GDK W32: Test for IME correctly

ImmIsIME() doesn't work (always returns TRUE) since Vista.
Use ITfActiveLanguageProfileNotifySink to detect TSF changes,
which are equal to IME changes for us.

Also make sure that IMMultiContext re-loads the IM when keyboard layout
changes, otherwise there's a subtle bug that could happen:
* Run GTK application with non-IME layout (US, for example)
* Focus on an editable widget (GtkEntry, for example)
* IM Context is initialized to use the simple IM
* Switch to an IME layout (such as Korean)
* Start typing
* Since IME module is not loaded yet, keypresses are handled
  by a default MS IME handler
* Once IME commits a character, GDK will get a WM_KEYDOWN,
  which will trigger a GdkKeyEvent, which will be handled by
  an event filter in IM Context, which will finally re-evaluate
  its status and load IME, and only after that GTK will get
  to handle IME by itself - but by that point input would
  already be broken.
To avoid this we can emit a dummy event (with Void keyval),
which will cause IM Context to load the appropriate module
immediately.

gdk/win32/gdkdisplay-win32.c

@@ -38,6 +38,8 @@
 
 #include <dwmapi.h>
 
+#include "gdkwin32langnotification.h"
+
 static int debug_indent = 0;
 
 /**
@@ -536,6 +538,7 @@ _gdk_win32_display_open (const gchar *display_name)
                                       NULL);
   _gdk_device_manager->display = _gdk_display;
 
+  _gdk_win32_lang_notification_init ();
   _gdk_drag_init ();
   _gdk_drop_init ();
 
@@ -701,6 +704,7 @@ gdk_win32_display_finalize (GObject *object)
 
   _gdk_win32_display_finalize_cursors (display_win32);
   _gdk_win32_dnd_exit ();
+  _gdk_win32_lang_notification_exit ();
 
   g_ptr_array_free (display_win32->monitors, TRUE);
 

gdk/win32/gdkevents-win32.c

@@ -2113,7 +2113,6 @@ gdk_event_translate (MSG  *msg,
     case WM_INPUTLANGCHANGE:
       _gdk_input_locale = (HKL) msg->lParam;
       _gdk_win32_keymap_set_active_layout (GDK_WIN32_KEYMAP (_gdk_win32_display_get_keymap (_gdk_display)), _gdk_input_locale);
-      _gdk_input_locale_is_ime = ImmIsIME (_gdk_input_locale);
       GetLocaleInfo (MAKELCID (LOWORD (_gdk_input_locale), SORT_DEFAULT),
 		     LOCALE_IDEFAULTANSICODEPAGE,
 		     buf, sizeof (buf));
@@ -2125,6 +2124,20 @@ gdk_event_translate (MSG  *msg,
 			 (gpointer) msg->lParam, _gdk_input_locale_is_ime ? " (IME)" : "",
 			 _gdk_input_codepage));
       gdk_display_setting_changed (display, "gtk-im-module");
+
+      /* Generate a dummy key event to "nudge" IMContext */
+      event = gdk_event_new (GDK_KEY_PRESS);
+      event->any.surface = window;
+      event->key.time = _gdk_win32_get_next_tick (msg->time);
+      event->key.keyval = GDK_KEY_VoidSymbol;
+      event->key.hardware_keycode = 0;
+      event->key.group = 0;
+      gdk_event_set_scancode (event, 0);
+      gdk_event_set_device (event, device_manager_win32->core_keyboard);
+      gdk_event_set_source_device (event, device_manager_win32->system_keyboard);
+      event->key.is_modifier = FALSE;
+      event->key.state = 0;
+      _gdk_win32_append_event (event);
       break;
 
     case WM_SYSKEYUP:

gdk/win32/gdkglobals-win32.c

@@ -39,7 +39,7 @@ HINSTANCE	  _gdk_app_hmodule;
 gint		  _gdk_input_ignore_core;
 
 HKL		  _gdk_input_locale;
-gboolean	  _gdk_input_locale_is_ime;
+gboolean	  _gdk_input_locale_is_ime = FALSE;
 UINT		  _gdk_input_codepage;
 
 gint		  _gdk_input_ignore_wintab = FALSE;

gdk/win32/gdkmain-win32.c

@@ -83,7 +83,6 @@ _gdk_win32_surfaceing_init (void)
   _gdk_display_hdc = CreateDC ("DISPLAY", NULL, NULL, NULL);
   _gdk_input_locale = GetKeyboardLayout (0);
   _gdk_win32_keymap_set_active_layout (GDK_WIN32_KEYMAP (_gdk_win32_display_get_keymap (_gdk_display)), _gdk_input_locale);
-  _gdk_input_locale_is_ime = ImmIsIME (_gdk_input_locale);
   GetLocaleInfo (MAKELCID (LOWORD (_gdk_input_locale), SORT_DEFAULT),
 		 LOCALE_IDEFAULTANSICODEPAGE,
 		 buf, sizeof (buf));

