Improve handing of the enter key in wxComboBox control

* Copy-paste the code for OnChar in the wxTextCtrl.
* This implements two features:
  1. This adds support for the wxTE_PROCESS_ENTER style.
  2. Support for pressing the default button in a dialog if there is one.

include/wx/osx/combobox.h

@@ -131,6 +131,7 @@ protected:
     virtual void EnableTextChangedEvents(bool enable) wxOVERRIDE;
 
     // callbacks
+    void OnChar(wxKeyEvent& event); // Process 'enter' if required
     void OnKeyDown(wxKeyEvent& event); // Process clipboard shortcuts
 
     // the subcontrols

src/osx/combobox_osx.cpp

@@ -16,11 +16,14 @@
 #include "wx/osx/private.h"
 
 #ifndef WX_PRECOMP
+    #include "wx/button.h"
+    #include "wx/toplevel.h"
 #endif
 
 typedef wxWindowWithItems<wxControl, wxComboBoxBase> RealwxComboBoxBase;
 
 wxBEGIN_EVENT_TABLE(wxComboBox, RealwxComboBoxBase)
+    EVT_CHAR(wxComboBox::OnChar)
     EVT_KEY_DOWN(wxComboBox::OnKeyDown)
 wxEND_EVENT_TABLE()
 
@@ -240,6 +243,52 @@ void wxComboBox::Dismiss()
     GetComboPeer()->Dismiss();
 }
 
+void wxComboBox::OnChar(wxKeyEvent& event)
+{
+    const int key = event.GetKeyCode();
+    bool eat_key = false;
+
+    switch (key)
+    {
+        case WXK_RETURN:
+        case WXK_NUMPAD_ENTER:
+            if (m_windowStyle & wxTE_PROCESS_ENTER)
+            {
+                wxCommandEvent event(wxEVT_TEXT_ENTER, m_windowId);
+                event.SetEventObject(this);
+                event.SetString(GetValue());
+                if (HandleWindowEvent(event))
+                    return;
+            }
+            else
+            {
+                wxTopLevelWindow *tlw = wxDynamicCast(wxGetTopLevelParent(this), wxTopLevelWindow);
+                if (tlw && tlw->GetDefaultItem())
+                {
+                    wxButton *def = wxDynamicCast(tlw->GetDefaultItem(), wxButton);
+                    if (def && def->IsEnabled())
+                    {
+                        wxCommandEvent event(wxEVT_BUTTON, def->GetId());
+                        event.SetEventObject(def);
+                        def->Command(event);
+                        return;
+                    }
+                }
+
+                // this will make wxWidgets eat the ENTER key so that
+                // we actually prevent line wrapping in a single line text control
+                eat_key = true;
+            }
+            break;
+    }
+
+    if (!eat_key)
+    {
+        // perform keystroke handling
+        event.Skip(true);
+    }
+}
+
 void wxComboBox::OnKeyDown(wxKeyEvent& event)
 {
     if (event.GetModifiers() == wxMOD_CONTROL)