Makes it so that when a folder is open on the bookmark bar and the

mouse moves over another folder, the menu for that folder is shown.

BUG=355
TEST=thorougly test all possible permutations of bookmark menus you
     can think of, including drag and drop to the menus.

Review URL: http://codereview.chromium.org/328012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@30049 0039d316-1c4b-4281-b951-d872f2087c98

14 files changed, 202 insertions, 84 deletions

diff --git a/views/controls/button/menu_button.cc b/views/controls/button/menu_button.cc
index 5dc59cb..e457304 100644
--- a/views/controls/button/menu_button.cc
+++ b/views/controls/button/menu_button.cc
@@ -47,7 +47,6 @@ MenuButton::MenuButton(ButtonListener* listener,
                        bool show_menu_marker)
     : TextButton(listener, text),
       menu_visible_(false),
-      menu_closed_time_(),
       menu_delegate_(menu_delegate),
       show_menu_marker_(show_menu_marker) {
   if (kMenuMarker == NULL) {
diff --git a/views/controls/menu/menu_controller.cc b/views/controls/menu/menu_controller.cc
index 6175e62..4388d91 100644
--- a/views/controls/menu/menu_controller.cc
+++ b/views/controls/menu/menu_controller.cc
@@ -9,6 +9,7 @@
 #include "app/os_exchange_data.h"
 #include "base/keyboard_codes.h"
 #include "base/time.h"
+#include "views/controls/button/menu_button.h"
 #include "views/controls/menu/menu_scroll_view_container.h"
 #include "views/controls/menu/submenu_view.h"
 #include "views/drag_utils.h"
@@ -143,6 +144,7 @@ static int nested_depth = 0;
 #endif
 
 MenuItemView* MenuController::Run(gfx::NativeWindow parent,
+                                  MenuButton* button,
                                   MenuItemView* root,
                                   const gfx::Rect& bounds,
                                   MenuItemView::AnchorPosition position,
@@ -168,19 +170,9 @@ MenuItemView* MenuController::Run(gfx::NativeWindow parent,
   // Reset current state.
   pending_state_ = State();
   state_ = State();
-  pending_state_.initial_bounds = bounds;
-  if (bounds.height() > 1) {
-    // Inset the bounds slightly, otherwise drag coordinates don't line up
-    // nicely and menus close prematurely.
-    pending_state_.initial_bounds.Inset(0, 1);
-  }
-  pending_state_.anchor = position;
-  owner_ = parent;
+  UpdateInitialLocation(bounds, position);
 
-  // Calculate the bounds of the monitor we'll show menus on. Do this once to
-  // avoid repeated system queries for the info.
-  pending_state_.monitor_bounds = Screen::GetMonitorAreaNearestPoint(
-      bounds.origin());
+  owner_ = parent;
 
   // Set the selection, which opens the initial menu.
   SetSelection(root, true, true);
@@ -190,6 +182,8 @@ MenuItemView* MenuController::Run(gfx::NativeWindow parent,
     // notification when the drag has finished.
     StartCancelAllTimer();
     return NULL;
+  } else if (button) {
+    menu_button_ = button;
   }
 
 #ifdef DEBUG_MENU
@@ -245,6 +239,11 @@ MenuItemView* MenuController::Run(gfx::NativeWindow parent,
     exit_all_ = true;
   }
 
+  if (menu_button_) {
+    menu_button_->SetState(CustomButton::BS_NORMAL);
+    menu_button_->SchedulePaint();
+  }
+
   return result;
 }
 
@@ -316,8 +315,7 @@ void MenuController::OnMousePressed(SubmenuView* source,
   if (!blocking_run_)
     return;
 
-  MenuPart part =
-      GetMenuPartByScreenCoordinate(source, event.x(), event.y());
+  MenuPart part = GetMenuPartByScreenCoordinate(source, event.x(), event.y());
   if (part.is_scroll())
     return;  // Ignore presses on scroll buttons.
 
