Ограничить подвижность формы

For some reason messages.pas declares no message record for this message

type
  TWmMoving = record
    Msg: Cardinal;
    fwSide: Cardinal;
    lpRect: PRect;
    Result: Integer;
  end;
 
// Add a handler to your forms private section:
 
procedure WMMoving(var msg: TWMMoving); message WM_MOVING;
 
// Implement it as
 
  procedure TFormX.WMMoving(var msg: TWMMoving);
  var
    r: TRect;
  begin
    r := Screen.WorkareaRect;
   // compare the new form bounds in msg.lpRect^ with r and modify it if
   // necessary
    if msg.lprect^.left < r.left then
      OffsetRect(msg.lprect^, r.left - msg.lprect^.left, 0);
    if msg.lprect^.top < r.top then
      OffsetRect(msg.lprect^, 0, r.top - msg.lprect^.top);
    if msg.lprect^.right > r.right then
      OffsetRect(msg.lprect^, r.right - msg.lprect^.right, 0);
    if msg.lprect^.bottom > r.bottom then
      OffsetRect(msg.lprect^, 0, r.bottom - msg.lprect^.bottom);
    inherited;
  end;

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