Create implementation of the side panel using a dialog.

ui/webui/resources/cr_elements/cr_drawer/cr_drawer.js

+// Copyright 2016 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.
+
+Polymer({
+  is: 'cr-drawer',
+
+  properties: {
+    /** The opened state of the drawer. */
+    opened: {
+      type: Boolean,
+      value: false,
+      notify: true,
+      reflectToAttribute: true,
+      observer: 'toggleOpen_',
+    },
+
+    /**
+     * The alignment of the drawer on the screen ('left', 'right', 'start' or
+     * 'end'). 'start' computes to left and 'end' to right in LTR layout and
+     * vice versa in RTL layout.
+     */
+    align: {
+      type: String,
+      value: 'left'
+    },
+
+    /**
+     * The computed, read-only position of the drawer on the screen ('left' or
+     * 'right').
+     */
+    position: {
+      type: String,
+      readOnly: true,
+      value: 'left',
+      reflectToAttribute: true
+    },
+  },
+
+  observers: [
+    'resetLayout(position)',
+    'resetPosition_(align, isAttached)',
+  ],
+
+  listeners: {
+    'track': 'track_',
+    'close': 'close',
+  },
+
+  translateOffset_: 0,

[dpapad, 2016/11/07 20:13:24]

Can you document this member var? Both its type but also a short comment about
what info it holds. Same for trackDetails_ and drawerState_.

[hcarmona, 2016/11/16 17:44:54]

Done.

