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      1 // Copyright 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef BASE_WIN_MESSAGE_WINDOW_H_
      6 #define BASE_WIN_MESSAGE_WINDOW_H_
      7 
      8 #include <windows.h>
      9 
     10 #include "base/base_export.h"
     11 #include "base/basictypes.h"
     12 #include "base/callback.h"
     13 #include "base/compiler_specific.h"
     14 #include "base/strings/string16.h"
     15 #include "base/threading/non_thread_safe.h"
     16 
     17 namespace base {
     18 namespace win {
     19 
     20 // Implements a message-only window.
     21 class BASE_EXPORT MessageWindow : public base::NonThreadSafe {
     22  public:
     23   // Used to register a process-wide message window class.
     24   class WindowClass;
     25 
     26   // Implement this callback to handle messages received by the message window.
     27   // If the callback returns |false|, the first four parameters are passed to
     28   // DefWindowProc(). Otherwise, |*result| is returned by the window procedure.
     29   typedef base::Callback<bool(UINT message,
     30                               WPARAM wparam,
     31                               LPARAM lparam,
     32                               LRESULT* result)> MessageCallback;
     33 
     34   MessageWindow();
     35   ~MessageWindow();
     36 
     37   // Creates a message-only window. The incoming messages will be passed by
     38   // |message_callback|. |message_callback| must outlive |this|.
     39   bool Create(const MessageCallback& message_callback);
     40 
     41   // Same as Create() but assigns the name to the created window.
     42   bool CreateNamed(const MessageCallback& message_callback,
     43                    const string16& window_name);
     44 
     45   HWND hwnd() const { return window_; }
     46 
     47   // Retrieves a handle of the first message-only window with matching
     48   // |window_name|.
     49   static HWND FindWindow(const string16& window_name);
     50 
     51  private:
     52   // Give |WindowClass| access to WindowProc().
     53   friend class WindowClass;
     54 
     55   // Contains the actual window creation code.
     56   bool DoCreate(const MessageCallback& message_callback,
     57                 const wchar_t* window_name);
     58 
     59   // Invoked by the OS to process incoming window messages.
     60   static LRESULT CALLBACK WindowProc(HWND hwnd, UINT message, WPARAM wparam,
     61                                      LPARAM lparam);
     62 
     63   // Invoked to handle messages received by the window.
     64   MessageCallback message_callback_;
     65 
     66   // Handle of the input window.
     67   HWND window_;
     68 
     69   DISALLOW_COPY_AND_ASSIGN(MessageWindow);
     70 };
     71 
     72 }  // namespace win
     73 }  // namespace base
     74 
     75 #endif  // BASE_WIN_MESSAGE_WINDOW_H_
     76