ui::Clipboard now uses base::win::MessageWindow to create a message-only window on Windows.

ui/base/clipboard/clipboard_win.cc

Index: ui/base/clipboard/clipboard_win.cc
diff --git a/ui/base/clipboard/clipboard_win.cc b/ui/base/clipboard/clipboard_win.cc
index 47a97d90bbcd5efbadfafba5eaa75e313cfa851e..721b1311b5a3c545fdcf411603d2d5e9324b1338 100644
--- a/ui/base/clipboard/clipboard_win.cc
+++ b/ui/base/clipboard/clipboard_win.cc
@@ -21,6 +21,7 @@
 #include "base/strings/string_util.h"
 #include "base/strings/utf_offset_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/win/message_window.h"
 #include "base/win/scoped_gdi_object.h"
 #include "base/win/scoped_hdc.h"
 #include "base/win/wrapped_window_proc.h"
@@ -94,37 +95,6 @@ class ScopedClipboard {
   bool opened_;
 };
 
-LRESULT CALLBACK ClipboardOwnerWndProc(HWND hwnd,
-                                       UINT message,
-                                       WPARAM wparam,
-                                       LPARAM lparam) {
-  LRESULT lresult = 0;
-
-  switch (message) {
-  case WM_RENDERFORMAT:
-    // This message comes when SetClipboardData was sent a null data handle
-    // and now it's come time to put the data on the clipboard.
-    // We always set data, so there isn't a need to actually do anything here.
-    break;
-  case WM_RENDERALLFORMATS:
-    // This message comes when SetClipboardData was sent a null data handle
-    // and now this application is about to quit, so it must put data on
-    // the clipboard before it exits.
-    // We always set data, so there isn't a need to actually do anything here.
-    break;
-  case WM_DRAWCLIPBOARD:
-    break;
-  case WM_DESTROY:
-    break;
-  case WM_CHANGECBCHAIN:
-    break;
-  default:
-    lresult = DefWindowProc(hwnd, message, wparam, lparam);
-    break;
-  }
-  return lresult;
-}
-
 template <typename charT>
 HGLOBAL CreateGlobalData(const std::basic_string<charT>& str) {
   HGLOBAL data =
@@ -161,6 +131,83 @@ void MakeBitmapOpaque(const SkBitmap& bitmap) {
 
 }  // namespace
 
+// Used to create a message-only window handling clipboard-related window
+// messages. It is intended to be passed to OpenClipboard() API.
+class Clipboard::ClipboardWindow
+    : public base::win::MessageWindow::Delegate {
+ public:
+  ClipboardWindow();
+  virtual ~ClipboardWindow();
+
+  // Creates the window if it is not created yat and returns its handle. Returns
+  // NULL if an error occurs.
+  HWND GetHandle();
+
+  // Returns |true| if the window is created.
+  bool IsValid() const;
+
+ private:
+  // base::win::MessageWindow::Delegate interface.
+  virtual bool HandleMessage(HWND hwnd,
+                             UINT message,
+                             WPARAM wparam,
+                             LPARAM lparam,
+                             LRESULT* result) OVERRIDE;
+
+  base::win::MessageWindow window_;
+
+  DISALLOW_COPY_AND_ASSIGN(ClipboardWindow);
+};
+
+
+Clipboard::ClipboardWindow::ClipboardWindow() {
+}
+
+Clipboard::ClipboardWindow::~ClipboardWindow() {
+}
+
+HWND Clipboard::ClipboardWindow::GetHandle() {
+  if (!IsValid())
+    window_.Create(this);
+
+  return window_.hwnd();
+}
+
+bool Clipboard::ClipboardWindow::IsValid() const {
+  return window_.hwnd() != NULL;
+}
+
+bool Clipboard::ClipboardWindow::HandleMessage(HWND hwnd,
+                                               UINT message,
+                                               WPARAM wparam,
+                                               LPARAM lparam,
+                                               LRESULT* result) {
+  switch (message) {
+  case WM_RENDERFORMAT:
+    // This message comes when SetClipboardData was sent a null data handle
+    // and now it's come time to put the data on the clipboard.
+    // We always set data, so there isn't a need to actually do anything here.
+    break;
+  case WM_RENDERALLFORMATS:
+    // This message comes when SetClipboardData was sent a null data handle
+    // and now this application is about to quit, so it must put data on
+    // the clipboard before it exits.
+    // We always set data, so there isn't a need to actually do anything here.
+    break;
+  case WM_DRAWCLIPBOARD:
+    break;
+  case WM_DESTROY:
+    break;
+  case WM_CHANGECBCHAIN:
+    break;
+  default:
+    return false;
+  }
+
+  *result = 0;
+  return true;
+}
+
 Clipboard::FormatType::FormatType() : data_() {}
 
 Clipboard::FormatType::FormatType(UINT native_format) : data_() {
@@ -203,26 +250,12 @@ bool Clipboard::FormatType::operator<(const FormatType& other) const {
   return ToUINT() < other.ToUINT();
 }
 
-Clipboard::Clipboard() : create_window_(false) {
-  if (base::MessageLoop::current()->type() == base::MessageLoop::TYPE_UI) {
-    // Make a dummy HWND to be the clipboard's owner.
-    WNDCLASSEX window_class;
-    base::win::InitializeWindowClass(
-        L"ClipboardOwnerWindowClass",
-        &base::win::WrappedWindowProc<ClipboardOwnerWndProc>,
-        0, 0, 0, NULL, NULL, NULL, NULL, NULL,
-        &window_class);
-    ::RegisterClassEx(&window_class);
-    create_window_ = true;
-  }
-
-  clipboard_owner_ = NULL;
+Clipboard::Clipboard() {
+  if (base::MessageLoop::current()->type() == base::MessageLoop::TYPE_UI)
+    clipboard_owner_.reset(new ClipboardWindow());
 }
 
 Clipboard::~Clipboard() {
-  if (clipboard_owner_)
-    ::DestroyWindow(clipboard_owner_);
-  clipboard_owner_ = NULL;
 }
 
 void Clipboard::WriteObjects(Buffer buffer, const ObjectMap& objects) {
@@ -283,7 +316,7 @@ void Clipboard::WriteBookmark(const char* title_data,
 }
 
 void Clipboard::WriteWebSmartPaste() {
-  DCHECK(clipboard_owner_);
+  DCHECK(clipboard_owner_->IsValid());
   ::SetClipboardData(GetWebKitSmartPasteFormatType().ToUINT(), NULL);
 }
 
@@ -378,7 +411,7 @@ void Clipboard::WriteData(const FormatType& format,
 }
 
 void Clipboard::WriteToClipboard(unsigned int format, HANDLE handle) {
-  DCHECK(clipboard_owner_);
+  DCHECK(clipboard_owner_->IsValid());
   if (handle && !::SetClipboardData(format, handle)) {
     DCHECK(ERROR_CLIPBOARD_NOT_OPEN != GetLastError());
     FreeData(format, handle);
@@ -825,14 +858,7 @@ void Clipboard::FreeData(unsigned int format, HANDLE data) {
 }
 
 HWND Clipboard::GetClipboardWindow() const {
-  if (!clipboard_owner_ && create_window_) {
-    clipboard_owner_ = ::CreateWindow(L"ClipboardOwnerWindowClass",
-                                      L"ClipboardOwnerWindow",
-                                      0, 0, 0, 0, 0,
-                                      HWND_MESSAGE,
-                                      0, 0, 0);
-  }
-  return clipboard_owner_;
+  return clipboard_owner_ ? clipboard_owner_->GetHandle() : NULL;
 }
 
 }  // namespace ui