420 lines
No EOL
16 KiB
JavaScript
420 lines
No EOL
16 KiB
JavaScript
/**
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* This plugin is used to fix elements to the top of the page, if the element
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* would have been scrolled out of view, vertically; however, it does allow the
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* element to continue to move left or right with the horizontal scroll.
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*
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* Given an option marginTop, the element will stop moving vertically upward
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* once the vertical scroll has reached the target position; but, the element
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* will still move horizontally as the page is scrolled left or right. Once the
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* page has been scrolled back down passed the target position, the element will
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* be restored to its original position on the page.
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*
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* This plugin has been tested in Firefox 3+, Google Chrome 10+, Safari 5+,
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* and Internet Explorer 8/9.
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*/
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(function($) {
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$.ScrollToFixed = function(el, options) {
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// To avoid scope issues, use 'base' instead of 'this' to reference this
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// class from internal events and functions.
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var base = this;
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// Access to jQuery and DOM versions of element.
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base.$el = $(el);
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base.el = el;
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// Add a reverse reference to the DOM object.
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base.$el.data("ScrollToFixed", base);
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// A flag so we know if the scroll has been reset.
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var isReset = false;
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// The element that was given to us to fix if scrolled above the top of
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// the page.
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var target = base.$el;
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var position;
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// The offset top of the element when resetScroll was called. This is
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// used to determine if we have scrolled past the top of the element.
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var offsetTop = 0;
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// The offset left of the element when resetScroll was called. This is
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// used to move the element left or right relative to the horizontal
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// scroll.
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var offsetLeft = 0;
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var originalOffsetLeft = -1;
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// This last offset used to move the element horizontally. This is used
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// to determine if we need to move the element because we would not want
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// to do that for no reason.
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var lastOffsetLeft = -1;
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// This is the element used to fill the void left by the target element
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// when it goes fixed; otherwise, everything below it moves up the page.
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var spacer = null;
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var spacerClass;
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// Capture the original offsets for the target element. This needs to be
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// called whenever the page size changes or when the page is first
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// scrolled. For some reason, calling this before the page is first
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// scrolled causes the element to become fixed too late.
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function resetScroll() {
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// Set the element to it original positioning.
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setUnfixed();
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// Reset the last offset used to determine if the page has moved
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// horizontally.
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lastOffsetLeft = -1;
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// Capture the offset top of the target element.
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offsetTop = target.offset().top;
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// Capture the offset left of the target element.
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offsetLeft = target.offset().left + (target.offset().left - target.position().left);
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if (originalOffsetLeft == -1) {
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originalOffsetLeft = offsetLeft;
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}
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position = target.css('position');
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// Set that this has been called at least once.
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isReset = true;
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if (base.options.bottom != -1) {
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setFixed();
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}
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}
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function getLimit() {
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var limit = base.options.limit;
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if (!limit) return 0;
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if (typeof(limit) === 'function') {
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return limit();
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}
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return limit;
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}
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// Returns whether the target element is fixed or not.
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function isFixed() {
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return position === 'fixed';
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}
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// Returns whether the target element is absolute or not.
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function isAbsolute() {
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return position === 'absolute';
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}
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function isUnfixed() {
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return !(isFixed() || isAbsolute());
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}
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// Sets the target element to fixed. Also, sets the spacer to fill the
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// void left by the target element.
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function setFixed() {
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// Only fix the target element and the spacer if we need to.
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if (!isFixed()) {
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// Set the spacer to fill the height and width of the target
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// element, then display it.
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spacer.css({
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'display' : target.css('display'),
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'width' : target.outerWidth(true),
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'height' : target.outerHeight(true),
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'float' : target.css('float')
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});
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// Set the target element to fixed and set its width so it does
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// not fill the rest of the page horizontally. Also, set its top
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// to the margin top specified in the options.
