1 files changed, 424 insertions, 0 deletions

diff --git a/src/twopane.bash b/src/twopane.bash
new file mode 100755
index 0000000..39a6bfb
--- /dev/null
+++ b/src/twopane.bash
@@ -0,0 +1,424 @@
+#!/bin/bash
+BASH_ARGV0=twopane.bash
+echo -n "$0" >/proc/$$/comm
+set -e
+set -f
+set -o pipefail
+shopt -s lastpipe
+
+BOT_SIZE=8
+BOT_TITLE=input
+
+if [ $# = 0 ]
+then
+        TOP_CMD="$SHELL -i"
+        BOT_CMD=background
+        TOP_EXIT=prompt
+        #BOT_CMD=start
+        #TOP_EXIT=restart
+else
+        TOP_CMD=$*
+        BOT_CMD=start
+        TOP_EXIT=quit
+fi
+TOP_TITLE="Command: $TOP_CMD"
+
+TWOPANE=$(mktemp -d)
+export TWOPANE TOP_CMD BOT_CMD TOP_TITLE BOT_TITLE BOT_SIZE
+trap 'rm -r "$TWOPANE"' EXIT
+STY=twopane.${TWOPANE##*/}
+
+save_file()
+{
+        cat > "$TWOPANE"/"${1:?$0: Error: filename cannot be empty string}"
+}
+
+save_screenrc()
+{
+        save_file screenrc"${1:+.$1}"
+}
+
+save_screenrc <<'.'
+# Disable keybindings.
+unbindall
+escape \0\0
+# Disable messages.  This is needed for screen -X/-Q to work reasonably.
+msgwait 0
+msgminwait 0
+# Try to disable blocking the terminal on ^S.
+# Doesn't seem to work here.
+# More is needed.  Xterm?
+nonblock on
+
+caption string '%t'
+layout new
+split
+focus bottom
+resize $BOT_SIZE
+screen -ln -t "$BOT_TITLE" 0 bash --noprofile --rcfile "$TWOPANE"/bashrc -i
+layout save 0
+.
+
+check_top()
+{
+        screen -p1 -Q info >/dev/null
+}
+
+kill_top()
+{
+        while check_top
+        do
+                screen -p1 -X kill
+        done
+}
+
+start_top()
+{
+        if check_top
+        then
+                return
+        fi
+        if [ $# = 0 ]
+        then
+                set -f
+                set -- ${TOP_CMD:-bash -i}
+        fi
+        TOP_TITLE="Command: ${*@Q}"
+        screen -X focus top
+        screen -X screen -ln -t "$TOP_TITLE" 1 "$@"
+        screen -p1 -X exec .!. sh -c 'exec socat UNIX-LISTEN:"$TWOPANE"/socket STDIN,cfmakeraw!!STDOUT'
+}
+
+restart_top()
+{
+        kill_top
+        start_top "$@"
+}
+
+socat_connect()
+{
+        socat STDIN!!STDOUT UNIX-CONNECT:"$TWOPANE"/socket,forever
+}
+
+# Start SOCAT if necessary.
+# Connect the running SOCAT to file descriptors.
+# Optionally assign the file descriptors to the specified variables.
+# Optionally assign the socat PID to the specified variable.
+#
+# The copied file descriptors (unlike the original coprocess file
+# descriptors, in ${SOCAT[0]} and ${SOCAT[1]}) can be passed to external
+# processes (e.g.: other socat(1) instances) and used in subshells.
