procedure TForm1.DBGrid1DrawColumnCell(Sender: TObject; const Rect: TRect;
  DataCol: Integer; Column: TColumn; State: TGridDrawState);
begin
  if State = [gdSelected,gdFocused] then begin
    Memo1.Clear;
    Memo1.Lines.Add('Top: '   IntToStr(Rect.Top));
    Memo1.Lines.Add('Left: '   IntToStr(Rect.Left));
    Memo1.Lines.Add('Width: '   IntToStr(Rect.Right - Rect.Left));
    Memo1.Lines.Add('Height: '   IntToStr(Rect.Bottom - Rect.Top));
  end;
end;