#34 Add drop-down with menu-properties

[Christer Sandberg]

When selecting a certain value (each corrspondning to
some text) one can use a drop-down. One can fairly
simple use a "single-menu" for similar purposes (which
is specially useful in case the selection does not map
directly to consecutive numbers or the selections are
hierarchically organized). The problem here is that the
text-label of the single-menu is a constant text. When
using it in the described context, one expects the
selected value to be reflected as the label of
"single-menu". It is of course possible to do this, but
it requires quite a lot of ugly wor-arounds (e.g.
remove the single-menu and then re-create it, which in
turn requires a a container to be created for the
single-menu only, making some assumptions about
spacing-sizes that is under cgui's control).
Maybe a solution does not require a new widget type,
maybe it would be sufficient to be able to tell the
maximum length of all potential labels for the single
menu, and then re-set the label.