bug#64301: 30.0.50; ERC 5.6: Make speaker labels easier to work with

[J.P.]

Tags: patch

Currently, modules that operate on inserted messages use heuristics,
like delimiting characters and face properties, to find the bounds of
the "speaker label" (my term for the stylized nick prepended to the
start of every displayed message). I think it's worth making these
boundaries easier and more reliable to detect. At a bare minimum, having
a specific text property or field spanning the nick portion should
provide enough information to identify other regions of interest
preceding the actual message (in most cases). The attached patch
attempts to do this.

However, it may be useful in the long run to provide an internal
interface for influencing how this happens. Use cases include hiding or
altering bookend styling (currently hard-coded to angle brackets) and
using alternate display names for nicks themselves. One approach for
implementing something like this was proposed in an iteration of the
change set from bug#60933 [1] but was ultimately removed prior to
installation.

The attached patch also fixes a somewhat related bug discovered by
incal. From emacs -Q:

  - Set `erc-format-nick-function' to `erc-format-@nick'
  - Customize `erc-nick-prefix-face' to make it easily noticeable
  - Connect to some network
  - Create a new dummy channel and say something
  - Notice that your speaker nick is decorated with the status prefix
    "@" but that it lacks the face changes you made earlier

The only thing giving me pause about this bug is that there's no
(surviving) mention of it in the usual places, and the offending code
has been around since at least 2006. So, it's possible we're still
missing something here.

Thanks.

[1] https://lists.gnu.org/archive/html/emacs-erc/2023-04/msg00018.html
    See `erc--format-speaker-functions' in the third patch
    0003-5.6-Use-getter-for-finding-users-in-erc-server-PRIVM.patch.


In GNU Emacs 30.0.50 (build 4, x86_64-pc-linux-gnu, GTK+ Version
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Repository revision: a6de0d22e4209e2c75dbf1e8c005dfc9d8c64cce
Repository branch: master
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0001-5.6-Don-t-clobber-erc-nick-prefix-face.patch
Description: Text Data