override MSWGetDefaultBgBrush() to use transparent brush

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@30970 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/checkbox.h

@@ -50,9 +50,9 @@ public:
 
 protected:
     virtual wxSize DoGetBestSize() const;
+    virtual WXHBRUSH MSWGetDefaultBgBrush();
 
     virtual void DoSet3StateValue(wxCheckBoxState value);
-
     virtual wxCheckBoxState DoGet3StateValue() const;
 
 private:

src/msw/checkbox.cpp

@@ -201,6 +201,11 @@ wxSize wxCheckBox::DoGetBestSize() const
     return wxSize(wCheckbox, hCheckbox);
 }
 
+WXHBRUSH wxCheckBox::MSWGetDefaultBgBrush()
+{
+    return ::GetStockObject(NULL_BRUSH);
+}
+
 void wxCheckBox::SetValue(bool val)
 {
     if (val)