@@ -362,8 +360,7 @@ void MenuController::OnMouseDragged(SubmenuView* source,
 #ifdef DEBUG_MENU
   DLOG(INFO) << "OnMouseDragged source=" << source;
 #endif
-  MenuPart part =
-      GetMenuPartByScreenCoordinate(source, event.x(), event.y());
+  MenuPart part = GetMenuPartByScreenCoordinate(source, event.x(), event.y());
   UpdateScrolling(part);
 
   if (!blocking_run_)
@@ -409,6 +406,8 @@ void MenuController::OnMouseDragged(SubmenuView* source,
     if (!part.menu)
       part.menu = source->GetMenuItem();
     SetSelection(part.menu ? part.menu : state_.item, true, false);
+  } else if (part.type == MenuPart::NONE) {
+    ShowSiblingMenu(source, event);
   }
 }
 
@@ -423,8 +422,7 @@ void MenuController::OnMouseReleased(SubmenuView* source,
   DCHECK(state_.item);
   possible_drag_ = false;
   DCHECK(blocking_run_);
-  MenuPart part =
-      GetMenuPartByScreenCoordinate(source, event.x(), event.y());
+  MenuPart part = GetMenuPartByScreenCoordinate(source, event.x(), event.y());
   if (event.IsRightMouseButton() && (part.type == MenuPart::MENU_ITEM &&
                                      part.menu)) {
     // Set the selection immediately, making sure the submenu is only open
@@ -460,14 +458,16 @@ void MenuController::OnMouseMoved(SubmenuView* source,
   if (showing_submenu_)
     return;
 
-  MenuPart part =
-      GetMenuPartByScreenCoordinate(source, event.x(), event.y());
+  MenuPart part = GetMenuPartByScreenCoordinate(source, event.x(), event.y());
 
   UpdateScrolling(part);
 
   if (!blocking_run_)
     return;
 
+  if (part.type == MenuPart::NONE && ShowSiblingMenu(source, event))
+    return;
+
   if (part.type == MenuPart::MENU_ITEM && part.menu) {
     SetSelection(part.menu, true, false);
   } else if (!part.is_scroll() && pending_state_.item &&
@@ -803,7 +803,8 @@ MenuController::MenuController(bool blocking)
       owner_(NULL),
       possible_drag_(false),
       valid_drop_coordinates_(false),
-      showing_submenu_(false) {
+      showing_submenu_(false),
+      menu_button_(NULL) {
 #ifdef DEBUG_MENU
   instance_count++;
   DLOG(INFO) << "created MC, count=" << instance_count;
@@ -820,6 +821,23 @@ MenuController::~MenuController() {
 #endif
 }
 
+void MenuController::UpdateInitialLocation(
+    const gfx::Rect& bounds,
+    MenuItemView::AnchorPosition position) {
+  pending_state_.initial_bounds = bounds;
+  if (bounds.height() > 1) {
+    // Inset the bounds slightly, otherwise drag coordinates don't line up
+    // nicely and menus close prematurely.
+    pending_state_.initial_bounds.Inset(0, 1);
+  }
+  pending_state_.anchor = position;
+
+  // Calculate the bounds of the monitor we'll show menus on. Do this once to
+  // avoid repeated system queries for the info.
+  pending_state_.monitor_bounds = Screen::GetMonitorAreaNearestPoint(
+      bounds.origin());
+}
+
 void MenuController::Accept(MenuItemView* item, int mouse_event_flags) {
   DCHECK(IsBlockingRun());
   result_ = item;
@@ -827,6 +845,63 @@ void MenuController::Accept(MenuItemView* item, int mouse_event_flags) {
   result_mouse_event_flags_ = mouse_event_flags;
 }
 
