This topic is included for completeness. For more detail see the source code located in the VC\atlmfc\src\mfc folder of your Visual Studio installation.
virtual void OnDrawPopupWindowButtonBorder(
   CDC* pDC,
   CRect rectClient,
   CMFCDesktopAlertWndButton* pButton
);
Parameters
[in] pDC
[in] rectClient
[in] pButton
Requirements
Header: afxvisualmanager.h