b38dea0597
Share Gaia assets and adapters, keep private profiles and development documents local, and update both public READMEs.
44 lines
1.2 KiB
JavaScript
44 lines
1.2 KiB
JavaScript
/* exported StickyHeader */
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function StickyHeader(scrollable, sticky) {
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'use strict';
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var headers = scrollable.getElementsByTagName('header');
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var stickyPosition;
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var stickyStyle = sticky.style;
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this._throttledRefresh = function() {
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var display = false;
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if (stickyPosition === undefined) {
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stickyPosition = sticky.offsetHeight + sticky.offsetTop;
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}
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for (var i = 1, length = headers.length; i < length; i++) {
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if (headers[i].offsetTop - scrollable.scrollTop > stickyPosition) {
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// While reflecting a header, make sure to not reflect a header
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// that is not displayed.
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var lookupIndex = 1;
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var header = headers[i - lookupIndex];
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while (header && header.offsetHeight === 0) {
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lookupIndex++;
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header = headers[i - lookupIndex];
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}
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stickyStyle.backgroundImage = '-moz-element(#' + header.id + ')';
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display = true;
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break;
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}
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}
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sticky.classList.toggle('has-content', display);
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this.throttle = null;
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}.bind(this);
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this.refresh = function() {
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if (!this.throttle) {
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this.throttle = setTimeout(this._throttledRefresh, 0);
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}
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}.bind(this);
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scrollable.addEventListener('scroll', this.refresh);
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}
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