload();
};
image.src = $img.attr('src');
} else {
onload();
}
};
Sticky.prototype.allElementsLoaded = function (totalEls) {
return this._els.length === totalEls;
};
Sticky.prototype.getElForNode = function (node) {
var matches = $.grep(this._els, function (el) { return el.$fixedEl.is(node); });
return !!matches.length ? matches[0] : false;
};
Sticky.prototype.add = function (el, setPositions, cb) {
var self = this;
var $el = $(el);
var onDimensionsSet;
var elObj = this.getElForNode(el);
var exists = !!elObj;
onDimensionsSet = function () {
elObj.hasLoaded(true);
// guard against adding elements already stored
if (!exists) {
self._els.push(elObj);
}
if (setPositions) {
self.setElementPositions();
}
if (cb !== undefined) {
cb();
}
};
if (!exists) {
elObj = new StickyElement($el, self);
}
self.setElementDimensions(elObj, onDimensionsSet);
};
Sticky.prototype.remove = function (el) {
if ($.inArray(el, this._els) !== -1) {
// reset DOM node to original state
this.reset(el);
// remove sticky element object
this._els = $.grep(this._els, function (_el) { return _el !== el; });
}
};
// gets all sticky elements in the DOM and removes any in this._els no longer in attached to it
Sticky.prototype.syncWithDOM = function (callback) {
var self = this;
var $els = $(self.CSS_SELECTOR);
var numOfEls = $els.length;
var onLoaded;
onLoaded = function () {
if (self._els.length === numOfEls) {
self.endOfScrollArea = self.getEndOfScrollArea();
if (callback !== undefined) {
callback();
}
}
};
// remove any els no longer in the DOM
if (this._els.length) {
$.each(this._els, function (i, el) {
if (!el.isInPage()) {
self.remove(el);
}
});
}
if (numOfEls) {
// reset flag marking page load
this._initialPositionsSet = false;
$els.each(function (i, el) {
// delay setting position until all stickys are loaded
self.add(el, false, onLoaded);
});
}
};
Sticky.prototype.init = function () {
this.recalculate();
};
Sticky.prototype.setEvents = function () {
var self = this;
// flag when scrolling takes place and check (and re-position) sticky elements relative to
// window position
if (self._scrollTimeout === false) {
$(global).scroll(function (e) { self.onScroll(); });
self._scrollTimeout = global.setInterval(function (e) { self.checkScroll(); }, 50);
}
// Recalculate all dimensions when the window resizes
if (self._resizeTimeout === false) {
$(global).resize(function (e) { self.onResize(); });
self._resizeTimeout = global.setInterval(function (e) { self.checkResize(); }, 50);
}
};
Sticky.prototype.viewportIsWideEnough = function (windowWidth) {
return windowWidth > 768;
};
Sticky.prototype.onScroll = function () {
this._hasScrolled = true;
};
Sticky.prototype.onResize = function () {
this._windowHasResized = true;
};
Sticky.prototype.checkScroll = function () {
var self = this;
if (self._hasScrolled === true) {
self._hasScrolled = false;
self.setElementPositions();
}
};
Sticky.prototype.checkResize = function () {
var self = this,
windowWidth = self.getWindowDimensions().width;
if (self._windowHasResized === true) {
self._windowHasResized = false;
$.each(self._els, function (i, el) {
if (!self.viewportIsWideEnough(windowWidth)) {
self.reset(el);
} else {
self.setElementDimensions(el);
}
});
if (self.viewportIsWideEnough(windowWidth)) {
if (_mode === 'dialog') {
dialog.fitToHeight(self);
if (dialog.hasResized) {
dialog.adjustForResize(self);
}
}
self.setElementPositions();
}
}
};
Sticky.prototype.release = function (el) {
if (el.isStuck()) {
var $el = el.$fixedEl;
el.removeStickyClasses(this);
$el.css('width', '');
// clear styles from any elements stuck while in a dialog mode
dialog.releaseEl(el, this);
el.removeShim();
el.release(this);
}
};
// Extension of sticky object to add behaviours specific to sticking to top of window
var stickAtTop = new Sticky('.js-stick-at-top-when-scrolling');
stickAtTop.edge = 'top';
// Store furthest point sticky elements are allowed
stickAtTop.getEndOfScrollArea = function () {
var footer = $('.js-footer:eq(0)');