+connect()
+{
+        case $# in
+                3 | 5 )
+                        declare -n pid="$1" std0="$2" std1="$3"
+                        shift 3
+                        ;;
+                2 | 4 )
+                        local pid
+                        declare -n std0="$1" std1="$2"
+                        shift 2
+                        ;;
+                0 )
+                        local std0 std1 pid
+                        ;;
+                * )
+                        return 1
+                        ;;
+        esac
+        if ! [ "${SOCAT[0]}" ]
+        then
+                local STDERR
+                exec {STDERR}>&2
+                {
+                        coproc SOCAT { socat_connect; } 2>&$STDERR
+                } 2>/dev/null
+                eval "exec $STDERR>&-"
+        fi
+        pid=${SOCAT_PID}
+        exec {std0}<&${SOCAT[0]} {std1}>&${SOCAT[1]}
+        disown
+}
+
+sendc()
+{
+        [ "${SOCAT[0]}" ] || connect
+        printf '%s' "$*" >&${SOCAT[1]}
+}
+
+send()
+{
+        [ "${SOCAT[0]}" ] || connect
+        printf '%s\n' "$*" >&${SOCAT[1]}
+}
+
+disconnect()
+{
+        if [ $# = 2 ]
+        then
+                declare -i -n std0="$1" std1="$2"
+                eval "exec $std0<&- $std1>&-"
+                unset std0 std1
+        fi
+        wait -f "$SOCAT_PID" 2>/dev/null
+}
+
+restart()
+{
+        start "$@"
+}
+
+start()
+{
+        foreground "$@"
+}
+
+background()
+{
+        start_top "$@"
+        focus bottom
+        connect stdin stdout
+}
+
+foreground_loop()
+{
+        while true
+        do
+                start_top "$@"
+                connect stdin stdout
+                forward
+                disconnect stdin stdout
+
+                case "$TOP_EXIT" in
+                        restart )
+                                continue ;;
+                        quit )
+                                exit ;;
+                        prompt | * )
+                                focus bottom
+                                break
+                        ;;
+                esac
+        done
+}
+
+forwarding()
+{
+        [ "$FORWARD_PID" ] || return
+        FORWARD_JOBSPEC=$(jobs -sl | pid_to_jobspec "$FORWARD_PID")
+        [ "$FORWARD_JOBSPEC" ]
+}
+
+forward()
+{
+        declare -g FORWARD_PID
+        if ! check_top
+        then
+                echo "$0: Warning: Nothing to forward.  Starting anew." >&2
+                background "$@"
+        elif forwarding
+        then
+                resume_forward
+                return
+        fi
+
+        focus top
+        old_stty=$(stty -g)
+        # Lowercase $stdin/$stdout are the SOCAT coprocess connected to
+        # the other pane's terminal.  Uppercase $STDIN/$STDOUT are the
+        # real stdin/stdout of this function, connected to the lower
+        # pane's terminal.  Socat here merges inputs from both sources.
+        exec {STDIN}<&0 {STDOUT}>&1 {STDERR}>&2
+
+        # The input is put out raw back over the socket.  The input is
+        # copied to stdout after being filtered (to display control
+        # characters with carrot-encoding like '^[' etc).
+        exec {TEE}> >(tee >(output_filter >&$STDOUT) >&$stdout)
+        stty=cfmakeraw,opost=1,onlcr=1
+        {
+                socat FD:$STDIN,$stty!!STDOUT - <&$stdin >&$TEE 2>&$STDERR &
+        } 2>/dev/null
+        FORWARD_PID=$!
