bookmarks for concept index

[Werner LEMBERG]

The concept index for my groff.texinfo manual, groff.cp, has increased
to 117kByte, covering 16 pages (and it will become longer in the
future).  Navigating with bookmarks to the beginning of the index is
not enough IMHO.  I would like to have this:

(1)

  Concept Index
    A
    B
    C
    ...

or

(2)

  Concept Index
    A-C
    D
    E-I
    ...

or something similar, depending on the number of index entries.  This
is a job only texindex can do.  What about the following:

  . A new command @indexoutlines to activate the feature:

      @indexoutlines cp

    Probably a second argument is useful to control whether (1) or (2)
    or another bookmark scheme shall be used.

    @indexoutlines makes texinfo to emit, say, \doindexoutlines, as
    the first command in the corresponding index file.

  . If texindex sees \doindexoutlines, it counts sorted index
    entries, emitting, say, \initialx, instead of \initial for
    initials which should get a bookmark entry.

For my concept index, I would like to have a single-letter bookmark
entry if the number of index entries with the same starting letter is
larger than 70, say (this is approximately two columns for
@smallbook).  Consequently, for scheme (2) a possible algorithm is to
group index blocks with different starting letters if the entries sum
up to 70 entries, minus the vertical space needed for the initials.
There are some border cases to handle, but I think you get the idea.


    Werner