Experimental app list: "All apps" button has a folder-like icon.

ui/app_list/folder_image.cc

+// 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.
+
+#include "ui/app_list/folder_image.h"
+
+#include "ui/app_list/app_list_constants.h"
+#include "ui/app_list/app_list_item.h"
+#include "ui/app_list/app_list_item_list.h"
+#include "ui/app_list/folder_image_source.h"
+#include "ui/app_list/views/contents_view.h"
+#include "ui/base/l10n/l10n_util.h"
+#include "ui/gfx/geometry/rect.h"
+#include "ui/strings/grit/ui_strings.h"
+
+namespace app_list {
+
+FolderImage::FolderImage(AppListItemList* item_list) : item_list_(item_list) {
+  item_list_->AddObserver(this);
+}
+
+FolderImage::~FolderImage() {
+  for (auto* item : top_items_)
+    item->RemoveObserver(this);
+  item_list_->RemoveObserver(this);
+}
+
+void FolderImage::UpdateIcon() {
+  for (auto* item : top_items_)
+    item->RemoveObserver(this);
+  top_items_.clear();
+
+  for (size_t i = 0; i < kNumFolderTopItems && i < item_list_->item_count();
+       ++i) {
+    AppListItem* item = item_list_->item_at(i);
+    item->AddObserver(this);
+    top_items_.push_back(item);
+  }
+  RedrawIconAndNotify();
+}
+
+const gfx::ImageSkia& FolderImage::GetTopIcon(size_t item_index) {
+  CHECK_LT(item_index, top_items_.size());
+  return top_items_[item_index]->icon();
+}
+
+gfx::Rect FolderImage::GetTargetIconRectInFolderForItem(
+    AppListItem* item,
+    const gfx::Rect& folder_icon_bounds) {
+  for (size_t i = 0; i < top_items_.size(); ++i) {
+    if (item->id() == top_items_[i]->id()) {
+      std::vector<gfx::Rect> rects =
+          FolderImageSource::GetTopIconsBounds(folder_icon_bounds);
+      return rects[i];
+    }
+  }
+
+  gfx::Rect target_rect(folder_icon_bounds);
+  target_rect.ClampToCenteredSize(FolderImageSource::ItemIconSize());
+  return target_rect;
+}
+
+void FolderImage::AddObserver(FolderImageObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void FolderImage::RemoveObserver(FolderImageObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+void FolderImage::ItemIconChanged() {
+  // Note: Must update the image only (cannot simply call UpdateIcon), because
+  // UpdateIcon removes and re-adds the FolderImage as an observer of the
+  // AppListItems, which causes the current iterator to call ItemIconChanged
+  // again, and goes into an infinite loop.
+  RedrawIconAndNotify();
+}
+
+void FolderImage::OnListItemAdded(size_t index, AppListItem* item) {
+  if (index < kNumFolderTopItems)
+    UpdateIcon();
+}
+
+void FolderImage::OnListItemRemoved(size_t index, AppListItem* item) {
+  if (index < kNumFolderTopItems)
+    UpdateIcon();
+}
+
+void FolderImage::OnListItemMoved(size_t from_index,
+                                  size_t to_index,
+                                  AppListItem* item) {
+  if (from_index < kNumFolderTopItems || to_index < kNumFolderTopItems)
+    UpdateIcon();
+}
+
+void FolderImage::RedrawIconAndNotify() {
+  FolderImageSource::Icons top_icons;
+  for (const auto* item : top_items_)
+    top_icons.push_back(item->icon());
+
+  const gfx::Size icon_size = gfx::Size(kGridIconDimension, kGridIconDimension);
+  icon_ =
+      gfx::ImageSkia(new FolderImageSource(top_icons, icon_size), icon_size);
+
+  FOR_EACH_OBSERVER(FolderImageObserver, observers_, OnFolderImageUpdated());
+}
+
+}  // namespace app_list