wxTextCtrl + wxTE_MULTILINE meets wxBoxSizer

But if I simply set wxRE_MULTILINE on
the 1-line sizers, (so that the user could put in extra lines if
they need more space), everything gets deranged. It looks like the
sizer wants to automatically size wxTE_MULTILINE controls to display >> at least 2 lines of text.

The control asusmes that if you ask for multiline that you actually
want multiline. It's just doing what you told it to do.

Yes, but there are 2 different aspects of the problem -- how many
lines show and whether or not the control will accept the enter key,
and it seems a bit regrettable if not grievous that they are linked
as they are. I want one (or two) lines to show, but I want the control
to accept the enter key and contain a multi-line value. Obviously, a
multiline text control can contain more lines of text than it can show,
and can show fewer lines than it contains. But, as I experimented with
this, the sizers started working poorly when the number of lines to
show (based on the sizer proportion) went below about 4.

First of all, if you don't want to display more than one line then it
makes no sense to use wxTE_MULTILINE.

I want to display just 1 line to save screen space in the 95% of cases
when the value is just 1 line. If the user types enter into the
control, he's got multi-line scrollable data, and I'll show him
the multiple lines the next time he displays that multi-line item
on that screen. Of course, no matter how clearly I write this up in
the docs, the users will get baffled by it since only 1 line will show,
so I'll give up on the 1-line wxTextCtrl with wxTE_MULTILINE.
But it would be very nice to be able to get the sizer to work well when
the wxTextCtrl with wxTE_MULTILINE is sized with the sizer proportion
so that it should fit just 2 lines of text.

Al