When two or more zle-line-pre-redraw hooks are registered using
add-zle-hook-widget, the value of $LASTWIDGET when the each hook is
called is the name of the former hook:

    [Eric Freese wrote in https://github.com/zsh-users/zsh-autosuggestions/issues/529#issuecomment-632113840]
    $ zsh -df
    % autoload add-zle-hook-widget
    % f() {}
    % g() { zle -M "$(typeset -p LASTWIDGET)" }
    % add-zle-hook-widget line-pre-redraw f
    % add-zle-hook-widget line-pre-redraw g
    % x<CURSOR>
    typeset -r LASTWIDGET=f

The issue here is that g would like to to know what widget was invoked
immediately before the redraw.  In the example, that'd be self-insert.

I've attached two proofs of concept.  WDYT?

I'll add docs, etc, once an approach is chosen.

Cheers,

Daniel

P.S.  For the latter patch, note that «zle $widget -f» is distinct from
«zle -f».