Make the bookmark toolbar folders act like a menu bar....

chrome/browser/gtk/menu_bar_helper.h

+// Copyright (c) 2009 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.
+//
+// This class replicates some menubar behaviors that are tricky to get right.
+// It is used to create a more native feel for the bookmark bar and the
+// page/app menus.
+
+#ifndef CHROME_BROWSER_GTK_MENU_BAR_HELPER_H_
+#define CHROME_BROWSER_GTK_MENU_BAR_HELPER_H_
+
+#include <gtk/gtk.h>
+
+#include <vector>
+
+class MenuBarHelper {
+ public:
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+
+    // Called when a the menu for a button ought to be triggered.
+    virtual void PopupForButton(GtkWidget* button) = 0;
+    virtual void PopupForButtonNextTo(GtkWidget* button,
+                                      GtkMenuDirectionType dir) = 0;
+  };
+
+  // |delegate| cannot be null.
+  explicit MenuBarHelper(Delegate* delegate);
+  ~MenuBarHelper();
+
+  // Must be called whenever a button's menu starts showing. It triggers the
+  // MenuBarHelper to start listening for certain events.
+  void MenuStartedShowing(GtkWidget* button, GtkWidget* menu);
+
+  // Add |button| to the set of buttons we care about.
+  void Add(GtkWidget* button);
+
+  // Remove |button| from the set of buttons we care about.
+  void Remove(GtkWidget* button);
+
+  // Clear all buttons from the set.
+  void Clear();
+
+ private:
+  static gboolean OnMenuMotionNotifyThunk(GtkWidget* menu,
+                                          GdkEventMotion* motion,
+                                          MenuBarHelper* helper) {
+    return helper->OnMenuMotionNotify(menu, motion);
+  }
+  gboolean OnMenuMotionNotify(GtkWidget* menu, GdkEventMotion* motion);
+
+  static void OnMenuHiddenThunk(GtkWidget* menu, MenuBarHelper* helper) {
+    helper->OnMenuHidden(menu);
+  }
+  void OnMenuHidden(GtkWidget* menu);
+
+  static void OnMenuMoveCurrentThunk(GtkWidget* menu,
+                                     GtkMenuDirectionType dir,
+                                     MenuBarHelper* helper) {
+    helper->OnMenuMoveCurrent(menu, dir);
+  }
+  void OnMenuMoveCurrent(GtkWidget* menu, GtkMenuDirectionType dir);
+
+  // The buttons for which we pop up menus. We do not own these, or even add
+  // refs to them.
+  std::vector<GtkWidget*> buttons_;
+
+  // The button that is currently showing a menu, or NULL.
+  GtkWidget* button_showing_menu_;
+
+  // The highest level menu that is currently showing, or NULL.
+  GtkWidget* showing_menu_;
+
+  // All the submenus of |showing_menu_|. We connect to motion events on all
+  // of them.
+  std::vector<GtkWidget*> submenus_;
+
+  Delegate* delegate_;
+};
+
+#endif  // CHROME_BROWSER_GTK_MENU_BAR_HELPER_H_