Optimizing the time taken to build and show the WrenchMenu.

chrome/browser/ui/views/toolbar/wrench_menu.cc

 // Copyright 2013 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 "chrome/browser/ui/views/toolbar/wrench_menu.h"
 
 #include <algorithm>
 #include <cmath>
 #include <set>
 
@@ skipping 353 matching lines @@
 
   // Overridden from WrenchMenuObserver:
   void WrenchMenuDestroyed() override {
     menu_->RemoveObserver(this);
     menu_ = NULL;
     menu_model_ = NULL;
   }
 
  protected:
   WrenchMenu* menu() { return menu_; }
+  const WrenchMenu* menu() const { return menu_; }
   ButtonMenuItemModel* menu_model() { return menu_model_; }
 
  private:
   // Hosting WrenchMenu.
   // WARNING: this may be NULL during shutdown.
   WrenchMenu* menu_;
 
   // The menu model containing the increment/decrement/reset items.
   // WARNING: this may be NULL during shutdown.
   ButtonMenuItemModel* menu_model_;
@@ skipping 101 matching lines @@
            ButtonMenuItemModel* menu_model,
            int decrement_index,
            int increment_index,
            int fullscreen_index)
       : WrenchMenuView(menu, menu_model),
         fullscreen_index_(fullscreen_index),
         increment_button_(NULL),
         zoom_label_(NULL),
         decrement_button_(NULL),
         fullscreen_button_(NULL),
-        zoom_label_width_(0) {
+        zoom_label_max_width_(0),
+        zoom_label_max_width_valid_(false) {
     browser_zoom_subscription_ =
         ui_zoom::ZoomEventManager::GetForBrowserContext(
             menu->browser_->profile())
             ->AddZoomLevelChangedCallback(
                 base::Bind(&WrenchMenu::ZoomView::OnZoomLevelChanged,
                            base::Unretained(this)));
 
     decrement_button_ = CreateButtonWithAccName(
         IDS_ZOOM_MINUS2, InMenuButtonBackground::LEFT_BUTTON,
         decrement_index, IDS_ACCNAME_ZOOM_MINUS2);
 
     zoom_label_ = new Label(
         l10n_util::GetStringFUTF16Int(IDS_ZOOM_PERCENT, 100));
     zoom_label_->SetAutoColorReadabilityEnabled(false);
     zoom_label_->SetHorizontalAlignment(gfx::ALIGN_RIGHT);
 
     InMenuButtonBackground* center_bg =
         new InMenuButtonBackground(InMenuButtonBackground::RIGHT_BUTTON);
     zoom_label_->set_background(center_bg);
 
     AddChildView(zoom_label_);
-    zoom_label_width_ = MaxWidthForZoomLabel();
+    zoom_label_max_width_valid_ = false;
 
     increment_button_ = CreateButtonWithAccName(
         IDS_ZOOM_PLUS2, InMenuButtonBackground::RIGHT_BUTTON,
         increment_index, IDS_ACCNAME_ZOOM_PLUS2);
 
     center_bg->SetOtherButtons(decrement_button_, increment_button_);
 
     fullscreen_button_ = new FullscreenButton(this);
     // all buttons on menu should must be a custom button in order for
     // the keyboard nativigation work.
@@ skipping 25 matching lines @@
   // Overridden from View.
   gfx::Size GetPreferredSize() const override {
     // The increment/decrement button are forced to the same width.
     int button_width = std::max(increment_button_->GetPreferredSize().width(),
                                 decrement_button_->GetPreferredSize().width());
     int fullscreen_width =
         fullscreen_button_->GetPreferredSize().width() + kFullscreenPadding;
     // Returned height doesn't matter as MenuItemView forces everything to the
     // height of the menuitemview. Note that we have overridden the height when
     // constructing the menu.
-    return gfx::Size(button_width + zoom_label_width_ + button_width +
-                     fullscreen_width, 0);
+    return gfx::Size(
+        button_width + ZoomLabelMaxWidth() + button_width + fullscreen_width,
+        0);
   }
 
   void Layout() override {
     int x = 0;
     int button_width = std::max(increment_button_->GetPreferredSize().width(),
                                 decrement_button_->GetPreferredSize().width());
     gfx::Rect bounds(0, 0, button_width, height());
 
     decrement_button_->SetBoundsRect(bounds);
 
     x += bounds.width();
     bounds.set_x(x);
-    bounds.set_width(zoom_label_width_);
+    bounds.set_width(ZoomLabelMaxWidth());
     zoom_label_->SetBoundsRect(bounds);
 
     x += bounds.width();
     bounds.set_x(x);
     bounds.set_width(button_width);
     increment_button_->SetBoundsRect(bounds);
 
     x += bounds.width();
     bounds.set_x(x);
     bounds.set_width(fullscreen_button_->GetPreferredSize().width() +
                      kFullscreenPadding);
     fullscreen_button_->SetBoundsRect(bounds);
   }
 
   void OnNativeThemeChanged(const ui::NativeTheme* theme) override {
     WrenchMenuView::OnNativeThemeChanged(theme);
 
     const MenuConfig& menu_config = MenuConfig::instance(theme);
     zoom_label_->SetBorder(views::Border::CreateEmptyBorder(
         0, kZoomLabelHorizontalPadding, 0, kZoomLabelHorizontalPadding));
     zoom_label_->SetFontList(menu_config.font_list);
-    zoom_label_width_ = MaxWidthForZoomLabel();
+    zoom_label_max_width_valid_ = false;
 
