Gallery: Store image caches in Gallery items.

ui/file_manager/gallery/js/gallery.js

 // Copyright 2014 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.
 
 'use strict';
 
 /**
  * Called from the main frame when unloading.
  * @param {boolean=} opt_exiting True if the app is exiting.
  */
@@ skipping 10 matching lines @@
  * Data model for gallery.
  *
  * @constructor
  * @extends {cr.ui.ArrayDataModel}
  */
 function GalleryDataModel() {
   cr.ui.ArrayDataModel.call(this, []);
   this.metadataCache_ = null;
 }
 
+/**
+ * Maximum number of full size image cache.
+ * @type {number}
+ * @const
+ * @private
+ */
+GalleryDataModel.MAX_FULL_IMAGE_CACHE_ = 3;
+
+/**
+ * Maximum number of screen size image cache.
+ * @type {number}
+ * @const
+ * @private
+ */
+GalleryDataModel.MAX_SCREEN_IMAGE_CACHE_ = 5;
+
 GalleryDataModel.prototype = {
   __proto__: cr.ui.ArrayDataModel.prototype
 };
 
 /**
  * Initializes the data model.
  *
  * @param {MetadataCache} metadataCache Metadata cache.
  * @param {Array.<FileEntry>} entries Image entries.
  * @return {Promise} Promise to be fulfilled with after initialization.
@@ skipping 86 matching lines @@
             // correctly.
             this.splice(this.indexOf(item) + 1, 0, anotherItem);
           }
 
           fulfill();
         }.bind(this));
   }.bind(this));
 };
 
 /**
+ * Evicts image caches in the items.
+ * @param {Gallery.Item} currentSelectedItem Current selected item.
+ */
+GalleryDataModel.prototype.evictCache = function(currentSelectedItem) {
+  // Updates the last accessed date.
+  if (currentSelectedItem)
+    currentSelectedItem.lastAccessed = Date.now();

[mtomasz, 2014/07/28 07:51:21]

I think updating lastAccessed time shouldn't be responsibility of evictCache(),
which should just evict cache.

How about adding a getter and setter for contentImage and screenImage, and
updating accessedTime there + calling evictCache in the setter? WDYT?

[hirono, 2014/07/28 09:10:33]

How about adding touch method and calling it when the selection is changed?
Getters should work. But It may change the priority of cache unintentionally. I
would rather make it controllable a bit more.

[mtomasz, 2014/07/28 09:14:00]

SGTM!

[hirono, 2014/07/28 09:27:21]

Thanks! Done.

+
+  // Sort the item by the last accessed date.
+  var sorted = this.slice().sort(function(a, b) {
+    return b.lastAccessed - a.lastAccessed;
+  });
+
+  // Evict caches.
+  var contentCacheCount = 0;
+  var screenCacheCount = 0;
+  for (var i = 0; i < sorted.length; i++) {
+    if (sorted[i].contentImage) {
+      if (++contentCacheCount > GalleryDataModel.MAX_FULL_IMAGE_CACHE_) {
+        if (sorted[i].contentImage.parentNode) {
+          console.error('The content image has a parent node.');
+        } else {
+          // Force to free the buffer of the canvas by assinng zero size.
+          sorted[i].contentImage.width = 0;
+          sorted[i].contentImage.height = 0;
+          sorted[i].contentImage = null;
+        }
+      }
+    }
+    if (sorted[i].screenImage) {
+      if (++screenCacheCount > GalleryDataModel.MAX_SCREEN_IMAGE_CACHE_) {
+        if (sorted[i].screenImage.parentNode) {
+          console.error('The screen image has a parent node.');
+        } else {
+          // Force to free the buffer of the canvas by assinng zero size.
+          sorted[i].screenImage.width = 0;
+          sorted[i].screenImage.height = 0;
+          sorted[i].screenImage = null;
+        }
+      }
+    }
+  }
+};
+
+/**
  * Gallery for viewing and editing image files.
  *
  * @param {!VolumeManager} volumeManager The VolumeManager instance of the
  *     system.
  * @constructor
  */
 function Gallery(volumeManager) {
   this.context_ = {
     appWindow: chrome.app.window.current(),
     onClose: function() { close(); },
@@ skipping 492 matching lines @@
   return items[0];
 };
 
 /**
   * Selection change event handler.
   * @private
   */
 Gallery.prototype.onSelection_ = function() {
   this.updateSelectionAndState_();
   this.updateShareMenu_();
+  this.dataModel_.evictCache(this.getSelectedItems()[0]);
 };
 
 /**
   * Data model splice event handler.
   * @private
   */
 Gallery.prototype.onSplice_ = function() {
   this.selectionModel_.adjustLength(this.dataModel_.length);
 };
 
@@ skipping 310 matching lines @@
   window.loadTimeData.data = backgroundComponents.stringData;
   gallery = new Gallery(backgroundComponents.volumeManager);
 };
 
 /**
  * Loads entries.
  */
 window.loadEntries = function(entries, selectedEntries) {
   gallery.load(entries, selectedEntries);
 };