Moved code implementing message-only windows to a dedicated class (Windows only).

remoting/host/win/message_window.cc

+// Copyright 2013 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.
+
+#include "remoting/host/win/message_window.h"
+
+#include "base/logging.h"
+#include "base/process_util.h"
+#include "base/stringprintf.h"
+#include "base/utf_string_conversions.h"
+#include "base/win/wrapped_window_proc.h"
+
+const char kClassNameFormat[] = "Chromoting_MessageWindow_%p";
+
+namespace remoting {
+namespace win {
+
+MessageWindow::MessageWindow()
+    : atom_(0),
+      instance_(NULL),
+      window_(NULL) {
+  class_name_ = base::StringPrintf(kClassNameFormat, this);
+  instance_ = base::GetModuleFromAddress(static_cast<WNDPROC>(
+      &base::win::WrappedWindowProc<WindowProc>));
+}
+
+MessageWindow::MessageWindow(const std::string& class_name, HINSTANCE instance)
+    : atom_(0),
+      class_name_(class_name),
+      instance_(instance),
+      window_(NULL) {
+}
+
+MessageWindow::~MessageWindow() {
+  DCHECK(CalledOnValidThread());
+
+  if (window_ != NULL) {
+    DestroyWindow(window_);
+    window_ = NULL;
+  }
+
+  if (atom_ != 0) {
+    UnregisterClass(MAKEINTATOM(atom_), instance_);
+    atom_ = 0;
+  }
+}
+
+bool MessageWindow::Create(Delegate* delegate) {
+  DCHECK(CalledOnValidThread());
+  DCHECK(!atom_);
+  DCHECK(!window_);
+
+  // Register a separate window class for each instance of |MessageWindow|.
+  string16 class_name = UTF8ToUTF16(class_name_);
+  WNDCLASSEX window_class;
+  window_class.cbSize = sizeof(window_class);
+  window_class.style = 0;
+  window_class.lpfnWndProc = &base::win::WrappedWindowProc<WindowProc>;
+  window_class.cbClsExtra = 0;
+  window_class.cbWndExtra = 0;
+  window_class.hInstance = instance_;
+  window_class.hIcon = NULL;
+  window_class.hCursor = NULL;
+  window_class.hbrBackground = NULL;
+  window_class.lpszMenuName = NULL;
+  window_class.lpszClassName = class_name.c_str();
+  window_class.hIconSm = NULL;
+  atom_ = RegisterClassEx(&window_class);
+  if (atom_ == 0) {
+    LOG_GETLASTERROR(ERROR)
+        << "Failed to register the window class '" << class_name_ << "'";
+    return false;
+  }
+
+  window_ = CreateWindow(MAKEINTATOM(atom_), 0, 0, 0, 0, 0, 0, HWND_MESSAGE, 0,
+                         instance_, delegate);
+  if (window_ == NULL) {
+    LOG_GETLASTERROR(ERROR) << "Failed to create a message-only window";
+    return false;
+  }
+
+  return true;
+}
+
+// static
+LRESULT CALLBACK MessageWindow::WindowProc(HWND hwnd,
+                                           UINT message,
+                                           WPARAM wparam,
+                                           LPARAM lparam) {
+  // Store |this| to the window's user data.

[dcaiafa, 2013/03/28 23:25:35]

You're actually storing delegate here, not |this|. I'd consider storing |this|,
as the comment currently states, and use it to set window_ on WM_CREATE. I think
it's simpler for the delegate if hwnd() is available on WM_CREATE.

[alexeypa (please no reviews), 2013/03/29 16:57:01]

Done.

+  if (message == WM_CREATE) {
+    CREATESTRUCT* cs = reinterpret_cast<CREATESTRUCT*>(lparam);
+    SetLastError(ERROR_SUCCESS);
+    LONG_PTR result = SetWindowLongPtr(
+        hwnd, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(cs->lpCreateParams));
+    CHECK(result != 0 || GetLastError() == ERROR_SUCCESS);
+  }
+
+  // Handle the message.
+  Delegate* delegate = reinterpret_cast<Delegate*>(
+      GetWindowLongPtr(hwnd, GWLP_USERDATA));
+  if (delegate) {
+    LRESULT result;
+    if (delegate->HandleMessage(message, wparam, lparam, &result))
+      return result;
+  }
+
+  return DefWindowProc(hwnd, message, wparam, lparam);
+}
+
+}  // namespace win
+}  // namespace remoting