Make info button appear only when mouse is over the panel or the panel has focus.

chrome/browser/ui/panels/panel_browser_frame_view.h

 // Copyright (c) 2011 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.
 
 #ifndef CHROME_BROWSER_UI_PANELS_PANEL_BROWSER_FRAME_VIEW_H_
 #define CHROME_BROWSER_UI_PANELS_PANEL_BROWSER_FRAME_VIEW_H_
 #pragma once
 
 #include "base/gtest_prod_util.h"
+#include "base/message_loop.h"
 #include "base/scoped_ptr.h"
 #include "chrome/browser/ui/views/frame/browser_non_client_frame_view.h"
 #include "chrome/browser/ui/views/tab_icon_view.h"
 #include "views/controls/button/button.h"
 
 class PanelBrowserView;
 namespace views {
 class ImageButton;
 class Label;
 }
@@ skipping 46 matching lines @@
  private:
   friend class PanelBrowserViewTest;
   FRIEND_TEST_ALL_PREFIXES(PanelBrowserViewTest, CreatePanel);
 
   enum PaintState {
     NOT_PAINTED,
     PAINT_AS_INACTIVE,
     PAINT_AS_ACTIVE
   };
 
+  class MouseWatcher : public MessageLoopForUI::Observer {

[jennb, 2011/05/20 23:13:12]

Did you look at using views/mouse_watcher.h?  MouseWatcher only notifies
listener when mouse moves outside of view. Do we really need to watch both
mouse-enter and mouse-leave?  TabStrip uses MouseWatcherListener and yet tab is
able to change appearance when mouse moves in and out of the tab so it looks
like it should be sufficient.

[jianli, 2011/05/23 21:21:03]

Yes, I've looked at views/mouse_watcher.* to see if I can reuse it.
Unfortunately it is only for mouse leaving and we would add up much more
complexity to it if we want also to support mouse entering. So I rather put our
mouse watching logic in panel code since the panel is the only user. If we have
other scenario needing this in the future, I am happy to refactor it.

The code to change appearance when mouse moves in and out of the tab is in
base_tab.cc (OnMouseEntered and OnMouseExited). This approach did not work in
our panel case for the following reasons:
1) For non-client view, we need to hook up with OnMouseEntered and OnMouseExited
for PanelBrowserFrameView, its view for close button, and its view for info
button. This is because when we move the mouse  from non-close-button area to
close-button area in the title bar, PanelBrowserFrameView gets triggered with
OnMouseExited and the view for close button gets triggered with OnMouseEntered.
This is a bit complicated but it is doable.,
2) For client view,  OnMouseEntered and OnMouseExited are not called at all. I
think this is by design. So we have no way to listen to mouse entering and mouse
exiting event for client view. Even we get notified, we might hard time to
coordinate events from non-client view and client view.

So what I do here seems to be a only reliable way to detect if the mouse moves
in to or out of a panel window, including both non-client view and client view.

+   public:
+    explicit MouseWatcher(PanelBrowserFrameView* view);
+    virtual ~MouseWatcher();
+
+    virtual bool IsCursorInViewBounds() const;
+
+  #if defined(OS_WIN)
+    virtual void WillProcessMessage(const MSG& msg) OVERRIDE { }
+    virtual void DidProcessMessage(const MSG& msg) OVERRIDE;
+  #else
+    virtual void WillProcessEvent(GdkEvent* event) OVERRIDE { }
+    virtual void DidProcessEvent(GdkEvent* event) OVERRIDE;
+  #endif
+
+   private:
+    void HandleGlobalMouseMoveEvent();
+
+    PanelBrowserFrameView* view_;
+    bool in_view_;
+
+    DISALLOW_COPY_AND_ASSIGN(MouseWatcher);
+  };
+
   // Returns the thickness of the entire nonclient left, right, and bottom
   // borders, including both the window frame and any client edge.
   int NonClientBorderThickness() const;
 
   // Returns the height of the entire nonclient top border, including the window
   // frame, any title area, and any connected client edge.
   int NonClientTopBorderHeight() const;
 
   // Update control styles to indicate if the title bar is active or not.
   void UpdateControlStyles(PaintState paint_state);
 
   // Custom draw the frame.
   void PaintFrameBorder(gfx::Canvas* canvas);
   void PaintClientEdge(gfx::Canvas* canvas);
 
+  // Called by MouseWatcher to notify if the mouse enters or leaves the window.
+  void OnMouseEnterOrLeaveWindow(bool mouse_entered);
+
+  // Make info button visible if either of the conditions is met:
+  // 1) The panel is active, i.e. having focus.
+  // 2) The mouse is over the panel.
+  void UpdateInfoButtonVisibility(bool active, bool cursor_in_view);
+
+#ifdef UNIT_TEST
+  void set_mouse_watcher(MouseWatcher* mouse_watcher) {
+    mouse_watcher_.reset(mouse_watcher);
+  }
+#endif
+
   // The frame that hosts this view. This is a weak reference such that frame_
   // will always be valid in the lifetime of this view.
   BrowserFrame* frame_;
 
   // The client view hosted within this non-client frame view that is
   // guaranteed to be freed before the client view.
   // (see comments about view hierarchies in non_client_view.h)
   PanelBrowserView* browser_view_;
 
   PaintState paint_state_;
   views::ImageButton* info_button_;
   views::ImageButton* close_button_;
   TabIconView* title_icon_;
   views::Label* title_label_;
   gfx::Rect client_view_bounds_;
+  scoped_ptr<MouseWatcher> mouse_watcher_;
 
   DISALLOW_COPY_AND_ASSIGN(PanelBrowserFrameView);
 };
 
 #endif  // CHROME_BROWSER_UI_PANELS_PANEL_BROWSER_FRAME_VIEW_H_