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feat: Create script to automate virtual second screen #9

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254 changes: 254 additions & 0 deletions tablet-vnc.sh
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#!/bin/bash

# ---
# A script to create a virtual second screen on an unused display output.
# Ideal for use with an Android tablet and a VNC client.
# Based on the tutorial from: https://github.com/santiagofdezg/linux-extend-screen
# ---

# --- Configuration ---
# You can change the default values here or pass them as arguments.
DEFAULT_WIDTH=1920
DEFAULT_HEIGHT=1200
DEFAULT_REFRESH=60
DEFAULT_UNUSED_DISPLAY="DisplayPort-0"
DEFAULT_POSITION="left-of" # Options: left-of, right-of, above, below

# Temporary file to store the state of the created mode
STATE_FILE="/tmp/extended_screen_state"
PASS_FILE="/tmp/vnc_pass_$$"

# --- Functions ---

# Function to clean up temporary files and screen configuration on exit/interruption
cleanup() {
echo "" # Add a newline for cleaner output after ^C
echo "--- Interrupted: Cleaning up virtual screen and temporary files ---"

# Clean up the password file
rm -f "$PASS_FILE"

# Clean up the screen configuration if the state file exists
if [ -f "$STATE_FILE" ]; then
read -r UNUSED_DISPLAY MODE_NAME <"$STATE_FILE"

if [ -n "$UNUSED_DISPLAY" ] && [ -n "$MODE_NAME" ]; then
echo "Disabling display '$UNUSED_DISPLAY' and removing mode '$MODE_NAME'..."
# Turn off the display and remove the mode, redirecting output to prevent error spam
xrandr --output "$UNUSED_DISPLAY" --off >/dev/null 2>&1
xrandr --delmode "$UNUSED_DISPLAY" "$MODE_NAME" >/dev/null 2>&1
# Check if mode is still in use by another monitor before removing globally
if ! xrandr | grep -B1 "$MODE_NAME" | grep -q " connected"; then
xrandr --rmmode "$MODE_NAME" >/dev/null 2>&1
fi
fi
rm -f "$STATE_FILE"
fi
echo "Cleanup complete."
# Exit the script to prevent it from continuing after cleanup
exit 0
}

# Trap interruption signals (like Ctrl+C) to run the cleanup function
trap cleanup HUP INT QUIT TERM

# Function to display how to use the script
usage() {
echo "Usage: $0 {start|stop} [options]"
echo ""
echo "Actions:"
echo " start : Sets up and enables the virtual screen."
echo " stop : Disables and removes the virtual screen configuration."
echo ""
echo "Options for 'start':"
echo " --width <px> : Horizontal resolution (Default: $DEFAULT_WIDTH)"
echo " --height <px> : Vertical resolution (Default: $DEFAULT_HEIGHT)"
echo " --refresh <hz> : Refresh rate (Default: $DEFAULT_REFRESH)"
echo " --display <name> : Unused display output (e.g., HDMI-1) (Default: $DEFAULT_UNUSED_DISPLAY)"
echo " --position <pos> : Position relative to primary screen (Default: $DEFAULT_POSITION)"
echo " --password <pass> : (Optional) Set a password for the VNC connection."
echo " -h, --help : Show this help message."
echo ""
echo "Example: $0 start --width 1280 --height 800 --display HDMI-1 --password mysecret"
exit 1
}

# Function to check for required commands
check_dependencies() {
for cmd in xrandr gtf x11vnc ip hostname; do
if ! command -v "$cmd" &> /dev/null; then
echo "Error: Required command '$cmd' not found."
echo "Please install it to continue. (e.g., 'sudo apt install x11vnc iproute2')"
exit 1
fi
done
}

# --- Main Script Logic ---

# Check for dependencies first
check_dependencies

ACTION="$1"
shift # Consume the action (start/stop)

# Handle the action
case "$ACTION" in
start)
# Set default values
WIDTH=$DEFAULT_WIDTH
HEIGHT=$DEFAULT_HEIGHT
REFRESH=$DEFAULT_REFRESH
UNUSED_DISPLAY=$DEFAULT_UNUSED_DISPLAY
POSITION=$DEFAULT_POSITION
PASSWORD=""

# Parse named arguments
while [ "$#" -gt 0 ]; do
case "$1" in
--width) WIDTH="$2"; shift 2 ;;
--height) HEIGHT="$2"; shift 2 ;;
--refresh) REFRESH="$2"; shift 2 ;;
--display) UNUSED_DISPLAY="$2"; shift 2 ;;
--position) POSITION="$2"; shift 2 ;;
--password) PASSWORD="$2"; shift 2 ;;
-h|--help) usage ;;
*) echo "Unknown option: $1"; usage ;;
esac
done

# Auto-detect the primary display
PRIMARY_DISPLAY=$(xrandr | grep ' primary ' | awk '{print $1}')
if [ -z "$PRIMARY_DISPLAY" ];
then
echo "Error: Could not automatically detect the primary display."
exit 1
fi

echo "--- Starting Virtual Screen Setup ---"
echo "Primary Display: $PRIMARY_DISPLAY"
echo "Virtual Display: $UNUSED_DISPLAY at ${WIDTH}x${HEIGHT}@${REFRESH}Hz"
echo "Position: $POSITION $PRIMARY_DISPLAY"

