bash: send stdout to a handler in a process substitution via exec and wait for it to be finished with processing input (SIGSTOP/SIGCONT)

x.sh

#!/usr/bin/env bash

function setup {
    typeset -g "$1" 2>/dev/null && {
        typeset -n fd=$1;
        ((${!fd})) &&
            exec {fd}>&-;
        exec {fd}> >('handler');
    };
};

function msg {
    if
        ((${1:?}));
    then
        typeset fd=${!1};
        fd=${fd:?};
    else
        return 1;
    fi;

    shift 1;

    [[ -f /dev/stdin || -p /dev/stdin ]] &&
        cat /dev/stdin 1>&${fd};

    (($#)) &&
        printf '%s\n' "$@" 1>&${fd};
};

function sig_stop {
    kill -s SIGSTOP "${1:-$$}";
};

function sig_cont {
    kill -s SIGCONT "${1:-$$}";
};

# -- MAIN.

set +m;

# an example
echo Nr 1.;

(

function handler {
    ti_red_f=$(tput setaf 1);
    ti_reset="$(tput sgr0 || tput me)";

    while
        IFS= read -r;
    do
        case $REPLY in
            (resume' '?*)
                'sig_cont' ${REPLY#resume };
                continue;
        esac;
        sleep .5;
        printf '%s\n' "${ti_red_f}${REPLY}${ti_reset}";
    done;
};

read -r pid _  < /proc/self/stat;

echo bang!;
echo;

'setup' myfd;

printf '%s\n' foo bar | 
'msg' myfd "fo o" bar "resume $pid" &

'sig_stop' $pid;


echo;
echo resuuumed!;

);

set -m;

# vim: set ts=4 sw=4 tw=0 et :

$ x.sh
$ . x.sh
$ (. x.sh)