Finding Overlapped windows areas

[ovidiucucu]

This is just a sample.
This function returns the screen coordinates of the
Calculator's area covered by Registry Editor.
You can enhance it by passing windows names or/and
classes names, and convert to the client coordinates.

BOOL GetRegistryOverCalculatorRect( RECT &rcOver )
{
   BOOL bRet = FALSE;
   ::ZeroMemory( &rcOver, sizeof( RECT ) );

   // Search the "Registry Editor" window
   HWND hWndReg  = ::FindWindow( NULL, _T("Registry Editor") );
   if( NULL == hWndReg )
   {
      // Registry Editor not found
      return bRet; 
   }

   // Now search the Calculator window 
   // begining with the next window in the Z order, 
   // after the Registry Editor 
   HWND hWndCalc = ::FindWindowEx( NULL, 
                                   hWndReg, 
                                   NULL, 
                                   _T("Calculator") );
   
   if( NULL == hWndCalc )
   {
      // "Calculator" not found 
      // or it is not under "Registry Editor"
      return bRet; 
   }

   RECT rcCalc, rcReg;
   ::GetWindowRect( hWndCalc, &rcCalc );
   ::GetWindowRect( hWndReg, &rcReg );

   bRet = ::IntersectRect( &rcOver, &rcCalc, &rcReg ); 

   return bRet; // returns FALSE if "Registry Editor"
                // is not over "Calculator"

}

Enjoy!