making widgets invisible

[Thomas Thiele]

No I think this is not sooo nice. Becouse I want to replace the widget
with others.

mode One

|   not changing area           |
--------------------
|   Label    Entry   Button   |
|                                           |
--------------------


and then I want to change the layout into:
mode Two

|   not changing area         |
--------------------
|   Entry   Button  Entry      |
|                                           |
--------------------

(For instance.)
Just like an other dialog but within the mainframe.

And I want to switch between the two modes.