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target.css({
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'width' : target.width(),
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'position' : 'fixed',
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'top' : base.options.bottom == -1?getMarginTop():'',
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'bottom' : base.options.bottom == -1?'':base.options.bottom
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});
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position = 'fixed';
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}
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}
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function setAbsolute() {
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target.css({
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'width' : target.width(),
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'position' : 'absolute',
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'top' : getLimit(),
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'left' : offsetLeft
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});
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position = 'absolute';
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}
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// Sets the target element back to unfixed. Also, hides the spacer.
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function setUnfixed() {
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// Only unfix the target element and the spacer if we need to.
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if (!isUnfixed()) {
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lastOffsetLeft = -1;
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// Hide the spacer now that the target element will fill the
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// space.
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spacer.css('display', 'none');
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// Remove the style attributes that were added to the target.
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// This will reverse the target back to the its original style.
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target.css({
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'width' : '',
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'position' : '',
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'left' : '',
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'top' : ''
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});
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position = null;
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}
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}
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// Moves the target element left or right relative to the horizontal
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// scroll position.
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function setLeft(x) {
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// Only if the scroll is not what it was last time we did this.
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if (x != lastOffsetLeft) {
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// Move the target element horizontally relative to its original
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// horizontal position.
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target.css('left', offsetLeft - x);
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// Hold the last horizontal position set.
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lastOffsetLeft = x;
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}
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}
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function getMarginTop() {
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return base.options.marginTop;
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}
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// Checks to see if we need to do something based on new scroll position
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// of the page.
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function checkScroll() {
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var wasReset = isReset;
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// If resetScroll has not yet been called, call it. This only
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// happens once.
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if (!isReset) {
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resetScroll();
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}
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// Grab the current horizontal scroll position.
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var x = $(window).scrollLeft();
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// Grab the current vertical scroll position.
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var y = $(window).scrollTop();
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// Get the limit, if there is one.
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var limit = getLimit();
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// If the vertical scroll position, plus the optional margin, would
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// put the target element at the specified limit, set the target
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// element to absolute.
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if (base.options.minWidth && $(window).width() < base.options.minWidth) {
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if (!isUnfixed() || !wasReset) {
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postPosition();
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target.trigger('preUnfixed');
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setUnfixed();
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target.trigger("unfixed");
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}
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} else if (base.options.bottom == -1) {
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// If the vertical scroll position, plus the optional margin, would
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// put the target element at the specified limit, set the target
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// element to absolute.
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if (limit > 0 && y >= limit - getMarginTop()) {
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if (!isAbsolute() || !wasReset) {
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postPosition();
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target.trigger('preAbsolute');
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setAbsolute();
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target.trigger('unfixed');
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}
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// If the vertical scroll position, plus the optional margin, would
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// put the target element above the top of the page, set the target
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// element to fixed.
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} else if (y >= offsetTop - getMarginTop()) {
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if (!isFixed() || !wasReset) {
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postPosition();
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target.trigger('preFixed');
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// Set the target element to fixed.
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setFixed();
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// Reset the last offset left because we just went fixed.
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lastOffsetLeft = -1;
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target.trigger('fixed');
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}
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// If the page has been scrolled horizontally as well, move the
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// target element accordingly.
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setLeft(x);
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} else {
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// Set the target element to unfixed, placing it where it was
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// before.
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if (!isUnfixed() || !wasReset) {
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postPosition();
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target.trigger('preUnfixed');
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setUnfixed();
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target.trigger("unfixed");
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}
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}
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} else {
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if (limit > 0) {
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if (y + $(window).height() - target.outerHeight(true) >= limit - getMarginTop()) {
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if (isFixed()) {
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postPosition();
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target.trigger('preUnfixed');
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setUnfixed();
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target.trigger("unfixed");
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}
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} else {
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if (!isFixed()) {
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postPosition();
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target.trigger('preFixed');
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setFixed();
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}
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setLeft(x);
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target.trigger("fixed");
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}
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} else {
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setLeft(x);
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}
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}
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}
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function postPosition() {
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var position = target.css('position');
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if (position == 'absolute') {
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target.trigger('postAbsolute');
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} else if (position == 'fixed') {
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target.trigger('postFixed');
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} else {
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target.trigger('postUnfixed');
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}
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}
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var windowResize = function(event) {
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isReset = false;
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checkScroll();
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}
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var windowScroll = function(event) {
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checkScroll();
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}
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// Initializes this plugin. Captures the options passed in, turns this
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// off for iOS, adds the spacer, and binds to the window scroll and
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// resize events.
