startscreen.sh

#!/usr/bin/env bash

LAUNCHER_PACKAGE=com.farmerbb.taskbar

# Functions go here
function enable_desktop_mode {
	echo "This device doesn't have desktop mode enabled!!!!"
	echo "This will require enabling said option (done automatically)"
	echo "However for it to apply, your device needs to restart"
	read -p "Press any key restart your phone and continue with this script"

	adb shell settings put global force_desktop_mode_on_external_displays 1
	adb shell settings put global force_allow_on_external 1
	echo "Enabled desktop mode"

	# Prevents a bug where the display shows up before this option is enabled properly
	adb shell settings put global overlay_display_devices none

	# Just to make sure that everything's written to disk before the forced reboot
	adb shell sync
	sleep 2

	# You need to reboot aparently for it to apply
	adb reboot
	echo "Rebooting..."

	# Wait for it to reappear
	adb wait-for-device
	echo "Waiting for the device to respond"

	# Wait for the services to initialize
	sleep 20
}

function host_sanity_check {
	# Check if all the executables are present on the host device
	for i in adb scrcpy bc xdpyinfo tail pgrep; do
		which $i >/dev/null 2>&1
		[[ $? -ne 0 ]] && \
			echo "Please download $i and add it into your path before running this script." && \
			exit 1
	done
}

function target_sanity_check {
	[[ $(adb shell getprop ro.build.version.sdk) < 29 ]] && \
		echo "Sorry, desktop mode is only supported on Android 10 and up." && \
		exit 1

	# Check if all the executables are present on the target device
	for i in sh ps grep cut sort uniq head; do
		adb shell which $i >/dev/null 2>&1
		[[ $? -ne 0 ]] && \
			echo "Your Android device is missing '$i' and this script won't work without it. Sorry..." && \
			exit 1
	done

	launcherpresent=$(adb shell pm list package | grep $LAUNCHER_PACKAGE)
	if [ -z $launcherpresent ]; then
		echo "Taskbar not installed, please install it so that you wouldn't end"
		echo "up in a situation where the launcher is not installed"
		echo "https://github.com/nikp123/scrcpy-desktop/issues/7"
		echo
		echo "App link: https://play.google.com/store/apps/details?id=$LAUNCHER_PACKAGE"
		adb shell am start -a android.intent.action.VIEW -d "market://details?=$LAUNCHER_PACKAGE"
		read -p "Once you've installed the app, press any key to continue."
	fi
}

function get_display_params {
	if [[ -z $1 ]]; then
		RESOLUTION=$(xdpyinfo | grep dimensions | cut -d' ' -f 7)
	else
		RESOLUTION=$1
	fi

	if [[ -z $2 ]]; then
		DENSITY=$(echo "$(xdpyinfo | grep resolution | cut -d' ' -f 7 | cut -d'x' -f 1)*1.66666667" | bc | cut -d'.' -f 1)
	else
		DENSITY=$2
	fi

	TARGET_DISPLAY_MODE=$(echo $RESOLUTION/$DENSITY)
}

PAYLOAD_STORE_DIR=payload

TARGET_CONNECTION_TIMEOUT=1
TARGET_TMP_DIR=/data/local/tmp
TARGET_SCRIPT1=$TARGET_TMP_DIR/scrcpy-payload1.sh
TARGET_SCRIPT2=$TARGET_TMP_DIR/scrcpy-payload2.sh
TARGET_FILE=$TARGET_TMP_DIR/VerySpecificFileNameThatIsVeryUnlikelyToOverlapWithAnotherOneThatAlreadyExistJustForSure21341r124kajfosfhoshifosngvoierg.txt

# Background process used to keep track whether the connection is still alive
function keep_alive {
	number=0
	while true; do
		adb shell "echo $number > $TARGET_FILE"
		number=$(( (number+1)%2 ))
		sleep $TARGET_CONNECTION_TIMEOUT
	done
}

# Check if host is capable
host_sanity_check

# Wait for the device before the script does anything
adb wait-for-device

# Checks if the target device is capable
target_sanity_check

# Change secondary display behaviour
adb shell settings put global enable_freeform_support 1
adb shell settings put global force_resizable_activities 1

# Check if desktop mode is already enabled, if not, prompt the user and do the
# required steps
result=$(adb shell settings get global force_desktop_mode_on_external_displays)
if [ "$result" == "0" ]; then
	enable_desktop_mode
fi
result=$(adb shell settings get global force_allow_on_external)
if [ "$result" == "0" ]; then
	enable_desktop_mode
fi

get_display_params $1 $2

# Use the secondary screen option to generate the other screen
adb shell settings put global overlay_display_devices $TARGET_DISPLAY_MODE

# Wait for the display to appear
sleep 1

# Should work up until android 13 (later versions untested)
# Selects the first of found displays (todo add option to select manually if there is more than one external display
# so 3 in total because we ommit id=0 as it's the main display that doesn't show dektop mode - at least yet)
display=$(adb shell 'dumpsys display|grep mDisplayId=|cut -d "=" -f2|sort -n|uniq|grep -v "^0$"|head -n1')

# if fetching fails, try defaults
if [ "$display" = "" ]; then
	echo "Host system has incompatible settings. Sorry about that."

	# Screen res/DPI (doesn't accept all values unfortunately)
	TARGET_DISPLAY_MODE=1920x1080/120

	# Use the secondary screen option to generate the other screen
	adb shell settings put global overlay_display_devices $TARGET_DISPLAY_MODE

	# Wait for the display to appear
	sleep 1

	# Do your magic
	display=$(adb shell 'dumpsys display|grep mDisplayId=|cut -d "=" -f2|sort -n|uniq|grep -v "^0$"|head -n1')
fi

# use -S if you're edgy
scrcpy --display-id $display -w -S -K &

# ???. Use the this one in case $! doesn't work??
#SCRCPY_PID=$(pgrep scrcpy)
SCRCPY_PID=$!

#
# Payload section starts here
#

# Execute the payload stream generator remotely (with precisely the parameters that it wants)
adb push $PAYLOAD_STORE_DIR/stage1.sh $TARGET_SCRIPT1
adb push $PAYLOAD_STORE_DIR/stage2.sh $TARGET_SCRIPT2
adb shell chmod +x $TARGET_SCRIPT1
adb shell chmod +x $TARGET_SCRIPT2

keep_alive &
KEEP_ALIVE_PID=$!

# Mute the script as it does produce a lot of garbage
adb shell $TARGET_SCRIPT1 $TARGET_FILE $TARGET_CONNECTION_TIMEOUT &> /dev/null &

# Add disclaimer
echo "-----------------------------------------------------"
echo "|                                                   |"
echo "|  Please unlock the phone once the screen appears  |"
echo "|                                                   |"
echo "-----------------------------------------------------"

# Because wait is broken, I'm using this
echo SCRCPY PID: $SCRCPY_PID
tail --pid=$SCRCPY_PID -f /dev/null

kill -9 $KEEP_ALIVE_PID

exit 0