Create a virtual screen and allow connecting to it via VNC

vncscreen

#!/bin/sh
#
# Create a virtual screen and allow connecting to it via VNC
#
# Based on:
# - https://bbs.archlinux.org/viewtopic.php?id=191555
# - https://bitbucket.org/denilsonsa/small_scripts/src/default/screenlayout/create-virtual-modelines.sh?fileviewer=file-view-default
#
# GistID: 90c34e47689cbef235fe76251706c7d0

set -e

###
# Configure virtual screen with defined modeline
#
# $*: Modeline definition, passed to gtf(1)
add_modeline ()
{
    local primaryoutput virtualoutput
    local modeline name

    primaryoutput="$(
        xrandr | grep ' connected primary' | cut -d' ' -f1 | head -n1
    )"
    if [ -z "${primaryoutput}" ]
    then
        echo "ERROR: Failed to determine primary output"
        exit 1
    fi

    virtualoutput="$(
        xrandr | grep 'VIRTUAL' | cut -d' ' -f1 | head -n1
    )"
    if [ -z "${virtualoutput}" ]
    then
        echo "ERROR: Failed to determine virtual output"
        exit 1
    fi

    modeline="$(
        gtf "$@" | sed -n 's/.*Modeline "\([^" ]\+\)" \(.*\)/\1 \2/p'
    )"
    if [ -z "${modeline}" ]
    then
        echo "ERROR: Failed to calculate modeline: $*"
        exit 1
    fi

    name="$(
        echo "${modeline}" | sed 's/\([^ ]\+\) .*/\1/'
    )"
    if [ -z "${name}" ]
    then
        echo "ERROR: Failed to get name from modeline: ${modeline}"
        exit 1
    fi


    xrandr \
        --output "${virtualoutput}" --off \
        --output "${primaryoutput}" --auto

    xrandr --delmode "${virtualoutput}" "${name}" || :
    xrandr --rmmode "${name}" || :

    # shellcheck disable=SC2086
    xrandr --newmode ${modeline}
    xrandr --addmode "${virtualoutput}" "${name}"

    xrandr \
        --output "${virtualoutput}" \
        --mode "${name}" \
        --right-of "${primaryoutput}"
}


# iPad Air 2 is 2048×1536
add_modeline 1024 768 60

x11vnc -clip xinerama1 -forever -noxdamage -repeat

# TODO Clean up on Ctrl-C