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base.init = function() {
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// Capture the options for this plugin.
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base.options = $
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.extend({}, $.ScrollToFixed.defaultOptions, options);
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// Turn off this functionality for iOS devices until we figure out
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// what to do with them, or until iOS5 comes out which is supposed
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// to support position:fixed.
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if (navigator.platform === 'iPad' || navigator.platform === 'iPhone' || navigator.platform === "iPod") {
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if (!navigator.userAgent.match(/OS 5_.*\ like Mac OS X/i)) {
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return;
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}
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}
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// Put the target element on top of everything that could be below
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// it. This reduces flicker when the target element is transitioning
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// to fixed.
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base.$el.css('z-index', base.options.zIndex);
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// Create a spacer element to fill the void left by the target
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// element when it goes fixed.
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spacer = $('<div />');
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position = target.css('position');
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// Place the spacer right after the target element.
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if (isUnfixed()) base.$el.after(spacer);
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// Reset the target element offsets when the window is resized, then
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// check to see if we need to fix or unfix the target element.
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$(window).bind('resize.ScrollToFixed', windowResize);
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// When the window scrolls, check to see if we need to fix or unfix
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// the target element.
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$(window).bind('scroll.ScrollToFixed', windowScroll);
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if (base.options.preFixed) {
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target.bind('preFixed.ScrollToFixed', base.options.preFixed);
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}
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if (base.options.postFixed) {
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target.bind('postFixed.ScrollToFixed', base.options.postFixed);
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}
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if (base.options.preUnfixed) {
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target.bind('preUnfixed.ScrollToFixed', base.options.preUnfixed);
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}
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if (base.options.postUnfixed) {
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target.bind('postUnfixed.ScrollToFixed', base.options.postUnfixed);
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}
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if (base.options.preAbsolute) {
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target.bind('preAbsolute.ScrollToFixed', base.options.preAbsolute);
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}
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if (base.options.postAbsolute) {
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target.bind('postAbsolute.ScrollToFixed', base.options.postAbsolute);
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}
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if (base.options.fixed) {
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target.bind('fixed.ScrollToFixed', base.options.fixed);
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}
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if (base.options.unfixed) {
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target.bind('unfixed.ScrollToFixed', base.options.unfixed);
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}
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if (base.options.spacerClass) {
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spacer.addClass(base.options.spacerClass);
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}
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target.bind('resize', function() {
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spacer.height(target.height());
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});
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target.bind('scroll.ScrollToFixed', function() {
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setUnfixed();
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checkScroll();
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});
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target.bind('remove.ScrollToFixed', function() {
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setUnfixed();
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$(window).unbind('resize', windowResize);
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$(window).unbind('scroll', windowScroll);
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target.unbind('.ScrollToFixed');
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});
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if (base.options.bottom != -1) {
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if (!isFixed()) {
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postPosition();
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target.trigger('preFixed.ScrollToFixed');
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setFixed();
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}
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}
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};
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// Initialize the plugin.
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base.init();
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};
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// Sets the option defaults.
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$.ScrollToFixed.defaultOptions = {
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marginTop : 0,
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limit : 0,
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bottom : -1,
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zIndex : 1000
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};
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// Returns enhanced elements that will fix to the top of the page when the
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// page is scrolled.
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$.fn.scrollToFixed = function(options) {
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return this.each(function() {
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(new $.ScrollToFixed(this, options));
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});
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};
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})(jQuery); |