Thunderbird's "Edit -> Find -> Search Messages" dialog box has
an unfortunate UI layout problem that can make the dialog very
confusing, and in my case made the feature totally unuseable
until I figured out what the bug was.

I didn't report this earlier, because I couldn't get even one
other person to reproduce it on any version of thunderbird, and
it worked ok for me on new user account, so it was truly puzzling,
however I just finally figured out the cause of the bug.

thunderbird lets you resize the search messages dialog box, which
is an ok thing, however it lets you shrink the dialog too much,
which can cause some of the UI elements to become totally hidden.

In particular, the text entry fields where you would enter your
search criterion vanish completely, and there is no visual indication
that the window is shrunk too far, or that you've done anything
wrong.

Steps to reproduce:
1) Start up thunderbird and click on a mail folder
2) Go to "Edit -> Find -> Search Messages"

at this point you can do one of two things to reproduce the problem
I have experienced:

- Using the window border, shrink the window slowly, and watch
  the text entry fields vanish.  Keep shrinking it, and you'll
  end up with a dialog window that has no text entry fields, and
  there is no obvious indicator to the user that this is due to
  the window being shrunk.

or

- There is a pane divider in the middle of the dialog that you can
  slide up and down to divide the dialog box horizontally.  It is
  directly underneath the buttons "More" and "Fewer", but above
  the "Subject", "Sender", etc. headings that results are placed
  under.  If you even notice that it is there (I never did), you
  can grab it with the mouse and slide it upward until the text
  entry fields are completely hidden, with no visual cue that this
  has happened.


I'm not sure how or when this unfortunate accident happened to
me, but I did not resize the window intentionally, rather one day
when trying to use the search messages feature, all of a sudden,
the dialog text entry boxes were just no longer there.  ;o)

I tried restarting the application like any user would do, and they
never came back.  I was rather baffled, and did not see anything
obvious in the dialog that would suggest the window needed resizing,
or the pane needed moving to make the editable elements visible.

Now that I figured it out, I feel a bit silly, but I've thought
about it, and I believe this is a real dialog bug, because a friendly
UI should never hide elements like this without a way of the user
knowing.

I suspect it is probably a simple issue of just reworking the dialog
box layout to ensure the text entry widgets can never be hidden
when the window is resized or the pane divider is moved.