Refactor wxGTK IM-related code to allow future modifications.

No real changes, just make it possible to use a different IM than the one
allocated in wxWindow for input handling. This will be used in the upcoming
changes to wxTextEntry and the related classes.

See #3158.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73693 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/window.h

@@ -24,6 +24,9 @@
 // some additional data needed for key events processing
 struct wxGtkIMData;
 
+typedef struct _GdkEventKey GdkEventKey;
+typedef struct _GtkIMContext GtkIMContext;
+
 WX_DEFINE_EXPORTED_ARRAY_PTR(GdkWindow *, wxArrayGdkWindows);
 
 extern "C"
@@ -272,7 +275,28 @@ public:
     void GTKDisableFocusOutEvent();
     void GTKEnableFocusOutEvent();
 
-    wxGtkIMData         *m_imData;
+
+    // Input method support
+
+    // The IM context used for generic, i.e. non-native, windows.
+    //
+    // It might be a good idea to avoid allocating it unless key events from
+    // this window are really needed but currently we do it unconditionally.
+    //
+    // For native widgets (i.e. those for which IsOfStandardClass() returns
+    // true) it is NULL.
+    GtkIMContext* m_imContext;
+
+    // Pointer to the event being currently processed by the IME or NULL if not
+    // inside key handling.
+    GdkEventKey* m_imKeyEvent;
+
+    // This method generalizes gtk_im_context_filter_keypress(): for the
+    // generic windows it does just that but it's overridden by the classes
+    // wrapping native widgets that use IM themselves and so provide specific
+    // methods for accessing it such gtk_entry_im_context_filter_keypress().
+    virtual int GTKIMFilterKeypress(GdkEventKey* event) const;
+
 
     // indices for the arrays below
     enum ScrollDir { ScrollDir_Horz, ScrollDir_Vert, ScrollDir_Max };