Hi Malcolm, Emanuel, Andreas, and Adam,

Thank you for your replies!  

Malcolm Purvis <malcolm@purvis.id.au> writes:

> I use the following settings, which displays the text part of the
> message whenever possible, but leaves a button that will display the
> HTML if I want:
>
> (setq
>   gnus-buttonized-mime-types '("multipart/alternative" "multipart/signed")
>    mm-discouraged-alternatives '("text/html" "image/.*")
>    gnus-mime-display-multipart-related-as-mixed t
> )

Emanuel Berg <moasen@zoho.com> writes:

> This is what I have: [1]
>
> ;;; HTML and NON-ASCII
> (setq gnus-inhibit-images t)
> (setq mm-discouraged-alternatives '("text/html" "text/richtext"))
> (setq mm-text-html-renderer 'w3m)
> ;; (setq mm-automatic-display
> ;;       (cl-remove-if (remove "text/html" mm-automatic-display))

Adam Sjøgren <asjo@koldfront.dk> writes:

> Instead of mm-inline-override-types I have this:
>
>   (setq mm-automatic-display (remove "text/html" mm-automatic-display))

Unfortunately, I couldn't get these various methods to work, even though
I did try fiddling with them in various ways like suggested above.  In
the end, the only way I found to work around it was to tell Gnus to
ignore HTML entirely, which is OK but a bit heavy-handed.

Andreas Schwab <schwab@linux-m68k.org> writes:

> I'm using these settings:
>
> (setq mm-discouraged-alternatives '("text/html" "text/richtext" "text/enriched"
> 				    "multipart/related" "multipart/mixed"))
> (setq mm-inline-override-types '("application/octet-stream" "text/html"))

This may actually be what I want!  Using mm-inline-override-types like
this seems to suppress the automatic display of HTML, and it also leaves
a button for me to interact with.  Excellent!

This allows me to view the HTML in an external browser by typing "K H"
(gnus-article-browse-html-article), which is quite nice.  However, when
I type RET (gnus-article-press-button), it displays the HTML in-line,
instead of rendering it.  This leads me to three more questions:

* Is mm-inline-override-types supposed to be used like this?  It doesn't
  seem to be mentioned in the manual, so I'm a little concerned it might
  be private or something.

* Is it possible to coax Gnus into displaying the HTML part in-line when
  I invoke gnus-article-press-button, even though I've set
  mm-inline-override-types to treat text/html as an attachment?

* Why might it be that when I invoke gnus-article-browse-html-article,
  the article is opened externally using IceCat rather than internally
  using shm?  The value of mm-text-html-renderer is shr, so I expected
  Gnus to open the HTML part using shr.  I was surprised that it used
  IceCat, but it isn't a big deal, I suppose.

Thank you for all your advice!  It's been very helpful.

-- 
Chris