WebCompDev / COMPONENTS

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  This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
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  <link rel="import" href="../polymer/polymer.html">
  
  <script>
  

    Polymer.IronOverlayManager = (function() {

      var overlays = [];
      var DEFAULT_Z = 10;
      var backdrops = [];

  
      // track overlays for z-index and focus managemant

      function addOverlay(overlay) {
        var z0 = currentOverlayZ();
        overlays.push(overlay);
        var z1 = currentOverlayZ();
        if (z1 <= z0) {
          applyOverlayZ(overlay, z0);

        }

      }

      function removeOverlay(overlay) {
        var i = overlays.indexOf(overlay);

        if (i >= 0) {

          overlays.splice(i, 1);
          setZ(overlay, '');

        }

      }
  
      function applyOverlayZ(overlay, aboveZ) {
        setZ(overlay, aboveZ + 2);
      }

      function setZ(element, z) {
        element.style.zIndex = z;
      }
  
      function currentOverlay() {
        var i = overlays.length - 1;
        while (overlays[i] && !overlays[i].opened) {

          --i;
        }

        return overlays[i];
      }

      function currentOverlayZ() {
        var z;
        var current = currentOverlay();

        if (current) {
          var z1 = window.getComputedStyle(current).zIndex;
          if (!isNaN(z1)) {
            z = Number(z1);
          }
        }

        return z || DEFAULT_Z;
      }
  
      function focusOverlay() {
        var current = currentOverlay();

        // We have to be careful to focus the next overlay _after_ any current
        // transitions are complete (due to the state being toggled prior to the
        // transition). Otherwise, we risk infinite recursion when a transitioning
        // (closed) overlay becomes the current overlay.
        //
        // NOTE: We make the assumption that any overlay that completes a transition
        // will call into focusOverlay to kick the process back off. Currently:
        // transitionend -> _applyFocus -> focusOverlay.
        if (current && !current.transitioning) {
          current._applyFocus();
        }

      }

      function trackBackdrop(element) {

        // backdrops contains the overlays with a backdrop that are currently
        // visible
        if (element.opened) {

          backdrops.push(element);

        } else {

          var index = backdrops.indexOf(element);

          if (index >= 0) {

            backdrops.splice(index, 1);

          }
        }

      }

      function getBackdrops() {
        return backdrops;

      }
  

      return {
        addOverlay: addOverlay,
        removeOverlay: removeOverlay,
        currentOverlay: currentOverlay,
        currentOverlayZ: currentOverlayZ,
        focusOverlay: focusOverlay,
        trackBackdrop: trackBackdrop,
        getBackdrops: getBackdrops
      };
  
    })();

  
  </script>