+bool MenuController::ShowSiblingMenu(SubmenuView* source, const MouseEvent& e) {
+  if (!menu_stack_.empty() || !menu_button_)
+    return false;
+
+  View* source_view = source->GetScrollViewContainer();
+  if (e.x() >= 0 && e.x() < source_view->width() && e.y() >= 0 &&
+      e.y() < source_view->height()) {
+    // The mouse is over the menu, no need to continue.
+    return false;
+  }
+
+  gfx::NativeWindow window_under_mouse = Screen::GetWindowAtCursorScreenPoint();
+  if (window_under_mouse != owner_)
+    return false;
+
+  // The user moved the mouse outside the menu and over the owning window. See
+  // if there is a sibling menu we should show.
+  gfx::Point screen_point(e.location());
+  View::ConvertPointToScreen(source_view, &screen_point);
+  MenuItemView::AnchorPosition anchor;
+  bool has_mnemonics;
+  MenuButton* button = NULL;
+  MenuItemView* alt_menu = source->GetMenuItem()->GetDelegate()->
+      GetSiblingMenu(source->GetMenuItem()->GetRootMenuItem(),
+                     screen_point, &anchor, &has_mnemonics, &button);
+  if (!alt_menu || alt_menu == state_.item)
+    return false;
+
+  if (!button) {
+    // If the delegate returns a menu, they must also return a button.
+    NOTREACHED();
+    return false;
+  }
+
+  // There is a sibling menu, update the button state, hide the current menu
+  // and show the new one.
+  menu_button_->SetState(CustomButton::BS_NORMAL);
+  menu_button_->SchedulePaint();
+  menu_button_ = button;
+  menu_button_->SetState(CustomButton::BS_PUSHED);
+  menu_button_->SchedulePaint();
+
+  // Need to reset capture when we show the menu again, otherwise we aren't
+  // going to get any events.
+  did_capture_ = false;
+  gfx::Point screen_menu_loc;
+  View::ConvertPointToScreen(button, &screen_menu_loc);
+  // Subtract 1 from the height to make the popup flush with the button border.
+  UpdateInitialLocation(gfx::Rect(screen_menu_loc.x(), screen_menu_loc.y(),
+                                  button->width(), button->height() - 1),
+                        anchor);
+  alt_menu->PrepareForRun(has_mnemonics);
+  alt_menu->controller_ = this;
+  SetSelection(alt_menu, true, true);
+  return true;
+}
+
 void MenuController::CloseAllNestedMenus() {
   for (std::list<State>::iterator i = menu_stack_.begin();
        i != menu_stack_.end(); ++i) {
diff --git a/views/controls/menu/menu_controller.h b/views/controls/menu/menu_controller.h
index bc57036..2ef1bb7 100644
--- a/views/controls/menu/menu_controller.h
+++ b/views/controls/menu/menu_controller.h
@@ -22,6 +22,7 @@ class OSExchangeData;
 namespace views {
 
 class DropTargetEvent;
+class MenuButton;
 class MenuHostRootView;
 class MouseEvent;
 class SubmenuView;
@@ -44,6 +45,7 @@ class MenuController : public MessageLoopForUI::Dispatcher {
   // block, the selected item is returned. If the menu does not block this
   // returns NULL immediately.
   MenuItemView* Run(gfx::NativeWindow parent,
+                    MenuButton* button,
                     MenuItemView* root,
                     const gfx::Rect& bounds,
                     MenuItemView::AnchorPosition position,
@@ -182,10 +184,15 @@ class MenuController : public MessageLoopForUI::Dispatcher {
 
   ~MenuController();
 
+  void UpdateInitialLocation(const gfx::Rect& bounds,
+                             MenuItemView::AnchorPosition position);
+
   // Invoked when the user accepts the selected item. This is only used
   // when blocking. This schedules the loop to quit.
   void Accept(MenuItemView* item, int mouse_event_flags);
 
+  bool ShowSiblingMenu(SubmenuView* source, const MouseEvent& e);
+
   // Closes all menus, including any menus of nested invocations of Run.
   void CloseAllNestedMenus();
 
@@ -330,7 +337,7 @@ class MenuController : public MessageLoopForUI::Dispatcher {
   MenuItemView* result_;
 
   // The mouse event flags when the user clicked on a menu. Is 0 if the
-  // user did not use the mousee to select the menu.
+  // user did not use the mouse to select the menu.
   int result_mouse_event_flags_;
 
   // If not empty, it means we're nested. When Run is invoked from within
@@ -376,6 +383,8 @@ class MenuController : public MessageLoopForUI::Dispatcher {
   // underway.
   scoped_ptr<MenuScrollTask> scroll_task_;
 
+  MenuButton* menu_button_;
+
   DISALLOW_COPY_AND_ASSIGN(MenuController);
 };
 
diff --git a/views/controls/menu/menu_delegate.h b/views/controls/menu/menu_delegate.h
index ec66a4f..2f7cd66 100644
--- a/views/controls/menu/menu_delegate.h
+++ b/views/controls/menu/menu_delegate.h
@@ -12,12 +12,13 @@
 #include "app/os_exchange_data.h"
 #include "base/logging.h"
 #include "views/controls/menu/controller.h"
+#include "views/controls/menu/menu_item_view.h"
 #include "views/event.h"
 
 namespace views {
 
 class DropTargetEvent;
-class MenuItemView;
+class MenuButton;
 
