9.4.2 Mode Line Formatting
Mode line formatting variables (e.g.,
gnus-summary-mode-line-format) follow the same rules as other,
buffer line oriented formatting variables (see Formatting Basics)
with the following two differences:
- There must be no newline (‘\n’) at the end.
- The special ‘%%b’ spec can be used to display the buffer name.
Well, it's no spec at all, really—‘%%’ is just a way to quote
‘%’ to allow it to pass through the formatting machinery unmangled,
so that Emacs receives ‘%b’, which is something the Emacs mode line
display interprets to mean “show the buffer name”. For a full list of
mode line specs Emacs understands, see the documentation of the