speedbar-dynamic-tags-function-list

speedbar-dynamic-tags-function-list is a variable defined in `speedbar.el'.
Its value is

((speedbar-fetch-dynamic-imenu . speedbar-insert-imenu-list)
 (speedbar-fetch-dynamic-etags . speedbar-insert-etags-list))

Documentation:
Set to a list of functions which will return and insert a list of tags.
Each element is of the form ( FETCH . INSERT ) where FETCH
is a function which takes one parameter (the file to tag) and returns a
list of tags. The tag list can be of any form as long as the
corresponding insert method can handle it. If it returns t, then an
error occurred, and the next fetch routine is tried.
INSERT is a function which takes an INDENTation level, and a LIST of
tags to insert. It will then create the speedbar buttons.