Antonino,
function MonthCal_SizeRectToMin() seems not to be working at all, in example:
rc := MonthCal_SizeRectToMin( ::hWnd, { 1, 1, 20, 20 } )
XBrowse( rc ) // you get { 1, 1, 20, 20 }
It seems to be working fine this way:
rc := MonthCal_GetMinReqRect( ::hWnd )
XBrowse( rc )