if (footer.length === 0) {
return 0;
}
return footer.offset().top - this.STOP_PADDING;
};
// position of the bottom edge when in the page flow
stickAtTop.getInPageEdgePosition = function ($el) {
return $el.offset().top;
};
stickAtTop.getScrolledFrom = function (el) {
if (_mode === 'dialog') {
return dialog.getInPageEdgePosition(this);
} else {
return el.inPageEdgePosition;
}
};
stickAtTop.getScrollingTo = function (el) {
var height = el.height;
if (_mode === 'dialog') {
height = dialog.getHeight(this._els);
}
return this.endOfScrollArea - height;
};
stickAtTop.getStoppingPosition = function (el) {
var offset = 0;
if (_mode === 'dialog') {
offset = dialog.getOffsetFromEnd(el, this);
}
return (this.endOfScrollArea - offset) - el.height;
};
stickAtTop.windowNotPastScrolledFrom = function (windowPositions, scrolledFrom) {
return scrolledFrom > windowPositions.top;
};
stickAtTop.windowNotPastScrollingTo = function (windowPositions, scrollingTo) {
return windowPositions.top < scrollingTo;
};
stickAtTop.stick = function (el) {
if (!el.isStuck()) {
var $el = el.$fixedEl;
var offset = 0;
if (_mode === 'dialog') {
offset = dialog.getOffsetFromEdge(el, this);
}
el.addShim('before');
$el.css({
// element will be absolutely positioned so cannot rely on parent element for width
'width': $el.width() + 'px',
'top': offset + 'px'
});
el.stick(this);
}
};
stickAtTop.stop = function (el) {
if (!el.isStopped()) {
el.$fixedEl.css({
'position': 'absolute',
'top': this.getStoppingPosition(el)
});
el.stop();
}
};
stickAtTop.unstop = function (el) {
var offset = 0;
if (_mode === 'dialog') {
offset = dialog.getOffsetFromEdge(el, this);
}
el.$fixedEl.css({
'position': '',
'top': offset + 'px'
});
el.unstop();
};
// Extension of sticky object to add behaviours specific to sticking to bottom of window
var stickAtBottom = new Sticky('.js-stick-at-bottom-when-scrolling');
stickAtBottom.edge = 'bottom';
// Store furthest point sticky elements are allowed
stickAtBottom.getEndOfScrollArea = function () {
var header = $('.js-header:eq(0)');
if (header.length === 0) {
return 0;
}
return (header.offset().top + header.outerHeight()) + this.STOP_PADDING;
};
// position of the bottom edge when in the page flow
stickAtBottom.getInPageEdgePosition = function ($el) {
return $el.offset().top + $el.outerHeight();
};
stickAtBottom.getScrolledFrom = function (el) {
if (_mode === 'dialog') {
return dialog.getInPageEdgePosition(this);
} else {
return el.inPageEdgePosition;
}
};
stickAtBottom.getScrollingTo = function (el) {
var height = el.height;
if (_mode === 'dialog') {
height = dialog.getHeight(this._els);
}
return this.endOfScrollArea + height;
};
stickAtBottom.getStoppingPosition = function (el) {
var offset = 0;
if (_mode === 'dialog') {
offset = dialog.getOffsetFromEnd(el, this);
}
return this.endOfScrollArea + offset;
};
stickAtBottom.windowNotPastScrolledFrom = function (windowPositions, scrolledFrom) {
return scrolledFrom < windowPositions.bottom;
};
stickAtBottom.windowNotPastScrollingTo = function (windowPositions, scrollingTo) {
return windowPositions.bottom > scrollingTo;
};
stickAtBottom.stick = function (el) {
if (!el.isStuck()) {
var $el = el.$fixedEl;
var offset = 0;
if (_mode === 'dialog') {
offset = dialog.getOffsetFromEdge(el, this);
}
el.addShim('after');
$el.css({
// element will be absolutely positioned so cannot rely on parent element for width
'width': $el.width() + 'px',
'bottom': offset + 'px'
});
el.stick(this);
}
};
stickAtBottom.stop = function (el) {
if (!el.isStopped()) {
el.$fixedEl.css({
'position': 'absolute',
'top': this.getStoppingPosition(el),
'bottom': 'auto'
});
el.stop();
}
};
stickAtBottom.unstop = function (el) {
var offset = 0;
if (_mode === 'dialog') {
offset = dialog.getOffsetFromEdge(el, this);
}
el.$fixedEl.css({
'position': '',
'top': '',
'bottom': offset + 'px'
});
el.unstop();
};
GOVUK.stickAtTopWhenScrolling = stickAtTop;
GOVUK.stickAtBottomWhenScrolling = stickAtBottom;
global.GOVUK = GOVUK;
})(window);