Add IM and full wxEVT_CHAR support to wxTextCtrl and wxComboBox in wxGTK.

Generate wxEVT_CHAR events for non-ASCII characters entered in these controls
by intercepting their insert-text signal.

Also try to use GtkEntry/GtkTextView internal IM objects but unsuccessfully so
far.

Closes #3158.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73695 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/textentry.h

@@ -50,12 +50,17 @@ public:
 
     // implementation only from now on
     void SendMaxLenEvent();
+    bool GTKEntryOnInsertText(const char* text);
 
 protected:
     // This method must be called from the derived class Create() to connect
     // the handlers for the clipboard (cut/copy/paste) events.
     void GTKConnectClipboardSignals(GtkWidget* entry);
 
+    // And this one to connect "insert-text" signal.
+    void GTKConnectInsertTextSignal(GtkEntry* entry);
+
+
     virtual void DoSetValue(const wxString& value, int flags);
     virtual wxString DoGetValue() const;
 
@@ -65,6 +70,9 @@ protected:
 
     virtual bool DoAutoCompleteStrings(const wxArrayString& choices);
 
+    // Override the base class method to use GtkEntry IM context.
+    virtual int GTKIMFilterKeypress(GdkEventKey* event) const;
+
 private:
     // implement this to return the associated GtkEntry or another widget
     // implementing GtkEditable