icon_xmargin                       |
        /                    icon_xmargin   | == il_col_width
       /   il_icon_size    /                |
    +-*-+---------------+-*-+
    |   |               |   |
    |   |               |   |
    |   |               |   |
    |   |               |   |
    |   |     icon      |   |  il_icon_size
    |   |               |   |
    |   |               |   |
    |   |               |   |
    +---+---------------+---+
    |                       |  1/2 LABEL_YMARGIN
    +-----------------------+
    |     label, line 1     |
    |     label, line 2     |  il_label_height = 2 lines
    +-----------------------+
    |                       |  1/2 LABEL_YMARGIN
    +-----------------------+
                               ---------------------
                            == il_row_height



                                viewport (4 px ?)
                               /
  +---------------------------++-+
  | margin: 5 px              ||^| scrollbar (automatic) (15 px ?)
  +----------+----------+-----|| |
  |          |          |     || |
  |   icon   |   icon   |     || |
  |          |          |     || |
  |          |          |     || |
  +----------+----------+     || |
  |          |          |     || |
  |   icon   |   icon   |     || |
  |          |          |     || |
  |          |          |     || |
  +----------+----------+     || |
  |          |          |     || |
  |   icon   |   icon   |     ||v|
  +---------------------------++-+