bug#47073: 28.0.50; speedbar: sorting in sublists is in reverse

[Eli Zaretskii <eliz@gnu.org>]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Fri, 12 Mar 2021 01:47:38 +0100
> Cc: 47073@debbugs.gnu.org
> 
> haj@posteo.de (Harald Jörg) writes:
> 
> > This isn't specific for "current" Emacs, it happens in Emacs 26.1, too.
> >
> > How to reproduce:
> >
> >  - emacs -Q
> >  - open a Perl file with lots of subroutines
> >    (e.g. https://github.com/foswiki/distro/blob/master/core/lib/Foswiki.pm)
> >    or a Elisp file with lots of defuns
> >    (e.g. lisp/progmodes/cperl-mode.el)
> >  - M-x speedbar
> >
> > Following the default configuration, speedbar clusters the display of
> > subroutines into alphabetically sorted batches of 20 entries each.
> 
> I've barely used speedbar before, but where does speedbar display these
> clusters?  The window that pops up with "emacs -Q" and `M-x speedbar' in
> cperl-mode.el is unclustered, as far as I can tell.

The recipe is incomplete.  Try this:

  . emacs -Q
  . C-x C-f Foswiki.pm
  . M-x speedbar
  . in the speedbar frame go to Foswiki.pm, and click the "+" icon.
  . you should now see the content of cperl.el in batches, sorted
    alphabetically, with each batch having its own "+" icon
  . click on some of the "+" icons of some of the batches and look at
    the order of the entries within

After doing this, I think this observation of the OP:

> While the batches are sorted alphabetically (e.g. "ge to i" comes before
> "l to re" in Foswiki.pm), the entries in each of the batches are sorted
> in reverse: The batch "ge to i" has a first entry of "isValidWikiWord"
> and a last entry of "getApproxRevTime".

is incorrect: the entries are simply unsorted, I guess they appear in
the order they are found in the file or something.  For example, the
entries below "ge to i" in Foswiki.pm are displayed thusly here:

 > isValidWikiWord
 > isValidTopicName
 > isValidWebName
 > isValidEmailAddress
 > i18n
 > inlineAlert
 > isTrue
 > innerExpandMacros
 > inContext
 > generateHTTPHeaders
 > getCGISession
 > getLoginManager
 > getSkin
 > getScriptUrl
 > getPubURL
 > generateRandomChars
 > getWorkArea
 > getApproxRevTime

And you can see that the first 4 are not in any alphabetically-sorted
order.  Likewise, these entries near the end:

 > getCGISession
 > getLoginManager
 > getSkin
 > getScriptUrl
 > getPubURL

aren't sorted, neither in ascending nor in descending order.