     if (theme) {
       zoom_label_->SetEnabledColor(theme->GetSystemColor(
           ui::NativeTheme::kColorId_EnabledMenuItemForegroundColor));
       gfx::ImageSkia* full_screen_image =
           ui::ResourceBundle::GetSharedInstance().GetImageSkiaNamed(
               IDR_FULLSCREEN_MENU_BUTTON);
       SkColor fg_color = theme->GetSystemColor(
           ui::NativeTheme::kColorId_SelectedMenuItemForegroundColor);
       gfx::ImageSkia hovered_fullscreen_image(
@@ skipping 34 matching lines @@
       if (zoom_controller)
         zoom = zoom_controller->GetZoomPercent();
       increment_button_->SetEnabled(zoom <
                                     selected_tab->GetMaximumZoomPercent());
       decrement_button_->SetEnabled(zoom >
                                     selected_tab->GetMinimumZoomPercent());
     }
     zoom_label_->SetText(
         l10n_util::GetStringFUTF16Int(IDS_ZOOM_PERCENT, zoom));
 
-    zoom_label_width_ = MaxWidthForZoomLabel();
+    zoom_label_max_width_valid_ = false;
   }
 
-  // Calculates the max width the zoom string can be.
-  int MaxWidthForZoomLabel() {
-    const gfx::FontList& font_list = zoom_label_->font_list();
-    int border_width =
-        zoom_label_->border() ? zoom_label_->border()->GetInsets().width() : 0;
+  // Returns the max width the zoom string can be.
+  int ZoomLabelMaxWidth() const {
+    if (!zoom_label_max_width_valid_) {
+      const gfx::FontList& font_list = zoom_label_->font_list();
+      int border_width = zoom_label_->border()
+                             ? zoom_label_->border()->GetInsets().width()
+                             : 0;
 
-    int max_w = 0;
+      int max_w = 0;
 
-    WebContents* selected_tab =
-        menu()->browser_->tab_strip_model()->GetActiveWebContents();
-    if (selected_tab) {
-      int min_percent = selected_tab->GetMinimumZoomPercent();
-      int max_percent = selected_tab->GetMaximumZoomPercent();
+      WebContents* selected_tab =
+          menu()->browser_->tab_strip_model()->GetActiveWebContents();
+      if (selected_tab) {
+        int min_percent = selected_tab->GetMinimumZoomPercent();
+        int max_percent = selected_tab->GetMaximumZoomPercent();
 
-      int step = (max_percent - min_percent) / 10;
-      for (int i = min_percent; i <= max_percent; i += step) {
-        int w = gfx::GetStringWidth(
-            l10n_util::GetStringFUTF16Int(IDS_ZOOM_PERCENT, i), font_list);
-        max_w = std::max(w, max_w);
+        int step = (max_percent - min_percent) / 10;
+        for (int i = min_percent; i <= max_percent; i += step) {
+          int w = gfx::GetStringWidth(
+              l10n_util::GetStringFUTF16Int(IDS_ZOOM_PERCENT, i), font_list);
+          max_w = std::max(w, max_w);
+        }
+      } else {
+        max_w = gfx::GetStringWidth(
+            l10n_util::GetStringFUTF16Int(IDS_ZOOM_PERCENT, 100), font_list);
       }
-    } else {
-      max_w = gfx::GetStringWidth(
-          l10n_util::GetStringFUTF16Int(IDS_ZOOM_PERCENT, 100), font_list);
+      zoom_label_max_width_ = max_w + border_width;
+
+      zoom_label_max_width_valid_ = true;
     }
-
-    return max_w + border_width;
+    return zoom_label_max_width_;
   }
 
   // Index of the fullscreen menu item in the model.
   const int fullscreen_index_;
 
   scoped_ptr<content::HostZoomMap::Subscription> browser_zoom_subscription_;
   content::NotificationRegistrar registrar_;
 
   // Button for incrementing the zoom.
   LabelButton* increment_button_;
 
   // Label showing zoom as a percent.
   Label* zoom_label_;
 
   // Button for decrementing the zoom.
   LabelButton* decrement_button_;
 
   ImageButton* fullscreen_button_;
 
-  // Width given to |zoom_label_|. This is the width at 100%.
-  int zoom_label_width_;
+  // Cached width of how wide the zoom label string can be. This is the width at
+  // 100%. This should not be accessed directly, use ZoomLabelMaxWidth()
+  // instead. This value is cached because is depends on multiple calls to
+  // gfx::GetStringWidth(...) which are expensive.
+  mutable int zoom_label_max_width_;
+
+  // Flag tracking whether calls to ZoomLabelMaxWidth() need to re-calculate
+  // the label width, because the cached value may no longer be correct.
+  mutable bool zoom_label_max_width_valid_;
 
   DISALLOW_COPY_AND_ASSIGN(ZoomView);
 };
 
 // RecentTabsMenuModelDelegate  ------------------------------------------------
 
 // Provides the ui::MenuModelDelegate implementation for RecentTabsSubMenuModel
 // items.
 class WrenchMenu::RecentTabsMenuModelDelegate : public ui::MenuModelDelegate {
  public:
@@ skipping 535 matching lines @@
                                 0,
                                 BookmarkMenuDelegate::SHOW_PERMANENT_FOLDERS,
                                 BOOKMARK_LAUNCH_LOCATION_WRENCH_MENU);
 }
 
 int WrenchMenu::ModelIndexFromCommandId(int command_id) const {
   CommandIDToEntry::const_iterator ix = command_id_to_entry_.find(command_id);
   DCHECK(ix != command_id_to_entry_.end());
   return ix->second.second;
 }