 // MenuDelegate --------------------------------------------------------------
 
@@ -180,6 +181,19 @@ class MenuDelegate : Controller {
   // Notification that the user has highlighted the specified item.
   virtual void SelectionChanged(MenuItemView* menu) {
   }
+
+  // If the user drags the mouse outside the bounds of the menu the delegate
+  // is queried for a sibling menu to show. If this returns non-null the
+  // current menu is hidden, and the menu returned from this method is shown.
+  //
+  // The delegate owns the returned menu, not the controller.
+  virtual MenuItemView* GetSiblingMenu(MenuItemView* menu,
+                                       const gfx::Point& screen_point,
+                                       MenuItemView::AnchorPosition* anchor,
+                                       bool* has_mnemonics,
+                                       MenuButton** button) {
+      return NULL;
+  }
 };
 
 }  // namespace views
diff --git a/views/controls/menu/menu_host_gtk.cc b/views/controls/menu/menu_host_gtk.cc
index 11033c4..38945e5 100644
--- a/views/controls/menu/menu_host_gtk.cc
+++ b/views/controls/menu/menu_host_gtk.cc
@@ -19,14 +19,13 @@ MenuHost::MenuHost(SubmenuView* submenu)
       closed_(false),
       submenu_(submenu),
       did_pointer_grab_(false) {
-  GdkModifierType current_event_mod;
-  if (gtk_get_current_event_state(&current_event_mod)) {
-    set_mouse_down(
-        (current_event_mod & GDK_BUTTON1_MASK) ||
-        (current_event_mod & GDK_BUTTON2_MASK) ||
-        (current_event_mod & GDK_BUTTON3_MASK) ||
-        (current_event_mod & GDK_BUTTON4_MASK) ||
-        (current_event_mod & GDK_BUTTON5_MASK));
+  GdkEvent* event = gtk_get_current_event();
+  if (event) {
+    if (event->type == GDK_BUTTON_PRESS || event->type == GDK_2BUTTON_PRESS ||
+        event->type == GDK_3BUTTON_PRESS) {
+      set_mouse_down(true);
+    }
+    gdk_event_free(event);
   }
 }
 
@@ -36,33 +35,9 @@ void MenuHost::Init(gfx::NativeWindow parent,
                     bool do_capture) {
   WidgetGtk::Init(GTK_WIDGET(parent), bounds);
   SetContentsView(contents_view);
-  // TODO(sky): see if there is some way to show without changing focus.
   Show();
-  if (do_capture) {
-    // Release the current grab.
-    GtkWidget* current_grab_window = gtk_grab_get_current();
-    if (current_grab_window)
-      gtk_grab_remove(current_grab_window);
-
-    // Make sure all app mouse events are targetted at us only.
-    DoGrab();
-
-    // And do a grab.
-    // NOTE: we do this to ensure we get mouse events from other apps, a grab
-    // done with gtk_grab_add doesn't get events from other apps.
-    GdkGrabStatus grab_status =
-        gdk_pointer_grab(window_contents()->window, FALSE,
-                         static_cast<GdkEventMask>(
-                             GDK_BUTTON_PRESS_MASK | GDK_BUTTON_RELEASE_MASK |
-                             GDK_POINTER_MOTION_MASK),
-                         NULL, NULL, GDK_CURRENT_TIME);
-    did_pointer_grab_ = (grab_status == GDK_GRAB_SUCCESS);
-    DCHECK(did_pointer_grab_);
-    // need keyboard grab.
-#ifdef DEBUG_MENU
-    DLOG(INFO) << "Doing capture";
-#endif
-  }
+  if (do_capture)
+    DoCapture();
 }
 
 gfx::NativeWindow MenuHost::GetNativeWindow() {
@@ -95,6 +70,32 @@ void MenuHost::HideWindow() {
   WidgetGtk::Hide();
 }
 