+        printf '%s\n' "#!/bin/bash" "kill $!" "screen -X focus bottom" > "$TWOPANE"/unforward
+        chmod +x "$TWOPANE"/unforward
+        fg >/dev/null
+        stty "$old_stty"
+        focus bottom
+        echo
+}
+
+cfmakeraw()
+{
+        cmd=(stty -ignbrk -brkint -parmrk -istrip -inlcr -igncr -icrnl
+        -ixon -opost -echo -echonl -icanon -isig -iexten -parenb cs8)
+        "${cmd[@]}" "$@"
+}
+
+pid_to_jobspec()
+{
+        while read jspec pid status cmd
+        do
+                [ "$pid" = "$1" ] || continue
+                jspec=${jspec%]*}
+                jspec=%${jspec#[}
+                echo $jspec
+                return
+        done
+        false
+}
+
+resume_forward()
+{
+        old_stty=$(stty -g)
+        cfmakeraw opost onlcr
+        focus top
+        fg "$FORWARD_JOBSPEC" >/dev/null
+        stty "$old_stty"
+        focus bottom
+}
+
+foreground()
+{
+        if forwarding
+        then
+                resume_forward
+        else
+                foreground_loop "$@"
+        fi
+}
+
+twopane()
+{
+        start "$@"
+}
+
+quit()
+{
+        screen -X quit
+}
+
+focus()
+{
+        screen -X focus "$@"
+}
+
+output_filter()
+{
+        tokenize | colorize | soft_cursor
+}
+
+# if (show_nonprinting) {
+#     while (true)
+#       {
+#         if (ch >= 32) {
+#             if (ch < 127) *bpout++ = ch;
+#             else if (ch == 127) {*bpout++ = '^'; *bpout++ = '?';}
+#             else {
+#                 *bpout++ = 'M';
+#                 *bpout++ = '-';
+#                 if (ch >= 128 + 32) {
+#                     if (ch < 128 + 127) *bpout++ = ch - 128;
+#                     else {*bpout++ = '^'; *bpout++ = '?';}}
+#                 else {*bpout++ = '^'; *bpout++ = ch - 128 + 64;}}}
+#         else if (ch == '\t' && !show_tabs) *bpout++ = '\t';
+#         else if (ch == '\n') {newlines = -1; break;}
+#         else {*bpout++ = '^'; *bpout++ = ch + 64;}
+#         ch = *bpin++;}}
+
+chr()
+{
+        declare -i n="$*"
+        printf "\\$(printf %o "$n")"
+}
+
+colorize()
+{
+        while read -r
+        do
+                case "$REPLY" in
+                        \\[0-7][0-7][0-7] ) ;;
+                        * )
+                                printf '%s\n' "$REPLY"
+                                continue
+                                ;;
+                esac
+                declare -i c=8#"${REPLY#?}"
+                if (( c > 128 + 127 ))
+                then
+                        :
+                elif (( c > 128 + 32 ))
+                then
+                        printf -v REPLY "M-$(chr c - 128)"
+                elif (( c > 127 ))
+                then
+                        printf -v REPLY "M-^$(chr c - 128 + 64)"
+                elif (( c < 32 ))
+                then
+                        printf -v REPLY "^$(chr c + 64)"
+                fi
+                printf $'\e[1m%s\e[m\n' "$REPLY"
+        done
+}
+
+tokenize()
+{
+        while read -r -N1
+        do
+                if [[ "$REPLY" =~ [[:print:]] ]]
+                then
+                        # Output one printable character per line. It may be a
+                        # multibyte unicode character.
+                        printf '%s\n' "$REPLY"
+                        continue
+                else
+                        # If it is a non-printable, then we output a
+                        # multi-character line. In this case we colorize it
+                        # later so that it won't be confused with multiple
+                        # printable characters.
+                        printf '\\%.3o\n' "'$REPLY"
+                        continue
+                fi
+        done
+}
+
+soft_cursor()
+{
+        FMT=$'%s \b\e[%sm \e[m\b'
+        REPLY=
+        while printf "$FMT" "$REPLY" $(( 101 + RANDOM % 7 ))
+        do
+                read -r || break
+        done
+}
+
+our_bashrc_main()
+{
+        set -f
+        set -o pipefail
+        trap "screen -X quit" EXIT
+        export PS1="$BOT_TITLE\\\$ "
+}
+
+save_file bashrc <<.
+BASH_ARGV0=twopane
+echo -n "\$0" >/proc/\$\$/comm
+${TOP_CMD@A}
+${BOT_CMD@A}
+${TOP_TITLE@A}
+${BOT_TITLE@A}
+
+${TOP_EXIT@A}
+
+$(declare -f)
+our_bashrc_main
+
+$BOT_CMD
+.
+
+main()
+{
+        screen -c "$TWOPANE"/screenrc -m -S "$STY" -ln
+}
+
+main "$@"