# 1. Generate the modeline
REFRESH_FORMATTED=$(printf "%.2f" "$REFRESH")
MODE_NAME=$(printf "%sx%s_%s" "$WIDTH" "$HEIGHT" "${REFRESH_FORMATTED//./_}")

# 2. Check if the mode already exists. If not, create it.
if ! xrandr | grep -q "$MODE_NAME"; then
echo "Mode '$MODE_NAME' not found. Creating it..."
FULL_MODELINE=$(gtf "$WIDTH" "$HEIGHT" "$REFRESH" | grep 'Modeline')
if [ -z "$FULL_MODELINE" ]; then
echo "Error: Could not generate a modeline for the given resolution."
exit 1
fi
MODE_DETAILS=$(echo "$FULL_MODELINE" | awk '{$1=$2=""; print $0}')

echo "Creating new mode..."
xrandr --newmode "$MODE_NAME" $MODE_DETAILS || {
echo "Failed to create new mode."
exit 1
}
else
echo "Mode '$MODE_NAME' already exists. Using existing mode."
fi

# 3. Add the mode to the unused display
echo "Adding mode to display '$UNUSED_DISPLAY'..."
xrandr --addmode "$UNUSED_DISPLAY" "$MODE_NAME" || {
echo "Failed to add mode to display."
exit 1
}

# 4. Enable the output and position it
echo "Enabling and positioning display..."
xrandr --output "$UNUSED_DISPLAY" --mode "$MODE_NAME" --"$POSITION" "$PRIMARY_DISPLAY" || {
echo "Failed to enable and position display."
exit 1
}

sleep 2

# 5. Calculate the VNC clip region dynamically
echo "Calculating VNC clip region..."
VNC_X=0
VNC_Y=0
SCREEN_INFO=$(xrandr | grep "$UNUSED_DISPLAY" | grep -o '[0-9]*x[0-9]*+[0-9]*+[0-9]*')
if [[ $SCREEN_INFO =~ \+([0-9]+)\+([0-9]+)$ ]]; then
VNC_X=${BASH_REMATCH[1]}
VNC_Y=${BASH_REMATCH[2]}
echo "Detected screen position at ${VNC_X}, ${VNC_Y}"
else
echo "Warning: Could not automatically determine screen position for VNC. Defaulting to 0,0."
fi
VNC_CLIP="${WIDTH}x${HEIGHT}+${VNC_X}+${VNC_Y}"

# Save the state for the 'stop' command and the cleanup trap
echo "$UNUSED_DISPLAY $MODE_NAME" >"$STATE_FILE"

# 6. Start the VNC server
echo ""
echo "--- Starting VNC Server ---"
echo "Clipping region: $VNC_CLIP"
echo "Hostname: $(hostname)"
echo "Your IP addresses are:"
ip -4 addr show | grep -oP 'inet \K[\d.]+'
echo ""
echo "Connect your VNC client to one of the IPs above on port 5900."
echo "Press Ctrl+C in this terminal to stop the VNC server and clean up."
echo "Or run '$0 stop' in another terminal."

VNC_CMD="x11vnc -clip \"$VNC_CLIP\" -repeat -noxdamage -forever"
if [ -n "$PASSWORD" ]; then
echo "Using password protection."
# Use x11vnc's utility to create a properly formatted password file.
x11vnc -storepasswd "$PASSWORD" "$PASS_FILE"
VNC_CMD+=" -rfbauth $PASS_FILE"
fi

eval $VNC_CMD

echo "VNC server stopped."
# If VNC server stops for any reason other than Ctrl+C, run cleanup
# The trap handles Ctrl+C and exits, so this code won't be reached in that case.
cleanup
;;

stop)
echo "--- Stopping Virtual Screen ---"
if [ ! -f "$STATE_FILE" ]; then
echo "Warning: State file not found. Try running 'start' first."
exit 1
fi

read -r UNUSED_DISPLAY MODE_NAME <"$STATE_FILE"

if [ -z "$UNUSED_DISPLAY" ] || [ -z "$MODE_NAME" ]; then
echo "Error: Could not read valid settings from state file."
exit 1
fi

echo "Disabling display '$UNUSED_DISPLAY'..."
xrandr --output "$UNUSED_DISPLAY" --off

echo "Removing mode '$MODE_NAME' from display..."
xrandr --delmode "$UNUSED_DISPLAY" "$MODE_NAME" || echo "Warning: Could not delete mode from display. It might not have been added or is stuck."

if ! xrandr | grep -B1 "$MODE_NAME" | grep -q " connected"; then
echo "Deleting global mode '$MODE_NAME'..."
xrandr --rmmode "$MODE_NAME" || echo "Warning: Could not remove global mode. It may be stuck or was already removed."
else
echo "Mode '$MODE_NAME' is still in use by another monitor; not removing it."
fi

rm "$STATE_FILE"
echo "Virtual screen has been disabled and cleaned up."
;;

*)
usage
;;
esac

exit 0