zsh/Functions/Misc/add-zle-hook-widget

# Add to HOOK the given WIDGET
# 
# HOOK is one of isearch-exit, isearch-update, line-pre-redraw, line-init,
# line-finish, history-line-set, keymap-select (the zle- prefix is allowed
# but not required).  If a widget corresponding to HOOK already exists, it
# is preserved and called first in the new set of HOOK widgets.
#
# With -d, remove the WIDGET from the hook instead; deletes the hook
# linkage if it is empty.
#
# -D behaves like -d, but pattern characters are active in WIDGET, so
# any matching widget will be deleted from the hook.
#
# Without -d, if the WIDGET is not already defined, a function having the
# same name is marked for autoload; -U is passed down to autoload if that
# is given, as are -z and -k.  (This is harmless if the function is
# already defined.)  The WIDGET is then created with zle -N.
#
# The -L option lists the hooks and their associated widgets.

# This is probably more safeguarding than necessary
zmodload -e zsh/zle || return 1
{ zmodload zsh/parameter && zmodload zsh/zleparameter } || {
    print -u2 "add-zle-hook-widget: Need parameter modules for zle hooks"
    return 1
}

() { # Preserve caller global option settings

emulate -L zsh

# Setup - create the base functions for hook widgets that call the others

local -a hooktypes=( zle-isearch-exit zle-isearch-update
                     zle-line-pre-redraw zle-line-init zle-line-finish
                     zle-history-line-set zle-keymap-select )
# Stash in zstyle to make it global
zstyle zle-hook types ${hooktypes#zle-}

# Relying on multifuncdef option here
function azhw:${^hooktypes} {
    local -a hook_widgets
    local hook
    # Values of these styles look like number:name
    # and we run them in number order
    zstyle -a $WIDGET widgets hook_widgets
    for hook in "${(@)${(@on)hook_widgets[@]}#<->:}"; do
	if [[ "$hook" = user:* ]]; then
	    # Preserve $WIDGET within the renamed widget
	    zle "$hook" -f "nolast" -N -- "$@"
	else
	    zle "$hook" -f "nolast" -Nw -- "$@"
	fi || return
    done
    return 0
}

# Redefine ourself with the setup left out

function add-zle-hook-widget {
    local -a hooktypes
    zstyle -a zle-hook types hooktypes

    # This part copied from add-zsh-hook
    local usage="Usage: $funcstack[1] hook widgetname\nValid hooks are:\n  $hooktypes"

    local opt
    local -a autoopts
    integer del list help

    while getopts "dDhLUzk" opt; do
	case $opt in
	    (d)
	    del=1
	    ;;

	    (D)
	    del=2
	    ;;

	    (h)
	    help=1
	    ;;

	    (L)
	    list=1
	    ;;

	    ([Uzk])
	    autoopts+=(-$opt)
	    ;;

	    (*)
	    return 1
	    ;;
	esac
    done
    shift $(( OPTIND - 1 ))

    1=${1#zle-}	# Strip prefix not stored in zle-hook types style

    if (( list )); then
	zstyle -L "zle-(${1:-${(@j:|:)hooktypes[@]}})" widgets
	return $?
    elif (( help || $# != 2 || ${hooktypes[(I)$1]} == 0 )); then
	print -u$(( 2 - help )) $usage
	return $(( 1 - help ))
    fi

    local -aU extant_hooks
    local hook="zle-$1"
    local fn="$2"

    if (( del )); then
        # delete, if hook is set
	if zstyle -g extant_hooks "$hook" widgets; then
	    if (( del == 2 )); then
		set -A extant_hooks ${extant_hooks[@]:#(<->:|)${~fn}}
	    else
		set -A extant_hooks ${extant_hooks[@]:#(<->:|)$fn}
	    fi
            # unset if no remaining entries
	    if (( ${#extant_hooks} )); then
		zstyle "$hook" widgets "${extant_hooks[@]}"
	    else
		zstyle -d "$hook" widgets
	    fi
	fi
    else
	# Check whether attempting to add a widget named for the hook
	if [[ "$fn" = "$hook" ]]; then
	    if (( ${+widgets[$fn]} )); then
		print -u2 "$funcstack[1]: Cannot hook $fn to itself"
		return 1
	    fi
	    # No point in building the array until another is added
	    autoload "${autoopts[@]}" -- "$fn"
	    zle -N "$fn"
	    return 0
	fi
	integer i=${#options[ksharrays]}-2
	zstyle -g extant_hooks "$hook" widgets
        # Check for an existing widget, add it as the first hook
	if [[ ${widgets[$hook]:-} != "user:azhw:$hook" ]]; then
	    if [[ -n ${widgets[$hook]:-} ]]; then
		zle -A "$hook" "${widgets[$hook]}"
		extant_hooks=(0:"${widgets[$hook]}" "${extant_hooks[@]}")
	    fi
	    zle -N "$hook" azhw:"$hook"
	fi
	# Add new widget only if not already in the hook list
	if [[ -z ${(M)extant_hooks[@]:#(<->:|)$fn} ]]; then
       	    # no index and not already hooked
            # assign largest existing index plus 1
	    i=${${(On@)${(@M)extant_hooks[@]#<->:}%:}[i]:-0}+1
	else
	    return 0
	fi
	extant_hooks+=("${i}:${fn}")
	zstyle -- "$hook" widgets "${extant_hooks[@]}"
	if (( ! ${+widgets[$fn]} )); then
	    autoload "${autoopts[@]}" -- "$fn"
	    zle -N -- "$fn"
	fi
	if (( ! ${+widgets[$hook]} )); then
	    zle -N "$hook" azhw:"$hook"
	fi
    fi
}

} "$@" # Resume caller global options

# Handle zsh autoloading conventions:
# - "file" appears last in zsh_eval_context when "source"-ing
# - "evalautofunc" appears with kshautoload set or autoload -k
# - "loadautofunc" appears with kshautoload unset or autoload -z
# - use of autoload +X cannot reliably be detected, use best guess
case "$zsh_eval_context" in
*file) ;;
*evalautofunc) ;;
*loadautofunc) add-zle-hook-widget "$@";;
*) [[ -o kshautoload ]] || add-zle-hook-widget "$@";;
esac
# Note fallback here is equivalent to the usual best-guess used by
# functions written for zsh before $zsh_eval_context was available
# so this case-statement is backward-compatible.