Move settings-section animations into setting-section, make better

chrome/browser/resources/settings/settings_page/settings_section.js

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview
  * 'settings-section' shows a paper material themed section with a header
  * which shows its page title.
+

[dschuyler, 2016/08/04 18:36:51]

Maybe remove blank line or add an '*'?

+ * The section can expand vertically to to its container's padding edge.
  *
  * Example:
  *
  *    <settings-section page-title="[[pageTitle]]" section="privacy">
  *      <!-- Insert your section controls here -->
  *    </settings-section>
  */
 Polymer({
   is: 'settings-section',
 
   properties: {
     /**
      * The current active route.
      */
     currentRoute: Object,
 
     /**
-     * The section is expanded to a full-page view when this property matches
+     * The section name should match a name specified in route.js. The
+     * MainPageBehavior will expand this section if this section name matches
      * currentRoute.section.
-     *
-     * The section name must match the name specified in settings_router.js.
      */
-    section: {
-      type: String,
-    },
+    section: String,
+
+    /** Title for the section header. */
+    pageTitle: String,
 
     /**
-     * Title for the page header and navigation menu.
+     * Original height of the collapsed section, used as the target height when
+     * collapsing after being expanded.
+     * TODO(michaelpg): Get the height dynamically when collapsing using the
+     * card's main page.
+     * @private
      */
-    pageTitle: String,
+    collapsedHeight_: {
+      type: Number,
+      value: NaN,
+    },
+  },
+
+  /**
+   * @return {boolean} True if the section is currently rendered and not
+   * already expanded or transitioning.
+   */
+  canAnimateExpand: function() {
+    return !this.classList.contains('expanding') &&
+        !this.classList.contains('expanded') && this.$.card.clientHeight > 0;
+  },
+
+  /**
+   * Animates the section expanding to fill the container. The section is fixed
+   * in the viewport during the animation, making it safe to adjust the rest of
+   * the DOM after calling this. The section adds the 'expanding' class while
+   * the animation plays and 'expanded' after it finishes.
+   *
+   * The animation does not "last", so the parent must properly position it
+   * afterwards in its container.
+   *
+   * @param {!HTMLElement} container The scrolling container to fill.
+   * @return {!settings.animation.Animation}
+   */
+  animateExpand: function(container) {
+    // Set the section's height so its card can be removed from the flow
+    // without affecting the surrounding sections during the animation.
+    this.collapsedHeight_ = this.clientHeight;
+    this.style.height = this.collapsedHeight_ + 'px';
+
+    this.classList.add('expanding');
+
+    // Start the card in place, at its distance from the container's padding.
+    var startTop = this.$.card.getBoundingClientRect().top + 'px';
+    var startHeight = this.$.card.clientHeight + 'px';
+
+    // Target position is the container's top edge in the viewport.
+    var containerTop = container.getBoundingClientRect().top;
+    var endTop = containerTop + 'px';
+    // The card should stretch from the bottom of the toolbar to the bottom of
+    // the page. calc(100% - top) lets the card resize if the window resizes.
+    var endHeight = 'calc(100% - ' + containerTop + 'px)';
+
+    var animation =
+        this.animateCard_('fixed', startTop, endTop, startHeight, endHeight);
+
+    // Whether the animation fails or succeeds, clean up the properties we set.
+    animation.finished.catch(function() {}).then(function() {
+      this.classList.remove('expanding');
+      this.style.height = '';
+    }.bind(this));
+    return animation;
+  },
+
+  /** @return {boolean} True if the section is currently expanded. */
+  canAnimateCollapse: function() {
+    return this.classList.contains('expanded') && this.clientHeight > 0 &&
+        !Number.isNaN(this.collapsedHeight_);
+  },
+
+  /**
+   * Prepares for the animation before the other sections become visible.
+   * Call before animateCollapse().
+   */
+  setUpAnimateCollapse: function(container) {
+    // Prepare the dimensions and set position: fixed.
+    this.$.card.style.width = this.$.card.clientWidth + 'px';
+    this.$.card.style.height = this.$.card.clientHeight + 'px';
+    this.$.card.style.top = container.getBoundingClientRect().top + 'px';
+    this.$.card.style.position = 'fixed';
+
+    // The section can now collapse back into its original height the page so
+    // the other sections appear in the right places.
+    this.classList.add('collapsing');
+    this.style.height = this.collapsedHeight_ + 'px';
+  },
+
+  /**
+   * Collapses an expanded section's card back into position in the main page.
+   * Call after calling animateCollapse(), unhiding other content and scrolling.
+   * @param {!HTMLElement} container The scrolling container the card fills.
+   * @return {!settings.animation.Animation}
+   */
+  animateCollapse: function(container) {
+    // Make the card position: absolute, so scrolling is less of a crapshoot.
+    // First find the current distance between this section and the card using
+    // fixed coordinates; the absolute distance will be the same.
+    var fixedCardTop = this.$.card.getBoundingClientRect().top;
+    var fixedSectionTop = this.getBoundingClientRect().top;
+    var distance = fixedCardTop - fixedSectionTop;
+
+    // The target position is right below our header.
+    var headerStyle = getComputedStyle(this.$.header);
+    var cardTargetTop = this.$.header.offsetHeight +
+        parseFloat(headerStyle.marginBottom) +
+        parseFloat(headerStyle.marginTop);
+
+    // Start the card at its current height and distance from our top.
+    var startTop = distance + 'px';
+    var startHeight = this.$.card.style.height;
+
+    // End at the bottom of our header.
+    var endTop = cardTargetTop + 'px';
+    var endHeight = (this.collapsedHeight_ - cardTargetTop) + 'px';
+
+    // The card no longer needs position: fixed.
+    this.$.card.style.position = '';
+
+    // Collapse this section, animate the card into place, and remove its
+    // other properties.
+    var animation =
+        this.animateCard_('absolute', startTop, endTop, startHeight, endHeight);
+    this.$.card.style.width = '';
+    this.$.card.style.height = '';
+    this.$.card.style.top = '';
+
+    // Whether the animation fails or succeeds, clean up the properties we set.
+    animation.finished.catch(function() {}).then(function() {
+      // The card now determines the section's height automatically.
+      this.style.height = '';
+      this.classList.remove('collapsing');
+    }.bind(this));
+    return animation;
+  },
+
+  /**
+   * Helper function to animate the card's position and height.
+   * @param {string} position CSS position property.
+   * @param {string} startTop Initial top value.
+   * @param {string} endTop Target top value.
+   * @param {string} startHeight Initial height value.
+   * @param {string} endHeight Target height value.
+   * @return {!settings.animation.Animation}
+   * @private
+   */
+  animateCard_: function(position, startTop, endTop, startHeight, endHeight) {
+    // Width does not change.
+    var width = this.$.card.clientWidth + 'px';
+
+    var startFrame = {
+      position: position,
+      width: width,
+      top: startTop,
+      height: startHeight,
+    };
+
+    var endFrame = {
+      position: position,
+      width: width,
+      top: endTop,
+      height: endHeight,
+    };
+
+    var options = /** @type {!KeyframeEffectOptions} */({
+      duration: settings.animation.Timing.DURATION,
+      easing: settings.animation.Timing.EASING,
+    });
+
+    return new settings.animation.Animation(
+        this.$.card, [startFrame, endFrame], options);
   },
 });