--- /dev/null
+/**
+ * @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,
+ };
+
+ /**
+ * 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));
+ },
+ };
+
+ /**
+ * 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 = Drupal.displace.offsets = calculateOffsets();
+ if (typeof broadcast === 'undefined' || broadcast) {
+ $(document).trigger('drupalViewportOffsetChange', offsets);
+ }
+ return offsets;
+ }
+
+ /**
+ * Determines the viewport offsets.
+ *
+ * @return {Drupal~displaceOffset}
+ * An object whose keys are the for sides an element -- top, right, bottom
+ * and left. The value of each key is the viewport displacement distance for
+ * that edge.
+ */
+ function calculateOffsets() {
+ return {
+ top: calculateOffset('top'),
+ right: calculateOffset('right'),
+ bottom: calculateOffset('bottom'),
+ left: calculateOffset('left'),
+ };
+ }
+
+ /**
+ * Gets a specific edge's offset.
+ *
+ * Any element with the attribute data-offset-{edge} e.g. data-offset-top will
+ * be considered in the viewport offset calculations. If the attribute has a
+ * numeric value, that value will be used. If no value is provided, one will
+ * be calculated using the element's dimensions and placement.
+ *
+ * @function Drupal.displace.calculateOffset
+ *
+ * @param {string} edge
+ * The name of the edge to calculate. Can be 'top', 'right',
+ * 'bottom' or 'left'.
+ *
+ * @return {number}
+ * The viewport displacement distance for the requested edge.
+ */
+ function calculateOffset(edge) {
+ let edgeOffset = 0;
+ const displacingElements = document.querySelectorAll(`[data-offset-${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.
+ 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;
+ }
+
+ /**
+ * 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;
+ }
+
+ /**
+ * 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));
projects / yaffs-website / blobdiff