[bug #64396] vim tip for using editor as manual pager frustrated by groff 1.23.0 change

[G. Branden Robinson]

Update of bug #64396 (project groff):

                Category:                    None => Driver grotty          
                  Status:                    None => Invalid                
             Assigned to:                    None => gbranden               
             Open/Closed:                    Open => Closed                 
                 Summary: [BUG/REGRESSION] weird charachters using vim as
manpage => vim tip for using editor as manual pager frustrated by groff 1.23.0
change

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Follow-up Comment #1:

Hi alio,

[comment #0 original submission:]

> export PAGER='/bin/bash -c "vim -MRn -c \"set buftype=nofile showtabline=0
ft=man ts=8 nomod nolist norelativenumber nonu noma\" -c \"normal L\" -c
\"nmap q :qa<CR>\"</dev/tty <(col -b)"'
> 
> export VISUAL='vim'
> 
> Until version 1.22.4 everything worked ok
> 
> With version 1.23.0 , manpages are showed with weird 1m and 0m at the
beginning and at the end of each line
> 
> Example on man groff
[...]
> With version 1.22.4 , everything works ok

I can reproduce this even with groff 1.22.4...


man man


...if I revert or comment out the patch that Debian's groff package on my
system uses.

/etc/groff/man.local:

.  \" Debian: Disable the use of SGR (ANSI colour) escape sequences by
.  \" grotty.
.  \" commented (SGR re-enabled) by Branden, 2019-06-16 --GBR
.  \" if '\V[GROFF_SGR]'' \
.  \" output x X tty: sgr 0


With both (Debian's) groff 1.22.4 and a stock groff 1.23.0 install, the
following restores the behavior I think you're looking for.


$ GROFF_NO_SGR=1 man man


> I don't know if other user-cases are affected and what this bug technically
means

The technical explanation is in groff 1.23.0's NEWS file.


o The "sgr" device control command, which dynamically configured support
  for ISO 6429/ECMA-48 SGR escape sequences (and restored traditional
  overstriking behavior if disabled), has been removed.  It took effect
  only at page boundaries.  grotty's "-c" command-line option and the
  GROFF_NO_SGR environment variable remain supported.


One of the things you give up with this approach is the new support for
hyperlinks in groff output to terminals, including hyperlink support in man
pages.

Also from NEWS:


o The an (man) macro package can now produce clickable hyperlinks within
  terminal emulators, using the OSC 8 support added to grotty(1) (see
  below).  The groff man(7) extension macros `UR` and `MT`, present
  since 2007, expose this feature.  At present the feature is disabled
  by default in `man.local` pending more widespread recognition of OSC 8
  sequences in pager programs.  The package now recognizes a `U`
  register to enable hyperlinks in any output driver supporting them.

  Use a command like
    printf '\033]8;;man:grotty(1)\033\\grotty(1)\033]8;;\033\\\n' | more
  to check your terminal and pager for OSC 8 support.  If you see
  "grotty(1)" and no additional garbage characters, then you may wish to
  edit "man.local" to remove the lines that disable this feature.

o The an (man) macro package supports a new macro, `MR`, intended for
  use by man page cross references in preference to the font style
  alternation macros historically used.  Where before you would write
    .BR ls (1).
  or
    .IR ls (1).
  you should now write
    .MR ls 1 .
  (the third argument, typically used for trailing punctuation, is
  optional).  Because the macro semantically identifies a man page, it
  can create a clickable hyperlink ("man:ls(1)" for the above example)
  on supporting devices.  Furthermore, a new string, `MF`, defines the
  font to be used for setting the man page topic (the first argument to
  `MR` and `TH`), permitting configuration by distributions, sites, and
  users.

  Inclusion of the `MR` macro was prompted by its introduction to
  Plan 9 from User Space's troff in August 2020.  Its purpose is to
  ameliorate several long-standing problems with man page cross
  references: (1) the package's lack of inherent hyperlink support for
  them; (2) false-positive identification of strings resembling man page
  cross references (as can happen with "exit(1)", "while(1)",
  "sleep(5)", "time(0)" and others) by terminal emulators and other
  programs; (3) the unwanted intrusion of hyphens into man page topics,
  which frustrates copy-and-paste operations (this problem has always
  been avoidable through use of the \% escape sequence, but cross
  references are frequent in man pages and some page authors are
  inexpert *roff users); and (4) deep divisions in man page maintenance
  communities over which typeface should be used to set the man page
  topic (italics, roman, or bold).


I don't know if Vim supports hyperlinks in editor buffers (and I say that even
being a Vim user).  If it does, then the Vim tips community will probably want
to come up with some Vimscript to interpret SGR and OSC escape sequences (from
ISO 6429/ECMA-48), so that it can support the full set of groff man(7)
features when operating as a man pager.


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