A fix for Issue 2673 in chromium: "Flash: IME not available".

To investigate this issue deeply, I noticed this issue consisted of two issues:

1. Windows cannot attach IMEs to a plug-in process.
Somehow, Windows attaches IMEs (i.e. loads IME DLLs, attaches them to a process, and adds message hooks to a window) while creating a top-level window. On the other hand, a plug-in process does not create any top-level windows. These facts prevent Windows from attaching IMEs to windowed plug-ins.

2. The CallWindowProc() function does not dispatch messages to the message-hook functions used by IMEs.
When the |plugin_wnd_proc_| value is a handle referring the DefWindowProc() function, it seems the CallWindowProc() does not dispatch messages to the hook functions used by IMEs.

To fix the former issue, this change once creates a top-level window and have Windows attach IMEs to this window, and change the window to a client window of the given parent window.
To fix the latter issue, this change creates a dummy window procedure WebPluginDelegateImpl::DummyWindowProc(), which just encapsulates the DefWindowProc(), and use it instead of the DefWindowProc() function.

BUG=2673
Review URL: http://codereview.chromium.org/4325
Review URL: http://codereview.chromium.org/4325

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@3391 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 30 insertions, 2 deletions

diff --git a/webkit/glue/plugins/webplugin_delegate_impl.cc b/webkit/glue/plugins/webplugin_delegate_impl.cc
index fa2a64f..e0c74ed 100644
--- a/webkit/glue/plugins/webplugin_delegate_impl.cc
+++ b/webkit/glue/plugins/webplugin_delegate_impl.cc
@@ -369,7 +369,7 @@ bool WebPluginDelegateImpl::WindowedCreatePlugin() {
     WS_EX_LEFT | WS_EX_LTRREADING | WS_EX_RIGHTSCROLLBAR,
     kNativeWindowClassName,
     0,
-    WS_CHILD | WS_CLIPCHILDREN | WS_CLIPSIBLINGS,
+    WS_POPUP | WS_CLIPCHILDREN | WS_CLIPSIBLINGS,
     0,
     0,
     0,
@@ -381,6 +381,21 @@ bool WebPluginDelegateImpl::WindowedCreatePlugin() {
   if (windowed_handle_ == 0)
     return false;
 
+  if (IsWindow(parent_)) {
+    // This is a tricky workaround for Issue 2673 in chromium "Flash: IME not
+    // available". To use IMEs in this window, we have to make Windows attach
+    // IMEs to this window (i.e. load IME DLLs, attach them to this process,
+    // and add their message hooks to this window). Windows attaches IMEs while
+    // this process creates a top-level window. On the other hand, to layout
+    // this window correctly in the given parent window (RenderWidgetHostHWND),
+    // this window should be a child window of the parent window.
+    // To satisfy both of the above conditions, this code once creates a
+    // top-level window and change it to a child window of the parent window.
+    SetWindowLongPtr(windowed_handle_, GWL_STYLE,
+                     WS_CHILD | WS_CLIPCHILDREN | WS_CLIPSIBLINGS);
+    SetParent(windowed_handle_, parent_);
+  }
+
   BOOL result = SetProp(windowed_handle_, kWebPluginDelegateProperty, this);
   DCHECK(result == TRUE) << "SetProp failed, last error = " << GetLastError();
   // Get the name of the plugin, create an atom and set that in a window
@@ -706,7 +721,7 @@ ATOM WebPluginDelegateImpl::RegisterNativeWindowClass() {
   WNDCLASSEX wcex;
   wcex.cbSize         = sizeof(WNDCLASSEX);
   wcex.style          = CS_DBLCLKS;
-  wcex.lpfnWndProc    = DefWindowProc;
+  wcex.lpfnWndProc    = DummyWindowProc;
   wcex.cbClsExtra     = 0;
   wcex.cbWndExtra     = 0;
   wcex.hInstance      = GetModuleHandle(NULL);
@@ -725,6 +740,17 @@ ATOM WebPluginDelegateImpl::RegisterNativeWindowClass() {
   return RegisterClassEx(&wcex);
 }
 
+LRESULT CALLBACK WebPluginDelegateImpl::DummyWindowProc(
+    HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
+  // This is another workaround for Issue 2673 in chromium "Flash: IME not
+  // available". Somehow, the CallWindowProc() function does not dispatch
+  // window messages when its first parameter is a handle representing the
+  // DefWindowProc() function. To avoid this problem, this code creates a
+  // wrapper function which just encapsulates the DefWindowProc() function
+  // and set it as the window procedure of a windowed plug-in.
+  return DefWindowProc(hWnd, message, wParam, lParam);
+}
+
 LRESULT CALLBACK WebPluginDelegateImpl::NativeWndProc(
     HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) {
   WebPluginDelegateImpl* delegate = reinterpret_cast<WebPluginDelegateImpl*>(
diff --git a/webkit/glue/plugins/webplugin_delegate_impl.h b/webkit/glue/plugins/webplugin_delegate_impl.h
index 51d0b9b..f3131f1 100644
--- a/webkit/glue/plugins/webplugin_delegate_impl.h
+++ b/webkit/glue/plugins/webplugin_delegate_impl.h
@@ -132,6 +132,8 @@ class WebPluginDelegateImpl : public WebPluginDelegate {
   ATOM RegisterNativeWindowClass();
 
   // Our WndProc functions.
+  static LRESULT CALLBACK DummyWindowProc(
+      HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
   static LRESULT CALLBACK NativeWndProc(
       HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam);
   static LRESULT CALLBACK FlashWindowlessWndProc(