Don't crash in wxWindowMac::OSXSimulateFocusEvents().

The code didn't properly account for the possibility of wxEVT_KILL_FOCUS
handler deleting the focused window (as happens e.g. in wxListCtrl inline edit
controls). E.g. rapidly clicking wxEditableListBox buttons could trigger a
crash here when sending wxEVT_SET_FOCUS to an already-deleted window.

Use wxWeakRef<> to check if the window is still alive.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75199 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/window_osx.cpp

@@ -39,6 +39,7 @@
 #include "wx/tooltip.h"
 #include "wx/spinctrl.h"
 #include "wx/geometry.h"
+#include "wx/weakref.h"
 
 #if wxUSE_LISTCTRL
     #include "wx/listctrl.h"
@@ -610,7 +611,7 @@ void wxWindowMac::SetFocus()
 
 void wxWindowMac::OSXSimulateFocusEvents()
 {
-    wxWindow* former = FindFocus() ;
+    wxWeakRef<wxWindow> former = FindFocus() ;
     if ( former != NULL && former != this )
     {
         {
@@ -620,6 +621,9 @@ void wxWindowMac::OSXSimulateFocusEvents()
             former->HandleWindowEvent(event) ;
         }
 
+        // 'former' could have been destroyed by a wxEVT_KILL_FOCUS handler,
+        // so we must test it for non-NULL again
+        if ( former )
         {
             wxFocusEvent event(wxEVT_SET_FOCUS, former->GetId());
             event.SetEventObject(former);