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+// $Id$
+(function ($) {
+
+/**
+ * Provides a generic method to position elements fixed to the viewport.
+ *
+ * Fixed positioning (CSS declaration position:fixed) is done relatively to the
+ * viewport. This makes it hard to position multiple fixed positioned element
+ * relative to each other (e.g. multiple toolbars should come after each other,
+ * not on top of each other).
+ *
+ * To position an element fixed at the top of the viewport add the class
+ * "displace-top" to that element, and to position it to the bottom of the view-
+ * port add the class "displace-bottom".
+ *
+ * When a browser doesn't support position:fixed (like IE6) the element gets
+ * positioned absolutely by default, but this can be overriden by using the
+ * "displace-unsupported" class.
+ */
+
+/**
+ * Attaches the displace behavior.
+ */
+Drupal.behaviors.displace = {
+  attach: function (context, settings) {
+    // Test for position:fixed support as IE6 does not.
+    // http://yura.thinkweb2.com/cft/#IS_POSITION_FIXED_SUPPORTED
+    if (this.supported === undefined) {
+      var el = $('<div style="position:fixed;top:10px"/>').appendTo(document.body);
+      this.supported = el[0].offsetTop === 10;
+      el.remove();
+
+      if (!this.supported) {
+        $(document.documentElement).addClass('displace-unsupported');
+      }
+    }
+
+    $(document.body).once('displace', function () {
+      $(window).bind('resize.drupal-displace', function () {
+        Drupal.displace.clearCache();
+
+        $(document.body).css({
+          paddingTop: Drupal.displace.getDisplacement('top'),
+          paddingBottom: Drupal.displace.getDisplacement('bottom')
+        });
+      });
+    });
+
+    Drupal.displace.clearCache(true);
+    $(window).triggerHandler('resize');
+  }
+};
+
+/**
+ * The displace object.
+ */
+Drupal.displace = Drupal.displace || {};
+
+Drupal.displace.elements = [];
+Drupal.displace.displacement = [];
+
+/**
+ * Get all displaced elements of given region.
+ *
+ * @param region
+ *   Region name. Either "top" or "bottom".
+ *
+ * @return
+ *   jQuery object containing all displaced elements of given region.
+ */
+Drupal.displace.getDisplacedElements = function (region) {
+  if (!this.elements[region]) {
+    this.elements[region] = $('.displace-' + region);
+  }
+  return this.elements[region];
+};
+
+/**
+ * Get the total displacement of given region.
+ *
+ * @param region
+ *   Region name. Either "top" or "bottom".
+ *
+ * @return
+ *   The total displacement of given region in pixels.
+ */
+Drupal.displace.getDisplacement = function (region) {
+  if (!this.displacement[region]) {
+    var offset = 0;
+    var height = 0;
+    this.getDisplacedElements(region).each(function () {
+      offset = offset + height;
+      height = $(this).css(region, offset).outerHeight();
+
+      // In IE, Shadow filter adds some extra height, so we need to remove it
+      // from the returned height.
+      if (this.filters && this.filters.length && this.filters.item('DXImageTransform.Microsoft.Shadow')) {
+        height -= this.filters.item('DXImageTransform.Microsoft.Shadow').strength;
+      }
+    });
+
+    // Use offset of latest displaced element as the total displacement.
+    this.displacement[region] = offset + height;
+  }
+
+  return this.displacement[region];
+};
+
+/**
+ * Clear cache.
+ *
+ * @param selectorCache
+ *   Boolean whether to also clear the selector cache.
+ */
+Drupal.displace.clearCache = function (selectorCache) {
+  if (selectorCache) {
+    this.elements = [];
+  }
+  this.displacement = [];
+};
+
+})(jQuery);