Make painting app list items more efficient by caching the labels.

ui/app_list/views/app_list_item_view.cc

 // Copyright (c) 2012 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/views/app_list_item_view.h"
 
 #include <algorithm>
 
 #include "base/utf_string_conversions.h"
 #include "grit/ui_resources.h"
 #include "ui/app_list/app_list_item_model.h"
 #include "ui/app_list/views/apps_grid_view.h"
+#include "ui/app_list/views/cached_label.h"
 #include "ui/base/accessibility/accessible_view_state.h"
 #include "ui/base/animation/throb_animation.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/compositor/layer.h"
 #include "ui/compositor/scoped_layer_animation_settings.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/font.h"
 #include "ui/gfx/image/image_skia_operations.h"
 #include "ui/gfx/transform_util.h"
 #include "ui/views/controls/image_view.h"
@@ skipping 35 matching lines @@
 
 // static
 const char AppListItemView::kViewClassName[] = "ui/app_list/AppListItemView";
 
 AppListItemView::AppListItemView(AppsGridView* apps_grid_view,
                                  AppListItemModel* model)
     : CustomButton(apps_grid_view),
       model_(model),
       apps_grid_view_(apps_grid_view),
       icon_(new views::ImageView),
-      title_(new views::Label),
+      title_(new CachedLabel),
       ui_state_(UI_STATE_NORMAL),
       touch_dragging_(false) {
   icon_->set_interactive(false);
 
   ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
   title_->SetBackgroundColor(0);
   title_->SetAutoColorReadabilityEnabled(false);
   title_->SetEnabledColor(kTitleColor);
   title_->SetFont(rb.GetFont(ui::ResourceBundle::SmallBoldFont));
   title_->SetHorizontalAlignment(gfx::ALIGN_LEFT);
   title_->SetVisible(!model_->is_installing());
+  title_->Invalidate();

[benwells, 2013/03/12 04:58:11]

nit: is this needed? CachedLabel initializes needs_repaint_ to true.

[koz (OOO until 15th September), 2013/03/13 00:30:36]

Not needed, but needs_repaint_ could just as easily initialise to false. I also
think this adds clarity.

 
   const gfx::ShadowValue kIconShadows[] = {
     gfx::ShadowValue(gfx::Point(0, 2), 2, SkColorSetARGB(0x24, 0, 0, 0)),
   };
   icon_shadows_.assign(kIconShadows, kIconShadows + arraysize(kIconShadows));
 
   AddChildView(icon_);
   AddChildView(title_);
 
   ItemIconChanged();
@@ skipping 79 matching lines @@
   DCHECK(apps_grid_view_->IsDraggedView(this));
   SetUIState(UI_STATE_DRAGGING);
 }
 
 void AppListItemView::ItemIconChanged() {
   UpdateIcon();
 }
 
 void AppListItemView::ItemTitleChanged() {
   title_->SetText(UTF8ToUTF16(model_->title()));
+  title_->Invalidate();
 }
 
 void AppListItemView::ItemHighlightedChanged() {
   apps_grid_view_->EnsureViewVisible(this);
   SchedulePaint();
 }
 
 void AppListItemView::ItemIsInstallingChanged() {
   if (model_->is_installing())
     apps_grid_view_->EnsureViewVisible(this);
@@ skipping 100 matching lines @@
 
 void AppListItemView::StateChanged() {
   if (state() == STATE_HOVERED || state() == STATE_PRESSED) {
     apps_grid_view_->SetSelectedView(this);
     title_->SetEnabledColor(kTitleHoverColor);
   } else {
     apps_grid_view_->ClearSelectedView(this);
     model_->SetHighlighted(false);
     title_->SetEnabledColor(kTitleColor);
   }
+  title_->Invalidate();
 }
 
 bool AppListItemView::ShouldEnterPushedState(const ui::Event& event) {
   // Don't enter pushed state for ET_GESTURE_TAP_DOWN so that hover gray
   // background does not show up during scroll.
   if (event.type() == ui::ET_GESTURE_TAP_DOWN)
     return false;
 
   return views::CustomButton::ShouldEnterPushedState(event);
 }
@@ skipping 86 matching lines @@
         SetTouchDragging(false);
       break;
     default:
       break;
   }
   if (!event->handled())
     CustomButton::OnGestureEvent(event);
 }
 
 }  // namespace app_list