Return correct string from wxEVT_TEXT wxComboBox events.

wxCommandEvent::GetString() could return empty string for the
programmatically-generated wxEVT_TEXT events from a wxComboBox.

Fix this by extending the on-demand string retrieval in wxCommandEvent to
wxComboBox as well (it was done only for wxTextCtrl).

Also add a unit test checking that the string has the expected value in the
events sent by all wxTextEntry-derived controls.

Closes #3901.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77057 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/event.cpp

@@ -37,6 +37,7 @@
 
     #if wxUSE_GUI
         #include "wx/window.h"
+        #include "wx/combobox.h"
         #include "wx/control.h"
         #include "wx/dc.h"
         #include "wx/spinbutt.h"
@@ -435,20 +436,27 @@ wxCommandEvent::wxCommandEvent(wxEventType commandType, int theId)
 
 wxString wxCommandEvent::GetString() const
 {
-    if (m_eventType != wxEVT_TEXT || !m_eventObject)
-    {
-        return m_cmdString;
-    }
-    else
+    // This is part of the hack retrieving the event string from the control
+    // itself only when/if it's really needed to avoid copying potentially huge
+    // strings coming from multiline text controls. For consistency we also do
+    // it for combo boxes, even though there are no real performance advantages
+    // in doing this for them.
+    if (m_eventType == wxEVT_TEXT && m_eventObject)
     {
 #if wxUSE_TEXTCTRL
         wxTextCtrl *txt = wxDynamicCast(m_eventObject, wxTextCtrl);
         if ( txt )
             return txt->GetValue();
-        else
 #endif // wxUSE_TEXTCTRL
-            return m_cmdString;
+
+#if wxUSE_COMBOBOX
+        wxComboBox* combo = wxDynamicCast(m_eventObject, wxComboBox);
+        if ( combo )
+            return combo->GetValue();
+#endif // wxUSE_COMBOBOX
     }
+
+    return m_cmdString;
 }
 
 // ----------------------------------------------------------------------------