Tree problems

["David Z. Maze" <dmaze donut mit edu>]

I've written a gtk app that, given a list of usernames, checks which
of them are logged in.  The usernames can be sorted into categories,
and each category can optionally belong to a single parent category.

To display this, I use a GtkTree widget.  My main window is a vbox
with a menubar, the tree, and a "Update" button.  Pressing the button
forces a check on which users are logged in.  If they have logged in
since the last update, their name is added to the tree.  If they have
logged out, their name is deleted.

Problems I've run into (on 0.99.3 up to 0.99.7):

-- The "+" and "-" pixmaps don't display correctly when the user
   expands/collapses tree branches.  It looks like the new pixmaps are 
   displayed with their centers at the upper-left corner of the
   original pixmaps.  In 0.99.7, the old pixmap is visible underneath; 
   in older versions, it was erased first.

-- Adding and removing elements from the tree fails to cause the right 
   thing to be drawn.  A tree branch might look like this:

      Title                     Title
       +-A                       +-A
       +-B   ==>  Add "D"   ==>  +-B
       L-C                       L-C  <== (should have "T" piece, not corner)
                                 L-D

      Title                     Title
       +-A                       +-A
       +-B   ==> Remove "C" ==>  +-B <== (should have corner piece, not "T")
       L-C

-- 
 _____________________________
/                             \  "The cat's been in the box for over
|          David Maze         |  20 years.  Nobody's feeding it.  The
|         dmaze@mit.edu       |            cat is dead."
| http://donut.mit.edu/dmaze/ |  -- Grant, on Schroedinger's Cat
\_____________________________/