[Newbie] Controlling size of containers?

[Olivier <Olivier Ramare univ-lille1 fr>]

Dear all,

  Since I'm here: thanks to the very valuable answers I got till now!
  Then:
    -- I'm not so learned in understanding the size taken by containers.
    -- What I would like is
           -- to create a fantom widget: in a table, I need to fill one
              element at beginning and the others later, but I want
              my container (table) to already take the size of three
              elements like my first one.
           -- to impose the width and length of a GTK_TEXT_VIEW:
              my trials to this effect got me exactly... nowhere!
  Many thanks in advance,
  Best,
  Amities,
           Olivier