Running a nested xfce4-session in Xephyr

capture.sh

#!/bin/bash

DISPLAY=:15
X=0
Y=0
X11GRAB_OPTS=( -show_region 1 )

shopt -s extglob

while [ ! -z "$1" ]
do
    case "$1" in
        :*)     DISPLAY="$1"
                shift
                ;;

        +([0-9])x+([0-9]))
                read W H < <(tr -c "[0-9]" " " <<< "$1")
                shift
                ;;

        +([0-9])x+([0-9])++([0-9])++([0-9]))
                read W H X Y < <(tr -c "[0-9]" " " <<< "$1")
                shift
                ;;

        --nomouse)
                X11GRAB_OPTS+=( -draw_mouse 0 )
                shift
                ;;

        *)      OUTFILE="$1"
                shift
                ;;
    esac
done

[ -f "${OUTFILE}" ] && {
    echo "${OUTFILE} already exists. Aborting." >&2
    exit 1
}

if which play > /dev/null 2>&1 ; then
    (
        sleep 1.0
        play  -n -c1 synth .2 sin 440 gain -12

        if which espeak > /dev/null 2>&1 ; then
            sleep 0.25
            echo "$(basename "${OUTFILE%.*}")" | espeak
        fi
    
    ) &
fi


while IFS=": " read key value ; do
    echo "key=|$key| value=|$value|"
    case "$key" in
        Width) DWIDTH=$value
                echo W
                ;;
        Height) DHEIGHT=$value
                ;;
    esac
done < <(xwininfo -display "${DISPLAY}" -root)

[ -z "${W}" ] && W="${DWIDTH}"
[ -z "${H}" ] && H="${DHEIGHT}"

ffmpeg -y \
  -f x11grab -thread_queue_size 512 -vsync cfr -framerate 25 \
  -video_size "${W}x${H}" \
  "${X11GRAB_OPTS[@]}" \
  -i "${DISPLAY}.0+$X,$Y" \
  -f alsa -thread_queue_size 2048 -acodec pcm_s24le -sample_rate 44100 -ac 1 -i pulse \
  -c:a pcm_s16le \
  -c:v libx264 -pix_fmt yuv420p -preset ultrafast -tune animation -qp 1 \
  -map 0:0,0:0 -map 1:0,0:0 \
  -timecode 00:00:00:00 \
  "$OUTFILE"

grantpt.c

#define _XOPEN_SOURCE
#include <stdlib.h>
#include <stdio.h>

int main() {
    return grantpt(0);
}

Makefile

all: pts grantpt ptsname unlockpt

nested-xfce4-session.sh

#!/bin/bash

function usage() {
    nroff -mandoc <<-EOF | less
.TH $(basename $0) 1
$(basename $0) - open a nested X terminal
.SH SYNOPSIS
$(basename $0) [displayid] [displaysize | --fullscreen] [userlogin] [homedir]

$(basename $0) \-\-help

.SH OPTIONS

.TP
.BR \fIdisplayid\fR
Virtual display to create
Default is :15
.TP
.BR \fIdisplaysize\fR
Size of the virtual display
Default is 1280x720
.TP
.BR \fIuserlogin\fR
Open a session with the given identity.
Default is the current user. Opening a session as a different user require sudo access.
.TP
.BR \fIhomedir\fR
Set the \fIHOME\fR directory for the nested session.
Useful to run xfce4 in a clean and distinct environment 
from yours.  The nested session owner should have 
read/write access to the directory.

.SH EXAMPLE
  ./nested-xfce4-session.sh 
      Start a new X11 server and run xfce4-session

  ./nested-xfce4-session.sh :12
      Start a new X11 server as DISPLAY :12 and run xfce4-session

  ./nested-xfce4-session.sh :12 640x480
      Start a new X11 server as DISPLAY :12 
      with a screen size of 640x480 and run xfce4-session
      (eventually screen size will be resized according to
      your host xfce4 configuration)

  ./nested-xfce4-session.sh /tmp/temp.dir
      Start a new X11 server and run xfce4-session with the
      home directory set to /tmp/temp.dir.
EOF
}

SCREEN="1280x720"
USER=$(whoami)
GUEST_DISPLAY=":15"
EXTRA=( -dpi 96 )
REMOTE=

shopt -s extglob
declare -A OPTS

while [ ! -z "$1" ]
do
    case "$1" in
        -?(-)help)
                usage
                exit 0
                ;;