+
+  trackDetails_: null,
+
+  drawerState_: 0,
+
+  boundEscKeydownHandler_: null,
+
+  ready: function() {
+    // Set the scroll direction so you can vertically scroll inside the drawer.
+    this.setScrollDirection('y');
+
+    // Only transition the drawer after its first render (e.g. app-drawer-layout
+    // may need to set the initial opened state which should not be
+    // transitioned).
+    this.setTransitionDuration_('0s');
+  },
+
+  attached: function() {
+    // Only transition the drawer after its first render (e.g. app-drawer-layout
+    // may need to set the initial opened state which should not be
+    // transitioned).
+    Polymer.RenderStatus.afterNextRender(this, function() {
+      this.setTransitionDuration_('');
+      this.boundEscKeydownHandler_ = this.escKeydownHandler_.bind(this);
+      this.resetDrawerState_();
+
+      this.addEventListener('transitionend', this.transitioned_.bind(this));
+    });
+  },
+
+  detached: function() {
+    document.removeEventListener('keydown', this.boundEscKeydownHandler_);
+  },
+
+  /** Opens the drawer. */
+  open: function() {
+    this.opened = true;
+  },
+
+  /** Closes the drawer. */
+  close: function() {
+    this.opened = false;
+  },
+
+  /** Toggles the drawer open and close. */
+  toggle: function() {
+    this.opened = !this.opened;
+  },
+
+  /**
+   * Gets the width of the drawer.
+   * @return {number} The width of the drawer in pixels.
+   */
+  getWidth: function() {
+    return this.$.contentContainer.offsetWidth;
+  },
+
+  /**
+   * Resets the layout. If you changed the size of app-header via CSS
+   * you can notify the changes by either firing the `iron-resize` event
+   * or calling `resetLayout` directly.
+   * @method resetLayout
+   */
+  resetLayout: function() {
+    this.debounce('resetLayout_', function() {
+      this.fire('app-drawer-reset-layout');
+    }, 1);
+  },
+
+  onDialogTap_: function(event) {
+    var rect = this.$.contentContainer.getBoundingClientRect();
+
+    // We can ignore checking top/bottom because dialog is height 100%.
+    if (event.detail.x < rect.left || event.detail.x > rect.right)
+      this.close();
+  },
+
+  /**
+   * Opens and closes the dialog based on the open status.
+   * @param {boolean} open
+   */
+  toggleOpen_: function(open) {
+    if (open && !this.$.contentContainer.open)
+      this.$.contentContainer.showModal();
+    else if (!open && this.$.contentContainer.open)
+      this.$.contentContainer.close();
+  },
+
+  isRTL_: function() {
+    return window.getComputedStyle(this).direction === 'rtl';
+  },
+
+  resetPosition_: function() {
+    switch (this.align) {
+      case 'start':
+        this._setPosition(this.isRTL_() ? 'right' : 'left');
+        return;
+      case 'end':
+        this._setPosition(this.isRTL_() ? 'left' : 'right');
+        return;
+    }
+    this._setPosition(this.align);
+  },
+
+  escKeydownHandler_: function(event) {
+    var ESC_KEYCODE = 27;
+    if (event.keyCode === ESC_KEYCODE) {
+      event.preventDefault();
+      this.close();
+    }
+  },
+
+  track_: function(event) {
+    event.preventDefault();
+
+    switch (event.detail.state) {
+      case 'start':
+        this.trackStart_(event);
+        break;
+      case 'track':
+        this.trackMove_(event);
+        break;
+      case 'end':
+        this.trackEnd_(event);
+        break;
+    }
+  },
+
+  trackStart_: function(event) {
+    this.toggleOpen_(true);  // Always show the dialog when tracking.
+    this.drawerState_ = this.DRAWER_STATE.TRACKING;
+
+    // Disable transitions since style attributes will reflect user tracking.
+    this.setTransitionDuration_('0s');
+    this.style.visibility = 'visible';
+
+    var rect = this.$.contentContainer.getBoundingClientRect();
+    if (this.position === 'left')
+      this.translateOffset_ = rect.left;
+    else
+      this.translateOffset_ = rect.right - window.innerWidth;
+
+    this.trackDetails_ = [];
+  },
+
+  trackMove_: function(event) {
+    this.translateDrawer_(event.detail.dx + this.translateOffset_);
+
+    // Use Date.now() since event.timeStamp is inconsistent across browsers
+    // (e.g. most browsers use milliseconds but FF 44 uses microseconds).
+    this.trackDetails_.push({
+      dx: event.detail.dx,
+      timeStamp: Date.now()
+    });
+  },
+
+  trackEnd_: function(event) {
+    var x = event.detail.dx + this.translateOffset_;
+    var drawerWidth = this.getWidth();
+    var isPositionLeft = this.position === 'left';
+    var isInEndState = isPositionLeft ? (x >= 0 || x <= -drawerWidth) :
+      (x <= 0 || x >= drawerWidth);
+
+    if (!isInEndState) {
+      // No longer need the track events after this method returns - allow them
+      // to be cleaned up.
+      var trackDetails = this.trackDetails_;
+      this.trackDetails_ = null;
+
+      this.filngDrawer_(event, trackDetails);
+      if (this.drawerState_ === this.DRAWER_STATE.FLINGING)
+        return;
+    }
+
+    // If the drawer is not flinging, toggle the opened state based on the
+    // position of the drawer.
+    var halfWidth = drawerWidth / 2;
+    if (event.detail.dx < -halfWidth)
+      this.opened = this.position === 'right';
+    else if (event.detail.dx > halfWidth)
+      this.opened = this.position === 'left';
+
+    // The dialog open state can go out of sync with the |opened| property.
+    this.toggleOpen_(this.opened);
+
+    if (isInEndState)
+      this.resetDrawerState_();
+
+    this.setTransitionDuration_('');
+    this.resetDrawerTranslate_();
+    this.style.visibility = '';
+  },
+
+  calculateVelocity_: function(event, trackDetails) {
+    // Find the oldest track event that is within 100ms using binary search.
+    var now = Date.now();
+    var timeLowerBound = now - 100;
+    var trackDetail;
+    var min = 0;
+    var max = trackDetails.length - 1;
+
+    while (min <= max) {
+      // Floor of average of min and max.
+      var mid = (min + max) >> 1;
+      var d = trackDetails[mid];
+      if (d.timeStamp >= timeLowerBound) {
+        trackDetail = d;
+        max = mid - 1;
+      } else {
+        min = mid + 1;
+      }
+    }
+
+    if (trackDetail) {
+      var dx = event.detail.dx - trackDetail.dx;
+      var dt = (now - trackDetail.timeStamp) || 1;
+      return dx / dt;
+    }
+    return 0;
+  },
+
+  filngDrawer_: function(event, trackDetails) {
+    var velocity = this.calculateVelocity_(event, trackDetails);
+
+    // Do not fling if velocity is not above a threshold.
+    if (Math.abs(velocity) < this.MIN_FLING_THRESHOLD) {
+      return;
+    }
+
+    this.drawerState_ = this.DRAWER_STATE.FLINGING;
+
+    var x = event.detail.dx + this.translateOffset_;
+    var drawerWidth = this.getWidth();
+    var isPositionLeft = this.position === 'left';
+    var isVelocityPositive = velocity > 0;
+    var isClosingLeft = !isVelocityPositive && isPositionLeft;
+    var isClosingRight = isVelocityPositive && !isPositionLeft;
+    var dx;
+
+    if (isClosingLeft)
+      dx = -(x + drawerWidth);
+    else if (isClosingRight)
+      dx = (drawerWidth - x);
+    else
+      dx = -x;
+
+    // Enforce a minimum transition velocity to make the drawer feel snappy.
+    if (isVelocityPositive) {
+      velocity = Math.max(velocity, this.MIN_TRANSITION_VELOCITY);
+      this.opened = this.position === 'left';
+    } else {
+      velocity = Math.min(velocity, -this.MIN_TRANSITION_VELOCITY);
+      this.opened = this.position === 'right';
+    }
+
+    // The dialog open state can go out of sync with the |opened| property.
+    this.toggleOpen_(this.opened);
+
+    // Calculate the amount of time needed to finish the transition based on the
+    // initial slope of the timing function.
+    this.setTransitionDuration_((this.FLING_INITIAL_SLOPE * dx / velocity)
+        + 'ms');
+    this.setTransiitonTimingFunction_(this.FLING_TIMING_FUNCTION);
+
+    this.resetDrawerTranslate_();
+  },
+
+  transitioned_: function(event) {
+    // contentContainer will transition on opened state changed, and scrim will
+    // transition on persistent state changed when opened - these are the
+    // transitions we are interested in.
+    var target = Polymer.dom(event).rootTarget;
+    if (target === this.$.contentContainer || target === this.$.scrim) {
+
+      // If the drawer was flinging, we need to reset the style attributes.
+      if (this.drawerState_ === this.DRAWER_STATE.FLINGING) {
+        this.setTransitionDuration_('');
+        this.setTransiitonTimingFunction_('');
+        this.style.visibility = '';
+      }
+
+      this.resetDrawerState_();
+    }
+  },
+
+  setTransitionDuration_: function(duration) {

