/**
* @file
* Manages elements that can offset the size of the viewport.
*
* Measures and reports viewport offset dimensions from elements like the
* toolbar that can potentially displace the positioning of other elements.
*/
/**
* @typedef {object} Drupal~displaceOffset
*
* @prop {number} top
* @prop {number} left
* @prop {number} right
* @prop {number} bottom
*/
/**
* Triggers when layout of the page changes.
*
* This is used to position fixed element on the page during page resize and
* Toolbar toggling.
*
* @event drupalViewportOffsetChange
*/
(function($, Drupal, debounce) {
/**
* @name Drupal.displace.offsets
*
* @type {Drupal~displaceOffset}
*/
let offsets = {
top: 0,
right: 0,
bottom: 0,
left: 0,
};
/**
* Calculates displacement for element based on its dimensions and placement.
*
* @param {HTMLElement} el
* The jQuery element whose dimensions and placement will be measured.
*
* @param {string} edge
* The name of the edge of the viewport that the element is associated
* with.
*
* @return {number}
* The viewport displacement distance for the requested edge.
*/
function getRawOffset(el, edge) {
const $el = $(el);
const documentElement = document.documentElement;
let displacement = 0;
const horizontal = edge === 'left' || edge === 'right';
// Get the offset of the element itself.
let placement = $el.offset()[horizontal ? 'left' : 'top'];
// Subtract scroll distance from placement to get the distance
// to the edge of the viewport.
placement -=
window[`scroll${horizontal ? 'X' : 'Y'}`] ||
document.documentElement[`scroll${horizontal ? 'Left' : 'Top'}`] ||
0;
// Find the displacement value according to the edge.
switch (edge) {
// Left and top elements displace as a sum of their own offset value
// plus their size.
case 'top':
// Total displacement is the sum of the elements placement and size.
displacement = placement + $el.outerHeight();
break;
case 'left':
// Total displacement is the sum of the elements placement and size.
displacement = placement + $el.outerWidth();
break;
// Right and bottom elements displace according to their left and
// top offset. Their size isn't important.
case 'bottom':
displacement = documentElement.clientHeight - placement;
break;
case 'right':
displacement = documentElement.clientWidth - placement;
break;
default:
displacement = 0;
}
return displacement;
}
/**
* Gets a specific edge's offset.
*
* Any element with the attribute data-offset-{edge} e.g. data-offset-top will
* be considered in the viewport offset calculations. If the attribute has a
* numeric value, that value will be used. If no value is provided, one will
* be calculated using the element's dimensions and placement.
*
* @function Drupal.displace.calculateOffset
*
* @param {string} edge
* The name of the edge to calculate. Can be 'top', 'right',
* 'bottom' or 'left'.
*
* @return {number}
* The viewport displacement distance for the requested edge.
*/
function calculateOffset(edge) {
let edgeOffset = 0;
const displacingElements = document.querySelectorAll(
`[data-offset-${edge}]`,
);
const n = displacingElements.length;
for (let i = 0; i < n; i++) {
const el = displacingElements[i];
// If the element is not visible, do consider its dimensions.
if (el.style.display === 'none') {
continue;
}
// If the offset data attribute contains a displacing value, use it.
let displacement = parseInt(el.getAttribute(`data-offset-${edge}`), 10);
// If the element's offset data attribute exits
// but is not a valid number then get the displacement
// dimensions directly from the element.
// eslint-disable-next-line no-restricted-globals
if (isNaN(displacement)) {
displacement = getRawOffset(el, edge);
}
// If the displacement value is larger than the current value for this
// edge, use the displacement value.
edgeOffset = Math.max(edgeOffset, displacement);
}
return edgeOffset;
}
/**
* Determines the viewport offsets.
*
* @return {Drupal~displaceOffset}
* An object whose keys are the for sides an element -- top, right, bottom
* and left. The value of each key is the viewport displacement distance for
* that edge.
*/
function calculateOffsets() {
return {
top: calculateOffset('top'),
right: calculateOffset('right'),
bottom: calculateOffset('bottom'),
left: calculateOffset('left'),
};
}
/**
* Informs listeners of the current offset dimensions.
*
* @function Drupal.displace
*
* @prop {Drupal~displaceOffset} offsets
*
* @param {bool} [broadcast]
* When true or undefined, causes the recalculated offsets values to be
* broadcast to listeners.
*
* @return {Drupal~displaceOffset}
* An object whose keys are the for sides an element -- top, right, bottom
* and left. The value of each key is the viewport displacement distance for
* that edge.
*
* @fires event:drupalViewportOffsetChange
*/
function displace(broadcast) {
offsets = calculateOffsets();
Drupal.displace.offsets = offsets;
if (typeof broadcast === 'undefined' || broadcast) {
$(document).trigger('drupalViewportOffsetChange', offsets);
}
return offsets;
}
/**
* Registers a resize handler on the window.
*
* @type {Drupal~behavior}
*/
Drupal.behaviors.drupalDisplace = {
attach() {
// Mark this behavior as processed on the first pass.
if (this.displaceProcessed) {
return;
}
this.displaceProcessed = true;
$(window).on('resize.drupalDisplace', debounce(displace, 200));
},
};
/**
* Assign the displace function to a property of the Drupal global object.
*
* @ignore
*/
Drupal.displace = displace;
$.extend(Drupal.displace, {
/**
* Expose offsets to other scripts to avoid having to recalculate offsets.
*
* @ignore
*/
offsets,
/**
* Expose method to compute a single edge offsets.
*
* @ignore
*/
calculateOffset,
});
})(jQuery, Drupal, Drupal.debounce);