+void MenuHost::DoCapture() {
+  // Release the current grab.
+  GtkWidget* current_grab_window = gtk_grab_get_current();
+  if (current_grab_window)
+    gtk_grab_remove(current_grab_window);
+
+  // Make sure all app mouse events are targetted at us only.
+  DoGrab();
+
+  // And do a grab.
+  // NOTE: we do this to ensure we get mouse events from other apps, a grab
+  // done with gtk_grab_add doesn't get events from other apps.
+  GdkGrabStatus grab_status =
+      gdk_pointer_grab(window_contents()->window, FALSE,
+                       static_cast<GdkEventMask>(
+                           GDK_BUTTON_PRESS_MASK | GDK_BUTTON_RELEASE_MASK |
+                           GDK_POINTER_MOTION_MASK),
+                       NULL, NULL, GDK_CURRENT_TIME);
+  did_pointer_grab_ = (grab_status == GDK_GRAB_SUCCESS);
+  DCHECK(did_pointer_grab_);
+  // need keyboard grab.
+#ifdef DEBUG_MENU
+  DLOG(INFO) << "Doing capture";
+#endif
+}
+
 void MenuHost::ReleaseCapture() {
   ReleaseGrab();
 }
diff --git a/views/controls/menu/menu_host_gtk.h b/views/controls/menu/menu_host_gtk.h
index 8e69ce8..4ae1b77 100644
--- a/views/controls/menu/menu_host_gtk.h
+++ b/views/controls/menu/menu_host_gtk.h
@@ -27,6 +27,7 @@ class MenuHost : public WidgetGtk {
   void Show();
   virtual void Hide();
   virtual void HideWindow();
+  void DoCapture();
   void ReleaseCapture();
 
  protected:
diff --git a/views/controls/menu/menu_host_win.cc b/views/controls/menu/menu_host_win.cc
index d6fd655..f2c2c2c 100644
--- a/views/controls/menu/menu_host_win.cc
+++ b/views/controls/menu/menu_host_win.cc
@@ -37,14 +37,8 @@ void MenuHost::Init(HWND parent,
   WidgetWin::Init(parent, bounds);
   SetContentsView(contents_view);
   Show();
-  owns_capture_ = do_capture;
-  if (do_capture) {
-    SetCapture();
-    has_capture_ = true;
-#ifdef DEBUG_MENU
-    DLOG(INFO) << "Doing capture";
-#endif
-  }
+  if (do_capture)
+    DoCapture();
 }
 
 void MenuHost::Show() {
@@ -82,6 +76,15 @@ void MenuHost::OnCaptureChanged(HWND hwnd) {
 #endif
 }
 
+void MenuHost::DoCapture() {
+  owns_capture_ = true;
+  SetCapture();
+  has_capture_ = true;
+#ifdef DEBUG_MENU
+  DLOG(INFO) << "Doing capture";
+#endif
+}
+
 void MenuHost::ReleaseCapture() {
   if (owns_capture_) {
 #ifdef DEBUG_MENU
diff --git a/views/controls/menu/menu_host_win.h b/views/controls/menu/menu_host_win.h
index 6e645d2..ec5d060 100644
--- a/views/controls/menu/menu_host_win.h
+++ b/views/controls/menu/menu_host_win.h
@@ -28,6 +28,7 @@ class MenuHost : public WidgetWin {
   virtual void Hide();
   virtual void HideWindow();
   virtual void OnCaptureChanged(HWND hwnd);
+  void DoCapture();
   void ReleaseCapture();
 
  protected:
diff --git a/views/controls/menu/menu_item_view.cc b/views/controls/menu/menu_item_view.cc
index 4d5b3ae..2734788 100644
--- a/views/controls/menu/menu_item_view.cc
+++ b/views/controls/menu/menu_item_view.cc
@@ -66,23 +66,15 @@ MenuItemView::MenuItemView(MenuDelegate* delegate) {
 }
 
 MenuItemView::~MenuItemView() {
-  if (controller_) {
-    // We're currently showing.
-
-    // We can't delete ourselves while we're blocking.
-    DCHECK(!controller_->IsBlockingRun());
-
-    // Invoking Cancel is going to call us back and notify the delegate.
-    // Notifying the delegate from the destructor can be problematic. To avoid
-    // this the delegate is set to NULL.
-    delegate_ = NULL;
-
-    controller_->Cancel(true);
-  }
+  // TODO(sky): ownership is bit wrong now. In particular if a nested message
+  // loop is running deletion can't be done, otherwise the stack gets
+  // thoroughly screwed. The destructor should be made private, and
+  // MenuController should be the only place handling deletion of the menu.
   delete submenu_;
 }
 
 void MenuItemView::RunMenuAt(gfx::NativeWindow parent,
+                             MenuButton* button,
                              const gfx::Rect& bounds,
                              AnchorPosition anchor,
                              bool has_mnemonics) {
@@ -115,7 +107,7 @@ void MenuItemView::RunMenuAt(gfx::NativeWindow parent,
 
