bug#40213: what-cursor-position could tell the meaning of marks too!

[積丹尼 Dan Jacobson]

It's one of those days. You see those marks "+", "A+" in the Summary
Buffer,

  + 1 200306 16|      |台電資訊處            :RE: Fartsworth Affair
    1 200324 39|      |John (John Lewddis)   :[Maniphest] [Closed] T99999: Can 
not do any thing
 A+ 1 200324 24|      |cclin                 :Re: Ants in pants

but are too lazy to look up what they mean (in (info "(gnus) Other
Marks") etc.).


No worry, C-u C-x = (what-cursor-position) will tell you:

 There are text properties here:
   face                 gnus-summary-high-unread
   gnus-number          31074

Ahhh... alas it could tell you more!

And, on (info "(gnus) Other Marks") it could say "You can also just use
C-u C-x = to figure out what any mark mentioned here means, without
needing to read this page."

P.S., regarding "+", that info page says

   • When using the Gnus agent (*note Agent Basics::), articles may be
     downloaded for unplugged (offline) viewing.  If you are using the
     ‘%O’ spec, these articles get the ‘+’ mark in that spec.  (The
     variable ‘gnus-downloaded-mark’ controls which character to use.)

Well I am not using Gnus agent, and my .gnus.el has no %O or even O in
it. Thus it would be great if what-cursor-position told me what "+" meant.

Gnus v5.13
GNU Emacs 26.3 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.11)
 of 2019-09-23, modified by Debian