Roll Polymer elements

third_party/polymer/v1_0/components-chromium/app-layout/app-box/app-box-extracted.js

+Polymer({
+      is: 'app-box',
+
+      behaviors: [
+        Polymer.AppScrollEffectsBehavior,
+        Polymer.IronResizableBehavior
+      ],
+
+      listeners: {
+        'iron-resize': '_resizeHandler'
+      },
+
+      /**
+       * The current scroll progress.
+       *
+       * @type {number}
+       */
+      _progress: 0,
+
+      attached: function() {
+        this.resetLayout();
+      },
+
+      /**
+       * Resets the layout. This method is automatically called when the element is attached to the DOM.
+       *
+       * @method resetLayout
+       */
+      resetLayout: function() {
+        this.debounce('_resetLayout', function() {
+          // noop if the box isn't in the rendered tree
+          if (this.offsetWidth === 0 && this.offsetHeight === 0) {
+            return;
+          }
+
+          var scrollTop = this._clampedScrollTop;
+          var savedDisabled = this.disabled;
+
+          this.disabled = true;
+          this._elementTop = this._getElementTop();
+          this._elementHeight = this.offsetHeight;
+          this._cachedScrollTargetHeight = this._scrollTargetHeight;
+          this._setUpEffect();
+          this._updateScrollState(scrollTop);
+          this.disabled = savedDisabled;
+        }, 1);
+      },
+
+      _getElementTop: function() {
+        var currentNode = this;
+        var top = 0;
+
+        while (currentNode && currentNode !== this.scrollTarget) {
+          top += currentNode.offsetTop;
+          currentNode = currentNode.offsetParent;
+        }
+        return top;
+      },
+
+      _updateScrollState: function(scrollTop) {
+        if (this.isOnScreen()) {
+          var viewportTop = this._elementTop - scrollTop;
+          this._progress = 1 - (viewportTop + this._elementHeight) / this._cachedScrollTargetHeight;
+          this._runEffects(this._progress, scrollTop);
+        }
+      },
+
+      /**
+       * Returns true if this app-box is on the screen.
+       * That is, visible in the current viewport.
+       *
+       * @method isOnScreen
+       * @return {boolean}
+       */
+      isOnScreen: function() {
+        return this._elementTop < this._scrollTop + this._cachedScrollTargetHeight
+            && this._elementTop + this._elementHeight > this._scrollTop;
+      },
+
+      _resizeHandler: function() {
+        this.resetLayout();
+      },
+
+      /**
+       * Returns an object containing the progress value of the scroll effects.
+       *
+       * @method getScrollState
+       * @return {Object}
+       */
+      getScrollState: function() {
+        return { progress: this._progress };
+      }
+    });