is it possible to have two options for viewing html mail?

[Cameron Simpson]

On 24Oct2020 20:54, Globe Trotter via Mutt-users <mutt-users at mutt.org> wrote:
>Lots of people send me mail in HTML format (even though I do not like it). I have the following set up in my .mailcap:
>
>text/html; w3m -I %{charset} -T text/html; copiousoutput
>
>so it converts things using w3m more or less okay, however, I am wondering is it possible to have an option for viewing using midori/firefox for the cases where w3m is not enough?

Certainly. You have a few choices (not mutually exclusive).

First up, you could bind a keystroke to feed the current message 
to firefox (or whatever browser).

This page on viewing attachments includes a mailcap entry for using 
mozilla if the $DISPLAY environment variable is set:

    https://gitlab.com/muttmua/mutt/-/wikis/MuttFaq/Attachment

You could easily adapt that test to something more manual/on-demand. It 
is written for attachments, so the "%s" in it assumes a filename 
(the attachment).  So does the mailcap entry for displaying messages.

My mailcap entry reads like this:

    text/html; exec 2>&1 && env DISPLAY= unhtml %s; copiousoutput

The primary thing in that line is the display command itself: "unhtml". 
That is a personal script which converts the HTML to text. Write your 
own, however trivial - start (of course) with the line from your 
mailcap.

Importantly, my "unhtml" consults some flags to decide how to do the 
render - you could have yours decide to feed the file to firefox instead 
of (or as well as) w3m. Here's my code:

    https://hg.sr.ht/~cameron-simpson/css/browse/bin/unhtml?rev=tip

It consults some flags to decide what to run - you can see it will use 
w3m or lynx depending on my mood. You could use a similar approach to 
display via firefox depedning on your mood.

As an example, I have:

    set display_filter="mutt-display_filter"

and I use that for rot13 decoding on demand (the on demand being akin to 
your "firefox on demand" wish). So the script is here:

    https://hg.sr.ht/~cameron-simpson/css/browse/bin-cs/mutt-display_filter?rev=tip

and if the MUTT_ROT13 flag is set, it passes the text through tr do 
decode it. Associated with are the following mutt lines:

    set my_toggle_rot13="$my_push_wait_key=no<enter><shell-escape>flag !  MUTT_ROT13 -e flag MUTT_ROT13<enter>$my_pop_wait_key"
    macro index \Cx "$my_toggle_rot13" 'toggle MUTT_ROT13'
    macro pager \Cx "<exit>$my_toggle_rot13<display-message>" 'toggle MUTT_ROT13'

So the ^X keystroke toggles the rot13 mode, which issues a shell command 
to toggle my MUTT_ROT13 flag. If I'm displaying a message (the "pager" 
macro) it exits the pager, toggles the flag, ad reenters the pager.

That might be a starting point.

Cheers,
Cameron Simpson <cs at cskk.id.au>