        +([0-9])x+([0-9]))
                SCREEN="$1"
                shift
                ;;

        --fullscreen)
                EXTRA+=( -fullscreen )
                shift
                ;;

        :+([0-9]))
                GUEST_DISPLAY="$1"
                shift
                ;;
        
	*@*)	USER="$1"
		REMOTE=true
		shift
		;;

        *)      if id -u "$1" > /dev/null 2>&1 ; then
                    # valid user name on that system
                    USER="$1"
                    shift
                elif [ -d "$1" ] ; then
                    # valid directory
                    OPTS[HOME]="HOME=\"$1\""
                    shift
                else
                    echo Not a known user or directory : "$1" >&2
                    exit 1
                fi
                ;;
    esac
done

# Prepare the client to run when server will be ready
LAUNCHER="/bin/bash"

#if [ "${USER}" != $(whoami) ]
#    LAUNCHER="sudo -u ${USER} -b -i"
#then
#else
#    LAUNCHER="env -i PATH=${PATH} 
#                     DISPLAY=${GUEST_DISPLAY} 
#                     HOME=${HOME} 
#                     LOGNAME=${LOGNAME}
#                     USER=${USER} bash -c"
#fi

TEMPDIR=$(mktemp -d)
FIFO="${TEMPDIR}/fifo"
mkfifo "${FIFO}"
chmod a+r "${FIFO}"
chmod a+x "${TEMPDIR}"
exec 3<>"${FIFO}"

APP=xfce4-session
#APP=xterm
if [ -n "$REMOTE" ]
then
    DISPLAY=${GUEST_DISPLAY} ssh -fCY ${USER} "sleep 5 && echo \$DISPLAY && unset XAUTHORITY && "${OPTS[@]}" ${APP}"
else
    LAUNCHER="sudo -u ${USER} -b -i bash -c"
    DISPLAY=${GUEST_DISPLAY} ${LAUNCHER} "read DISPLAY < '${FIFO}' && \
                    unset XAUTHORITY && \
                    "${OPTS[@]}" DISPLAY=\":\${DISPLAY}\" $APP"
fi

Xephyr -displayfd 3 \
       -sw-cursor -reset -terminate \
       "${GUEST_DISPLAY}" -screen "${SCREEN}" "${EXTRA[@]}"

rm -rf "${TEMPDIR}"

wait

pts.c

#define _XOPEN_SOURCE
#include <stdlib.h>
#include <stdio.h>

int main() {
    int status;
    
    status = grantpt(0);
    if (status)
        return status;

    status = unlockpt(0);
    if (status)
        return status;
    
    char *pts = ptsname(0);
    printf("%s\n", pts ? pts : "");
    return pts ? 0 : 1;
}

ptsname.c

#define _XOPEN_SOURCE
#include <stdlib.h>
#include <stdio.h>

int main() {
    char *pts = ptsname(0);
    printf("%s\n", pts ? pts : "");
    return 0;
}

run-in-terminal.sh

#!/bin/bash

GEOMETRY="80x24"
USER=$(whoami)
GUEST_DISPLAY=":15"
WINNAME=$(uuidgen || echo $RANDOM)
EXTRA=( --disable-server --title "$WINNAME" )
OUTFILE="out.mov"

shopt -s extglob
declare -A OPTS
OPTS[HOME]=""

while [ ! -z "$1" ]
do
    case "$1" in
        -?(-)help)
                usage
                exit 0
                ;;

        +([0-9])x+([0-9])*)
                GEOMETRY="$1"
                shift
                ;;

        --fullscreen)
                EXTRA+=( --fullscreen )
                shift
                ;;

        :+([0-9]))
                GUEST_DISPLAY="$1"
                shift
                ;;

        *.mov)  OUTFILE="$1"
                shift
                ;;

        *)      if id -u "$1" > /dev/null 2>&1 ; then
                    # valid user name on that system
                    USER="$1"
                    shift
                elif [ -d "$1" ] ; then
                    # valid directory
                    OPTS[HOME]="$1"
                    shift
                else
                    echo Not a known user or directory : "$1" >&2
                    exit 1
                fi
                ;;
    esac
done

