MD Downloads: use <iron-list> to render download items

chrome/browser/resources/md_downloads/manager.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.
 
 cr.define('downloads', function() {
   var Manager = Polymer({
     is: 'downloads-manager',
 
     properties: {
       hasDownloads_: {
         type: Boolean,
         value: false,
       },
+
+      items_: {
+        type: Array,
+      },
     },
 
     /**
-     * @return {number} A guess at how many items could be visible at once.
-     * @private
-     */
-    guesstimateNumberOfVisibleItems_: function() {
-      var toolbarHeight = this.$.toolbar.offsetHeight;
-      return Math.floor((window.innerHeight - toolbarHeight) / 46) + 1;
-    },
-
-    /**
      * @param {Event} e
      * @private
      */
     onCanExecute_: function(e) {
       e = /** @type {cr.ui.CanExecuteEvent} */(e);
       switch (e.command.id) {
         case 'undo-command':
           e.canExecute = this.$.toolbar.canUndo();
           break;
         case 'clear-all-command':
@@ skipping 16 matching lines @@
     /** @private */
     onLoad_: function() {
       cr.ui.decorate('command', cr.ui.Command);
       document.addEventListener('canExecute', this.onCanExecute_.bind(this));
       document.addEventListener('command', this.onCommand_.bind(this));
 
       // Shows all downloads.
       downloads.ActionService.getInstance().search('');
     },
 
-    /** @private */
-    rebuildFocusGrid_: function() {
-      var activeElement = this.shadowRoot.activeElement;
-
-      var activeItem;
-      if (activeElement && activeElement.tagName == 'downloads-item')
-        activeItem = activeElement;
-
-      var activeControl = activeItem && activeItem.shadowRoot.activeElement;
-
-      /** @private {!cr.ui.FocusGrid} */
-      this.focusGrid_ = this.focusGrid_ || new cr.ui.FocusGrid;
-      this.focusGrid_.destroy();
-
-      var boundary = this.$['downloads-list'];
-
-      this.items_.forEach(function(item) {
-        var focusRow = new downloads.FocusRow(item.content, boundary);
-        this.focusGrid_.addRow(focusRow);
-
-        if (item == activeItem && !cr.ui.FocusRow.isFocusable(activeControl))
-          focusRow.getEquivalentElement(activeControl).focus();
-      }, this);
-
-      this.focusGrid_.ensureRowActive();
-    },
-
     /**
      * @return {number} The number of downloads shown on the page.
      * @private
      */
     size_: function() {
       return this.items_.length;
     },
 
     /**
      * Called when all items need to be updated.
      * @param {!Array<!downloads.Data>} list A list of new download data.
      * @private
      */
     updateAll_: function(list) {
-      var oldIdMap = this.idMap_ || {};
-
-      /** @private {!Object<!downloads.Item>} */
-      this.idMap_ = {};
-
-      /** @private {!Array<!downloads.Item>} */
-      this.items_ = [];
-
-      if (!this.iconLoader_) {
-        var guesstimate = Math.max(this.guesstimateNumberOfVisibleItems_(), 1);
-        /** @private {downloads.ThrottledIconLoader} */
-        this.iconLoader_ = new downloads.ThrottledIconLoader(guesstimate);
-      }
+      /** @private {!Object<number>} */
+      this.idToIndex_ = {};
 
       for (var i = 0; i < list.length; ++i) {
         var data = list[i];
-        var id = data.id;
 
-        // Re-use old items when possible (saves work, preserves focus).
-        var item = oldIdMap[id] || new downloads.Item(this.iconLoader_);
+        this.idToIndex_[data.id] = data.index = i;
 
-        this.idMap_[id] = item;  // Associated by ID for fast lookup.
-        this.items_.push(item);  // Add to sorted list for order.
-
-        // Render |item| but don't actually add to the DOM yet. |this.items_|
-        // must be fully created to be able to find the right spot to insert.
-        item.update(data);
-
-        // Collapse redundant dates.
         var prev = list[i - 1];
-        item.hideDate = !!prev && prev.date_string == data.date_string;
-
-        delete oldIdMap[id];
+        data.hideDate = !!prev && prev.date_string == data.date_string;
       }
 
-      // Remove stale, previously rendered items from the DOM.
-      for (var id in oldIdMap) {
-        if (oldIdMap[id].parentNode)
-          oldIdMap[id].parentNode.removeChild(oldIdMap[id]);
-        delete oldIdMap[id];
-      }
-
-      for (var i = 0; i < this.items_.length; ++i) {
-        var item = this.items_[i];
-        if (item.parentNode)  // Already in the DOM; skip.
-          continue;
-
-        var before = null;
-        // Find the next rendered item after this one, and insert before it.
-        for (var j = i + 1; !before && j < this.items_.length; ++j) {
-          if (this.items_[j].parentNode)
-            before = this.items_[j];
-        }
-        // If |before| is null, |item| will just get added at the end.
-        this.$['downloads-list'].insertBefore(item, before);
-      }
+      // TODO(dbeam): this resets the scroll position, which is a huge bummer.
+      // Removing something from the bottom of the list should not scroll you
+      // back to the top. The grand plan is to restructure how the C++ sends the
+      // JS data so that it only gets updates (rather than the most recent set
+      // of items). TL;DR - we can't ship with this bug.
+      this.items_ = list;
 
       var hasDownloads = this.size_() > 0;
       if (!hasDownloads) {
         var isSearching = downloads.ActionService.getInstance().isSearching();
         var messageToShow = isSearching ? 'noSearchResults' : 'noDownloads';
         this.$['no-downloads'].querySelector('span').textContent =
             loadTimeData.getString(messageToShow);
       }
       this.hasDownloads_ = hasDownloads;
 
       if (loadTimeData.getBoolean('allowDeletingHistory'))
         this.$.toolbar.downloadsShowing = this.hasDownloads_;
 
       this.$.panel.classList.remove('loading');
-
-      var allReady = this.items_.map(function(i) { return i.readyPromise; });
-      Promise.all(allReady).then(this.rebuildFocusGrid_.bind(this));
     },
 
     /**
      * @param {!downloads.Data} data
      * @private
      */
     updateItem_: function(data) {
-      var item = this.idMap_[data.id];
-
-      var activeControl = this.shadowRoot.activeElement == item ?
-          item.shadowRoot.activeElement : null;
-
-      item.update(data);
-
-      this.async(function() {
-        if (activeControl && !cr.ui.FocusRow.isFocusable(activeControl)) {
-          var focusRow = this.focusGrid_.getRowForRoot(item.content);
-          focusRow.getEquivalentElement(activeControl).focus();
-        }
-      }.bind(this));
+      var index = this.idToIndex_[data.id];
+      this.set('items_.' + index, data);
+      this.$['downloads-list'].updateSizeForItem(index);
     },
   });
 
   Manager.size = function() {
     return document.querySelector('downloads-manager').size_();
   };
 
   Manager.updateAll = function(list) {
     document.querySelector('downloads-manager').updateAll_(list);
   };
 
   Manager.updateItem = function(item) {
     document.querySelector('downloads-manager').updateItem_(item);
   };
 
   Manager.onLoad = function() {
     document.querySelector('downloads-manager').onLoad_();
   };
 
   return {Manager: Manager};
 });
 
 window.addEventListener('load', downloads.Manager.onLoad);