[WinAPI] Ograniczanie rysowania

PAINTSTRUCT ps;
HDC hdc = BeginPaint( hwnd, & ps );
HPEN hpen = CreatePen( PS_SOLID, 1, 0x0000FF );
HPEN oldpen =( HPEN ) SelectObject( hdc, hpen );
POINT oldpoint;
MoveToEx( hdc, 100, 100, & oldpoint );
LineTo( hdc, 280, 20 );
LineTo( hdc, 100, 40 );
SelectObject( hdc, oldpen );
DeleteObject( hpen );
EndPaint( hwnd, & ps );

bool CDraw::setClipRect( const CRect & rect )
{
    bool bResult = true;
    HRGN hrgn =::CreateRectRgn( rect.left, rect.top, rect.right + 1, rect.bottom + 1 );
    if(::SelectClipRgn( m_hdc, hrgn ) == ERROR )
         bResult = false;
   
    ::DeleteObject( hrgn );
    return bResult;
}