TEMPDIR=$(mktemp -d)
COMP="${TEMPDIR}/comp"
CTRL="${TEMPDIR}/ctrl"
FIFO="${TEMPDIR}/fifo"
mkfifo "${COMP}"
mkfifo "${CTRL}"
mkfifo "${FIFO}"
chmod a+r "${COMP}"
chmod a+r "${FIFO}"
chmod a+x "${TEMPDIR}"
#exec 3<>"${FIFO}"

typeit() {
  while IFS='' read -rn1 C; do
    if [ -z "${C}" ] ; then
        echo
    else
        echo -n "$C"
    fi
    sleep .$((1+$RANDOM/15000))
    [ -z "${C}" ] && sleep 1.5 # extra delay after end-of-line
  done
}


sudo -u "${USER}" -b -i xfce4-terminal --geometry="${GEOMETRY}" \
                                       --display="${GUEST_DISPLAY}" \
                                       --hide-menubar \
                                       --hide-toolbar \
                                       --hide-scrollbar \
                                       "${EXTRA[@]}" -x bash -c \
                                       'cat < '"${FIFO}"' ; read < '"${COMP}"

sleep 1
# At this point, the terminal window is blocked.
# Start capture
./capture.sh --nomouse "${GUEST_DISPLAY}" \
    $(./window-geometry.sh "${GUEST_DISPLAY}" "${WINNAME}") \
    "${OUTFILE}" < "${CTRL}" &

CAPTUREPID="$!"
echo "${CAPTUREPID}"
echo  > "${CTRL}"

# For obscure reasons, the following line will put the process to
# the background when reading from stdin ?!?
# Maybe `stty -tostop` would FIX that ?
# See http://www.linusakesson.net/programming/tty/

# This require a PTS, not a Pipe so 'bash -i' will be totally
# "fooled" in thinking it is connected to a terminal
exec 3<>/dev/ptmx
sudo -u "${USER}" echo -n # <- hack to force authentication here
PTS=$(./pts <&3)
echo $?
# sudo -u "${USER}" ./grantpt <&3
# echo $?
# ./unlockpt <&3
# echo $?
# PTS=$(./ptsname <&3)
# echo $?

echo PTS is ${PTS}

# stty -F "${PTS}" cooked echo iutf8 rows 22 columns 80
# stty -F "${PTS}" --all

(
    sleep 3
    typeit
    sleep 1

    # Take a screenshot after completion
    xwd -silent -display "${GUEST_DISPLAY}" -name "${WINNAME}" | \
        convert xwd:- "${OUTFILE%.*}.png"

    echo exit
) >&3 < /dev/stdin &

sudo -nSu "${USER}" \
bash -c "
    cd \"${OPTS[HOME]:-\$HOME}\"
    bash -i
" <"${PTS}" 2>&1 | tee "${OUTFILE%.*}.log" >"${FIFO}" 


exec 3>&-

sleep 1
echo 'q' > "${CTRL}"
wait

# Exit terminal
echo 'done' > "${COMP}"

#kill -SIGTERM "${CAPTUREPID}"
rm -rf "${TEMPDIR}"

unlockpt.c

#define _XOPEN_SOURCE
#include <stdlib.h>
#include <stdio.h>

int main() {
    return unlockpt(0);
}

window-geometry.sh

#!/bin/bash

# Assume window title is $1
# FIXME enforce that !

DISPLAY=:15
WINNAME=""

shopt -s extglob

while [ ! -z "$1" ]
do
    case "$1" in
        :*)     DISPLAY="$1"
                shift
                ;;


        *)      WINNAME="$1"
                shift
                ;;
    esac
done

[ -z "${WINNAME}" ] && {
    echo "Missing window name Aborting." >&2
    exit 1
}

declare -A WINPROPS

while IFS=": " read key value ; do
    if [ -n "$key" ]; then
        # echo "key=|$key| value=|$value|" >&2
        WINPROPS["$key"]="$value"
    fi
done < <(xwininfo -display "${DISPLAY}" -name "$WINNAME")

printf "%sx%s%s\n" \
    "${WINPROPS[Width]}" \
    "${WINPROPS[Height]}" \
    "${WINPROPS[Corners]%% *}"

Your codes helped me a lot. Thank you so much!