[dpapad, 2016/11/07 20:13:24]

Let's annotate all methods in this class with @param, @private, @return where
applicable.

[hcarmona, 2016/11/16 17:44:54]

Done.

+    this.$.contentContainer.style.transitionDuration = duration;
+    this.$.scrim.style.transitionDuration = duration;
+  },
+
+  setTransiitonTimingFunction_: function(timingFunction) {
+    this.$.contentContainer.style.transitionTimingFunction = timingFunction;
+    this.$.scrim.style.transitionTimingFunction = timingFunction;
+  },
+
+  translateDrawer_: function(x) {
+    var drawerWidth = this.getWidth();
+
+    if (this.position === 'left') {
+      x = Math.max(-drawerWidth, Math.min(x, 0));
+      this.$.scrim.style.opacity = 1 + x / drawerWidth;
+    } else {
+      x = Math.max(0, Math.min(x, drawerWidth));
+      this.$.scrim.style.opacity = 1 - x / drawerWidth;
+    }
+
+    this.translate3d(x + 'px', '0', '0', this.$.contentContainer);
+  },
+
+  resetDrawerTranslate_: function() {
+    this.$.scrim.style.opacity = '';
+    this.transform('', this.$.contentContainer);
+  },
+
+  resetDrawerState_: function() {
+    var oldState = this.drawerState_;
+    this.drawerState_ = this.opened ?  this.DRAWER_STATE.OPENED :
+        this.DRAWER_STATE.CLOSED;
+
+    if (oldState !== this.drawerState_) {
+      if (this.drawerState_ === this.DRAWER_STATE.OPENED) {
+        document.addEventListener('keydown', this.boundEscKeydownHandler_);
+        document.body.style.overflow = 'hidden';
+      } else {
+        document.removeEventListener('keydown', this.boundEscKeydownHandler_);
+        document.body.style.overflow = '';
+      }
+
+      // Don't fire the event on initial load.
+      if (oldState !== this.DRAWER_STATE.INIT)
+        this.fire('app-drawer-transitioned');
+    }
+  },
+
+  MIN_FLING_THRESHOLD: 0.2,
+
+  MIN_TRANSITION_VELOCITY: 1.2,
+
+  FLING_TIMING_FUNCTION: 'cubic-bezier(0.667, 1, 0.667, 1)',
+
+  FLING_INITIAL_SLOPE: 1.5,
+
+  DRAWER_STATE: {
+    INIT: 0,
+    OPENED: 1,
+    OPENED_PERSISTENT: 2,
+    CLOSED: 3,
+    TRACKING: 4,
+    FLINGING: 5
+  }
+});