Gallery: Store image caches in Gallery items.

ui/file_manager/gallery/js/gallery.js

Index: ui/file_manager/gallery/js/gallery.js
diff --git a/ui/file_manager/gallery/js/gallery.js b/ui/file_manager/gallery/js/gallery.js
index 305def2b307b82b506aefd25ac6e265da851bb06..137e5acf84697045c699be111505c002e944b91f 100644
--- a/ui/file_manager/gallery/js/gallery.js
+++ b/ui/file_manager/gallery/js/gallery.js
@@ -134,6 +134,49 @@ GalleryDataModel.prototype.saveItem = function(item, canvas, overwrite) {
 };
 
 /**
+ * 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();
+
+  // 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 = 2;

[mtomasz, 2014/07/28 05:13:01]

I think the code is too complicated. contentCacheCount becomes a negative number
in #155. What does it mean if count is negative? Can we simplify?

[hirono, 2014/07/28 06:50:32]

Done.

+  var screenCacheCount = 5;
+  for (var i = 0; i < sorted.length; i++) {
+    if (sorted[i].contentImage) {
+      if (contentCacheCount-- <= 0) {
+        if (sorted[i].contentImage.parentNode) {
+          console.error('The content image has a parent node.');
+        } else {
+          sorted[i].contentImage.width = 0;

[mtomasz, 2014/07/28 05:13:01]

Please add a comment, that this is needed to force GC.

[hirono, 2014/07/28 06:50:32]

Done.

+          sorted[i].contentImage.height = 0;
+          sorted[i].contentImage = null;
+        }
+      }
+    }
+    if (sorted[i].screenImage) {
+      if (screenCacheCount-- <= 0) {
+        if (sorted[i].screenImage.parentNode) {
+          console.error('The screen image has a parent node.');
+        } else {
+          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
@@ -646,6 +689,7 @@ Gallery.prototype.getSingleSelectedItem = function() {
 Gallery.prototype.onSelection_ = function() {
   this.updateSelectionAndState_();
   this.updateShareMenu_();
+  this.dataModel_.evictCache(this.getSelectedItems()[0]);
 };
 
 /**