Implement undo and redo for wxTextCtrl under Mac

Use the parent undo manager to implement these functions.

include/wx/osx/cocoa/private/textimpl.h

@@ -136,12 +136,18 @@ public:
 
     virtual void controlTextDidChange() wxOVERRIDE;
 
+    virtual bool CanUndo() const wxOVERRIDE;
+    virtual void Undo() wxOVERRIDE;
+    virtual bool CanRedo() const wxOVERRIDE;
+    virtual void Redo() wxOVERRIDE;
+
 protected:
     void DoUpdateTextStyle();
 
     NSScrollView* m_scrollView;
     NSTextView* m_textView;
     bool m_useCharWrapping;
+    NSUndoManager* m_undoManager;
 };
 
 class wxNSComboBoxControl : public wxNSTextFieldControl, public wxComboWidgetImpl

src/osx/cocoa/textctrl.mm

@@ -773,6 +773,12 @@ wxNSTextViewControl::wxNSTextViewControl( wxTextCtrl *wxPeer, WXWidget w, long s
 
     [tv setDelegate: tv];
 
+    m_undoManager = nil;
+    if ( wxPeer && wxPeer->GetParent() && wxPeer->GetParent()->GetPeer() && wxPeer->GetParent()->GetPeer()->GetWXWidget() )
+        m_undoManager = [wxPeer->GetParent()->GetPeer()->GetWXWidget() undoManager];
+
+    [tv setAllowsUndo:YES];
+
     InstallEventHandler(tv);
 }
 
@@ -1019,6 +1025,38 @@ void wxNSTextViewControl::controlTextDidChange()
     DoUpdateTextStyle();
 }
 
+bool wxNSTextViewControl::CanUndo() const
+{
+    if ( !m_undoManager )
+        return false;
+
+    return [m_undoManager canUndo];
+}
+
+void wxNSTextViewControl::Undo()
+{
+    if ( !m_undoManager )
+        return;
+
+    [m_undoManager undo];
+}
+
+bool wxNSTextViewControl::CanRedo() const
+{
+    if ( !m_undoManager )
+        return false;
+
+    return [m_undoManager canRedo];
+}
+
+void wxNSTextViewControl::Redo()
+{
+    if ( !m_undoManager )
+        return;
+
+    [m_undoManager redo];
+}
+
 void wxNSTextViewControl::DoUpdateTextStyle()
 {
     if ( m_useCharWrapping )