   // Run the loop.
   MenuItemView* result =
-      controller->Run(parent, this, bounds, anchor, &mouse_event_flags);
+      controller->Run(parent, button, this, bounds, anchor, &mouse_event_flags);
 
   RemoveEmptyMenus();
 
@@ -151,7 +143,7 @@ void MenuItemView::RunMenuForDropAt(gfx::NativeWindow parent,
   // Set the instance, that way it can be canceled by another menu.
   MenuController::SetActiveInstance(controller_);
 
-  controller_->Run(parent, this, bounds, anchor, NULL);
+  controller_->Run(parent, NULL, this, bounds, anchor, NULL);
 }
 
 void MenuItemView::Cancel() {
@@ -337,9 +329,6 @@ void MenuItemView::PrepareForRun(bool has_mnemonics) {
   // Currently we only support showing the root.
   DCHECK(!parent_menu_item_);
 
-  // Don't invoke run from within run on the same menu.
-  DCHECK(!controller_);
-
   // Force us to have a submenu.
   CreateSubmenu();
 
diff --git a/views/controls/menu/menu_item_view.h b/views/controls/menu/menu_item_view.h
index ecb3b78..a85e265 100644
--- a/views/controls/menu/menu_item_view.h
+++ b/views/controls/menu/menu_item_view.h
@@ -10,6 +10,7 @@
 
 namespace views {
 
+class MenuButton;
 class MenuController;
 class MenuDelegate;
 class SubmenuView;
@@ -82,6 +83,7 @@ class MenuItemView : public View {
   // whether the items have mnemonics. Mnemonics are identified by way of the
   // character following the '&'.
   void RunMenuAt(gfx::NativeWindow parent,
+                 MenuButton* button,
                  const gfx::Rect& bounds,
                  AnchorPosition anchor,
                  bool has_mnemonics);
diff --git a/views/controls/menu/submenu_view.cc b/views/controls/menu/submenu_view.cc
index d08de6f..3b315ef 100644
--- a/views/controls/menu/submenu_view.cc
+++ b/views/controls/menu/submenu_view.cc
@@ -221,6 +221,8 @@ void SubmenuView::ShowAt(gfx::NativeWindow parent,
                          bool do_capture) {
   if (host_) {
     host_->Show();
+    if (do_capture)
+      host_->DoCapture();
     return;
   }
 
diff --git a/views/screen.h b/views/screen.h
index f7c023c..f95b368 100644
--- a/views/screen.h
+++ b/views/screen.h
@@ -27,6 +27,9 @@ class Screen {
   // Returns the monitor area (not the work area, but the complete bounds) of
   // the monitor nearest the specified point.
   static gfx::Rect GetMonitorAreaNearestPoint(const gfx::Point& point);
+
+  // Returns the window under the cursor.
+  static gfx::NativeWindow GetWindowAtCursorScreenPoint();
 };
 
 }  // namespace views
diff --git a/views/screen_gtk.cc b/views/screen_gtk.cc
index 9302853..a0daa19 100644
--- a/views/screen_gtk.cc
+++ b/views/screen_gtk.cc
@@ -58,5 +58,19 @@ gfx::Rect Screen::GetMonitorAreaNearestPoint(const gfx::Point& point) {
   return gfx::Rect(bounds);
 }
 
+gfx::NativeWindow Screen::GetWindowAtCursorScreenPoint() {
+  GdkWindow* window = gdk_window_at_pointer(NULL, NULL);
+  if (!window)
+    return NULL;
+
+  gpointer data = NULL;
+  gdk_window_get_user_data(window, &data);
+  GtkWidget* widget = reinterpret_cast<GtkWidget*>(data);
+  if (!widget)
+    return NULL;
+  widget = gtk_widget_get_toplevel(widget);
+  return GTK_IS_WINDOW(widget) ? GTK_WINDOW(widget) : NULL;
+}
+
 }  // namespace
 
diff --git a/views/screen_win.cc b/views/screen_win.cc
index 82e95e6..4ddb7c1 100644
--- a/views/screen_win.cc
+++ b/views/screen_win.cc
@@ -46,5 +46,10 @@ gfx::Rect Screen::GetMonitorAreaNearestPoint(const gfx::Point& point) {
   return gfx::Rect(mi.rcMonitor);
 }
 
+gfx::NativeWindow Screen::GetWindowAtCursorScreenPoint() {
+  POINT location;
+  return GetCursorPos(&location) ? WindowFromPoint(location) : NULL;
+}
+
 }  // namespace