Moves the notification icon out of the status area overflow.

chrome/browser/ui/views/status_icons/status_tray_state_changer_win.h

+// Copyright 2014 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_VIEWS_STATUS_ICONS_STATUS_TRAY_STATE_CHANGER_WIN_H_

[sky, 2014/04/04 21:13:25]

I'm assuming cpu reviewed all this code.

+#define CHROME_BROWSER_UI_VIEWS_STATUS_ICONS_STATUS_TRAY_STATE_CHANGER_WIN_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "base/strings/string16.h"
+#include "base/threading/non_thread_safe.h"
+#include "base/win/iunknown_impl.h"
+#include "base/win/scoped_comptr.h"
+
+// The known values for NOTIFYITEM's dwPreference member.
+enum NOTIFYITEM_PREFERENCE {
+  // In Windows UI: "Only show notifications."
+  PREFERENCE_SHOW_WHEN_ACTIVE = 0,
+  // In Windows UI: "Hide icon and notifications."
+  PREFERENCE_SHOW_NEVER = 1,
+  // In Windows UI: "Show icon and notifications."
+  PREFERENCE_SHOW_ALWAYS = 2
+};
+
+// NOTIFYITEM describes an entry in Explorer's registry of status icons.
+// Explorer keeps entries around for a process even after it exits.
+struct NOTIFYITEM {
+  PWSTR pszExeName;  // The file name of the creating executable.

[sky, 2014/04/04 21:13:25]

Even though I'm assuming cpu reviewed all this, how come these members don't
follow style guide convension, eg psz_exe_name?

[dewittj, 2014/04/04 22:35:57]

I guess I thought that in windows data structures we'd use windows-style names. 
I changed them.

+  PWSTR pszTip;  // The last hover-text value associated with this status item.
+  HICON hIcon;   // The icon associated with this status item.
+  HWND hWnd;     // The HWND associated with the status item.
+  DWORD dwPreference;  // Determines the behavior of the icon with respect to
+                       // the taskbar. Values taken from NOTIFYITEM_PREFERENCE.
+  UINT uID;  // The ID specified by the application.  (hWnd, uID) is unique.
+  GUID guidItem;  // The GUID specified by the application, alternative to uID.
+};
+
+// INotificationCB is an interface that applications can implement in order to
+// receive notifications about the state of the notification area manager.
+class __declspec(uuid("D782CCBA-AFB0-43F1-94DB-FDA3779EACCB")) INotificationCB
+    : public IUnknown {
+ public:
+  virtual HRESULT STDMETHODCALLTYPE
+      Notify(ULONG event, NOTIFYITEM* notify_item) = 0;
+};
+
+// A class that is capable of reading and writing the state of the notification
+// area in the Windows taskbar.  It is used to promote a tray icon from the
+// overflow area to the taskbar, and refuses to do anything if the user has
+// explicitly marked an icon to be always hidden.
+class StatusTrayStateChangerWin : public INotificationCB,
+                                  public base::win::IUnknownImpl,
+                                  public base::NonThreadSafe {
+ public:
+  StatusTrayStateChangerWin(UINT icon_id, HWND window);
+
+  // Call this method to move the icon matching |icon_id| and |window| to the
+  // taskbar from the overflow area.  This will not make any changes if the
+  // icon has been set to |PREFERENCE_SHOW_NEVER|, in order to comply with
+  // the explicit wishes/configuration of the user.
+  void EnsureTrayIconVisible();
+
+  // IUnknown.
+  virtual ULONG STDMETHODCALLTYPE AddRef() OVERRIDE;
+  virtual ULONG STDMETHODCALLTYPE Release() OVERRIDE;
+  virtual HRESULT STDMETHODCALLTYPE QueryInterface(REFIID, PVOID*) OVERRIDE;
+
+  // INotificationCB.
+  // Notify is called in response to RegisterCallback for each current
+  // entry in Explorer's list of notification area icons, and ever time
+  // one of them changes, until UnregisterCallback is called or |this|
+  // is destroyed.
+  virtual HRESULT STDMETHODCALLTYPE Notify(ULONG, NOTIFYITEM*);
+
+ protected:
+  virtual ~StatusTrayStateChangerWin();
+
+ private:
+  friend class StatusTrayStateChangerWinTest;
+
+  enum InterfaceVersion {
+    INTERFACE_VERSION_LEGACY = 0,
+    INTERFACE_VERSION_WIN8,
+    INTERFACE_VERSION_UNKNOWN
+  };
+
+  // Creates an instance of TrayNotify, and ensures that it supports either
+  // ITrayNotify or ITrayNotifyWin8.  Returns true on success.
+  bool CreateTrayNotify();
+
+  // Returns the NOTIFYITEM that corresponds to this executable and the
+  // HWND/ID pair that were used to create the StatusTrayStateChangerWin.
+  // Internally it calls the appropriate RegisterCallback{Win8,Legacy}.
+  scoped_ptr<NOTIFYITEM> RegisterCallback();
+
+  // Calls RegisterCallback with the appropriate interface required by
+  // different versions of Windows.  This will result in |notify_item_| being
+  // updated when a matching item is passed into
+  // StatusTrayStateChangerWin::Notify.
+  bool RegisterCallbackWin8();
+  bool RegisterCallbackLegacy();
+
+  // Sends an update to Explorer with the passed NOTIFYITEM.
+  void SendNotifyItemUpdate(scoped_ptr<NOTIFYITEM> notify_item);
+
+  // Storing IUnknown since we will need to use different interfaces
+  // for different versions of Windows.
+  base::win::ScopedComPtr<IUnknown> tray_notify_;
+  InterfaceVersion interface_version_;
+
+  // The ID assigned to the notification area icon that we want to manipulate.
+  const UINT icon_id_;
+  // The HWND associated with the notification area icon that we want to
+  // manipulate.  This is an unretained pointer, do not dereference.
+  const HWND window_;
+  // Executable name of the current program.  Along with |icon_id_| and
+  // |window_|, this uniquely identifies a notification area entry to Explorer.
+  base::string16 file_name_;
+
+  // Temporary storage for the matched NOTIFYITEM.  This is necessary because
+  // Notify doesn't return anything.  The call flow looks like this:
+  //   TrayNotify->RegisterCallback()
+  //      ... other COM stack frames ..
+  //   StatusTrayStateChangerWin->Notify(NOTIFYITEM);
+  // so we can't just return the notifyitem we're looking for.
+  scoped_ptr<NOTIFYITEM> notify_item_;
+
+  DISALLOW_COPY_AND_ASSIGN(StatusTrayStateChangerWin);
+};
+
+#endif  // CHROME_BROWSER_UI_VIEWS_STATUS_ICONS_STATUS_TRAY_STATE_CHANGER_WIN_H_