Throughout this manual you’ve probably noticed lots of variables called
things like gnus-group-line-format and
gnus-summary-mode-line-format. These control how Gnus is to
output lines in the various buffers. There’s quite a lot of them.
Fortunately, they all use the same syntax, so there’s not that much to
be annoyed by.
Gnus does not use the font locking machinery used by most modes in
Emacs, so switching font-lock-mode on in the Gnus
group/summary/article buffers usually doesn’t do anything
useful—instead it’ll just mess up the faces that Gnus has already
put in the buffer. (This is also the case for other minor modes that
use the font locking machinery, like whitespace-mode.)
Here’s an example format spec (from the group buffer): ‘%M%S%5y: %(%g%)\n’. We see that it is indeed extremely ugly, and that there are lots of percentages everywhere.
Currently Gnus uses the following formatting variables:
gnus-group-line-format, gnus-summary-line-format,
gnus-server-line-format, gnus-topic-line-format,
gnus-group-mode-line-format,
gnus-summary-mode-line-format,
gnus-article-mode-line-format,
gnus-server-mode-line-format, and
gnus-summary-pick-line-format.
All these format variables can also be arbitrary elisp forms. In that
case, they will be evaled to insert the required lines.
Gnus includes a command to help you while creating your own format
specs. M-x gnus-update-format will eval the current form,
update the spec in question and pop you to a buffer where you can
examine the resulting Lisp code to be run to generate the line.