Tree Display
============

   If you don't like the normal Gnus summary display, you might try
setting `gnus-use-trees' to `t'.  This will create (by default) an
additional "tree buffer".  You can execute all summary mode commands in
the tree buffer.

   There are a few variables to customize the tree display, of course:

`gnus-tree-mode-hook'
     A hook called in all tree mode buffers.

`gnus-tree-mode-line-format'
     A format string for the mode bar in the tree mode buffers.  The
     default is `Gnus: %%b [%A] %Z'.  For a list of legal specs, 
see Summary Buffer Mode Line..

`gnus-selected-tree-face'
     Face used for highlighting the selected article in the tree
     buffer.  The default is `modeline'.

`gnus-tree-line-format'
     A format string for the tree nodes.  The name is a bit of a
     misnomer, though--it doesn't define a line, but just the node.
     The default value is `%(%[%3,3n%]%)', which displays the first
     three characters of the name of the poster.  It is vital that all
     nodes are of the same length, so you *must* use `%4,4n'-like
     specifiers.

     Legal specs are:

    `n'
          The name of the poster.

    `f'
          The `From' header.

    `N'
          The number of the article.

    `['
          The opening bracket.

    `]'
          The closing bracket.

    `s'
          The subject.

     See Formatting Variables.

     Variables related to the display are:

    `gnus-tree-brackets'
          This is used for differentiating between "real" articles and
          "sparse" articles.  The format is ((REAL-OPEN . REAL-CLOSE)
          (SPARSE-OPEN . SPARSE-CLOSE) (DUMMY-OPEN . DUMMY-CLOSE)), and
          the default is `((?[ . ?]) (?( . ?)) (?{ . ?}))'.

    `gnus-tree-parent-child-edges'
          This is a list that contains the characters used for
          connecting parent nodes to their children.  The default is
          `(?- ?\\ ?|)'.

`gnus-tree-minimize-window'
     If this variable is non-`nil', Gnus will try to keep the tree
     buffer as small as possible to allow more room for the other Gnus
     windows.  If this variable is a number, the tree buffer will never
     be higher than that number.  The default is `t'.

`gnus-generate-tree-function'
     The function that actually generates the thread tree.  Two
     predefined functions are available:
     `gnus-generate-horizontal-tree' and `gnus-generate-vertical-tree'
     (which is the default).

   Here's and example from a horizontal tree buffer:

     {***}-(***)-[odd]-[Gun]
          |     \[Jan]
          |     \[odd]-[Eri]
          |     \(***)-[Eri]
          |           \[odd]-[Paa]
          \[Bjo]
          \[Gun]
          \[Gun]-[Jor]

   Here's the same thread displayed in a vertical tree buffer:

     {***}
       |--------------------------\-----\-----\
     (***)                         [Bjo] [Gun] [Gun]
       |--\-----\-----\                          |
     [odd] [Jan] [odd] (***)                   [Jor]
       |           |     |--\
     [Gun]       [Eri] [Eri] [odd]
                               |
                             [Paa]