gdk/win32/gdkwin32langnotification.c

@@ -0,0 +1,172 @@
+/* GDK - The GIMP Drawing Kit
+ * Copyright (C) 2019 Руслан Ижбулатов <lrn1986@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#define COBJMACROS
+#include <msctf.h>
+
+#include <gdk/gdk.h>
+
+#include "gdkprivate-win32.h"
+
+struct _GdkWin32ALPNSink
+{
+  ITfActiveLanguageProfileNotifySink itf_alpn_sink;
+
+  gint ref_count;
+};
+
+typedef struct _GdkWin32ALPNSink GdkWin32ALPNSink;
+
+static GdkWin32ALPNSink *actlangchangenotify = NULL;
+static ITfSource *itf_source = NULL;
+static DWORD actlangchangenotify_id = 0;
+
+static ULONG STDMETHODCALLTYPE
+alpn_sink_addref (ITfActiveLanguageProfileNotifySink *This)
+{
+  GdkWin32ALPNSink *alpn_sink = (GdkWin32ALPNSink *) This;
+  int ref_count = ++alpn_sink->ref_count;
+
+  return ref_count;
+}
+
+static HRESULT STDMETHODCALLTYPE
+alpn_sink_queryinterface (ITfActiveLanguageProfileNotifySink *This,
+                          REFIID                              riid,
+                          LPVOID                             *ppvObject)
+{
+  *ppvObject = NULL;
+
+  if (IsEqualGUID (riid, &IID_IUnknown))
+    {
+      ITfActiveLanguageProfileNotifySink_AddRef (This);
+      *ppvObject = This;
+      return S_OK;
+    }
+
+  if (IsEqualGUID (riid, &IID_ITfActiveLanguageProfileNotifySink))
+    {
+      ITfActiveLanguageProfileNotifySink_AddRef (This);
+      *ppvObject = This;
+      return S_OK;
+    }
+
+  return E_NOINTERFACE;
+}
+
+static ULONG STDMETHODCALLTYPE
+alpn_sink_release (ITfActiveLanguageProfileNotifySink *This)
+{
+  GdkWin32ALPNSink *alpn_sink = (GdkWin32ALPNSink *) This;
+  int ref_count = --alpn_sink->ref_count;
+
+  if (ref_count == 0)
+    {
+      g_free (This);
+    }
+
+  return ref_count;
+}
+
+static HRESULT STDMETHODCALLTYPE
+alpn_sink_on_activated (ITfActiveLanguageProfileNotifySink *This,
+                        REFCLSID                            clsid,
+                        REFGUID                             guidProfile,
+                        BOOL                                fActivated)
+{
+  _gdk_input_locale_is_ime = fActivated;
+  return S_OK;
+}
+
+static ITfActiveLanguageProfileNotifySinkVtbl alpn_sink_vtbl = {
+  alpn_sink_queryinterface,
+  alpn_sink_addref,
+  alpn_sink_release,
+  alpn_sink_on_activated,
+};
+
+static GdkWin32ALPNSink *
+alpn_sink_new ()
+{
+  GdkWin32ALPNSink *result;
+
+  result = g_new0 (GdkWin32ALPNSink, 1);
+  result->itf_alpn_sink.lpVtbl = &alpn_sink_vtbl;
+  result->ref_count = 0;
+
+  ITfActiveLanguageProfileNotifySink_AddRef (&result->itf_alpn_sink);
+
+  return result;
+}
+
+
+void
+_gdk_win32_lang_notification_init ()
+{
+  HRESULT hr;
+  ITfThreadMgr *itf_threadmgr;
+
+  CoInitializeEx (NULL, COINIT_APARTMENTTHREADED);
+
+  if (actlangchangenotify != NULL)
+    return;
+
+  hr = CoCreateInstance (&CLSID_TF_ThreadMgr,
+                         NULL,
+                         CLSCTX_INPROC_SERVER,
+                         &IID_ITfThreadMgr,
+                         (LPVOID *) &itf_threadmgr);
+
+  if (!SUCCEEDED (hr))
+    return;
+
+  hr = ITfThreadMgr_QueryInterface (itf_threadmgr, &IID_ITfSource, (VOID **) &itf_source);
+  ITfThreadMgr_Release (itf_threadmgr);
+
+  if (!SUCCEEDED (hr))
+    return;
+
+  actlangchangenotify = alpn_sink_new ();
+
+  hr = ITfSource_AdviseSink (itf_source,
+                             &IID_ITfActiveLanguageProfileNotifySink,
+                             (IUnknown *) actlangchangenotify,
+                             &actlangchangenotify_id);
+
+  if (!SUCCEEDED (hr))
+    {
+      ITfActiveLanguageProfileNotifySink_Release (&actlangchangenotify->itf_alpn_sink);
+      actlangchangenotify = NULL;
+      ITfSource_Release (itf_source);
+      itf_source = NULL;
+    }
+}
+
+void
+_gdk_win32_lang_notification_exit ()
+{
+  if (actlangchangenotify != NULL && itf_source != NULL)
+    {
+      ITfSource_UnadviseSink (itf_source, actlangchangenotify_id);
+      ITfSource_Release (itf_source);
+      ITfActiveLanguageProfileNotifySink_Release (&actlangchangenotify->itf_alpn_sink);
+    }
+
+  CoUninitialize ();
+}

gdk/win32/gdkwin32langnotification.h

@@ -0,0 +1,26 @@
+/*
+ * gdkwin32langnotification.h
+ *
+ * Copyright 2019 Руслан Ижбулатов <lrn1986@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GDK_WIN32_LANGNOTIFICATION_H__
+#define __GDK_WIN32_LANGNOTIFICATION_H__
+
+void _gdk_win32_lang_notification_init (void);
+void _gdk_win32_lang_notification_exit (void);
+
+#endif

gdk/win32/meson.build

@@ -17,6 +17,7 @@ gdk_win32_sources = files([
   'gdkglobals-win32.c',
   'gdkhdataoutputstream-win32.c',
   'gdkkeys-win32.c',
+  'gdkwin32langnotification.c',
   'gdkmain-win32.c',
   'gdkmonitor-win32.c',
   'gdkproperty-win32.c',