KioskStart.py

#!/usr/bin/env python3
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# This script is used to start the kiosk by configuring sound (if applicable), loading X11 or the user's app, etc.

# Import Python v3.x's type hints as these are used extensively in order to allow MyPy to perform static checks on the code.
from typing import List

import os
import sys
import time

from kiosklib.builder import TextBuilder
from kiosklib.detect import pi_board_get, pulseaudio_soundcards_get
from kiosklib.driver import KioskDriver
from kiosklib.errors import CommandError, KioskError
from kiosklib.invoke import invoke_list_safe, invoke_text, invoke_text_safe, Result
from kiosklib.kiosk import Kiosk
from kiosklib.logger import Logger
from kiosklib.signal import Signal
from kiosklib.various import screen_clear, touchscreens_get


class KioskStart(KioskDriver):
	"""Defines the KioskStart class, which is responsible for starting up the kiosk on every boot after it has been forged."""

	def __init__(self) -> None:
		KioskDriver.__init__(self)

	def _main(self, logger : Logger, origin : str, arguments : List[str]) -> None:
		# Check that we're running on Linux.
		if sys.platform != "linux":
			raise KioskError("This script can only be run on a Linux kiosk machine")

		# Check that we don't have root privileges.
		# pylint: disable-next=no-member
		if os.geteuid() == 0:			# pyrefly: ignore[missing-attribute]
			raise KioskError("You may not be root when running this script")

		# Parse command-line arguments.
		if len(arguments) != 0:						# pylint: disable=duplicate-code
			raise CommandError('"KioskStart.py"')

		# NOTE: We are running in a NON-interactive shell, just in case you need to know (I verified this programatically).

		# Load settings generated by KioskForge on the desktop machine.
		kiosk = Kiosk(self.version)
		kiosk.load_safe(logger, origin + os.sep + "KioskForge.kiosk")

		# Disallow redundant launches of this script (I can't get 'systemd(efunct)' to NOT launch it multiple times).
		signal = Signal("kiosk-running", "kiosk")
		if signal.exists:
			return

		logger.write("Starting kiosk.")
		try:
			# Create the signal that prevents this script from being launched multiple times by systemd.
			signal.create()

			# Configure audio subsystem, if applicable.
			if kiosk.sound_card.data != "none":
				# NOTE: I spent half a night trying out different solutions and none of them worked when done in 'KioskConfig.py',
				# NOTE: so I finally resigned to accepting that 'wpctl' decides how I structure my scripts and put the code here.
				# NOTE: The attempts involved using 'sudo' and lowering privileges to that of the user, none of them worked.
				#if sys.platform == "linux":
				#	# pwd_item = pwd.getpwnam("kiosk")
				#	# NOTE: os.setegid() MUST be called before os.seteuid(), otherwise it raises a PermissionError exception.
				#	#os.setegid(pwd_item.pw_gid)
				#	os.setegid(29) 		# audio group
				#	os.seteuid(pwd_item.pw_uid)
				#	del pwd_item

				# Grab PulseAudio control (pactl) output, keep repeating until we succeed.
				# NOTE: Welcome to systemd...  The PulseAudio server is NOT up when the condition 'After=pipewire.target' is true.
				# NOTE: So we use 1970ish style code, where a little delay is inserted in the code, just to make the turd pretty.
				time.sleep(5)

				# Loop over calling 'wpctl status' until we get meaningful results.
				# NOTE: If the 'time.sleep(5)' above is not present, we simply get an empty list of sinks.  Hooray for systemd!
				# NOTE: The next line is redundant but MyPy doesn't detect that 'result' is always assigned.
				result = Result()
				while True:
					result = invoke_text("pactl list sinks")
					if result.status == 0 and result.output.strip() != "":
						break
					logger.write("Waiting three seconds for 'pactl' to be ready for commands.")
					time.sleep(3)

				# Grab the list of active sinks (typically only one) from the 'wpctl status' output.
				sound_cards = pulseaudio_soundcards_get(result.output)
				del result

				# Make sure we have at least one sink to set the volume of.
				if len(sound_cards) == 0:
					raise KioskError("Unable to detect any PulseAudio sinks")

				# If the sound card is set to 'auto', choose 'usb' then 'jack' for Pi 4B and 'usb' then 'hdmi1' for Pi 5.
				if kiosk.sound_card.data == "auto":
					plug = ""
					if sound_cards.get("usb", ""):
						# Check if there is an USB sound card.  If so, prefer it.
						plug = "usb"
					if not plug:
						# If no USB sound card, use 'jack' on Pi4B and 'hdmi1' on Pi5.
						match pi_board_get():
							case "Pi 4B":
								plug = "jack"
							case "Pi 5":
								plug = "hdmi1"
							case _:
								raise KioskError("Unable to detect model of Raspberry Pi")
					kiosk.assign("sound_card", plug)
					del plug

				found = False
				wanted_card = kiosk.sound_card.data
				for sound_card in sound_cards:
					if sound_card != wanted_card:
						continue

					wanted_id = sound_cards.get(wanted_card, 0)
					if not wanted_id:
						continue

					found = True

					# Select the default sink.
					invoke_text_safe(f"pactl set-default-sink {wanted_id}")

					# Set the audio level of the selected sink to the user-specified percentage on a logarithmic scale.
					invoke_text_safe(f"wpctl set-volume {wanted_id} {kiosk.sound_level.data / 100.0:.2f}")

					del wanted_id

				del sound_cards
				del wanted_card

				if not found:
					logger.error("Unable to locate sound card: " + kiosk.sound_card.data)
					raise KioskError(f"Configuration of sound card '{kiosk.sound_card.data}' failed")
				del found

				# Go back to being root.
				#if sys.platform == "linux":
				#	os.seteuid(0)
				#	os.setegid(0)

			# Auto-configure the 'mouse' option depending on the presence of a touchscreen (present: disable, otherwise: enable).
			if kiosk.mouse.data == "auto":
				touchscreens = touchscreens_get()
				if touchscreens:
					# Disable mouse.
					kiosk.assign("mouse", "false")
				else:
					# Enable mouse.
					kiosk.assign("mouse", "true")
				del touchscreens

			if kiosk.type.data in [ "x11", "web" ]:
				# Move ~/.xsession-errors to ~/.xsession-errors.old to avoid having it grow indefinitely forever.
				if os.path.isfile("/home/kiosk/.xsession-errors"):
					os.replace("/home/kiosk/.xsession-errors", "/home/kiosk/.xsession-errors.old")

				# Only execute the request if $DISPLAY is undefined and $XDG_VTNR is equal to 1 (avoid starting X11 twice).
				if not os.environ.get("DISPLAY") and os.environ.get("XDG_VTNR") == "1":
					# Launch X11, which runs '.config/openbox/autostart', which launches Chromium in kiosk mode or the user app.
					words  = TextBuilder()
					words += "startx"
					if kiosk.mouse.data == "false":
						words += "--"
						words += "-nocursor"
					invoke_list_safe(words.list)
			elif kiosk.type.data == "web-wayland":
				# TODO: Wayland: Support the 'mouse' option (https://gist.github.com/seffs/2395ca640d6d8d8228a19a9995418211).
				if not os.environ.get("WAYLAND_DISPLAY"):
					invoke_text_safe("/usr/bin/dbus-update-activation-environment --systemd WAYLAND_DISPLAY=wayland-0")
					invoke_text_safe("/snap/bin/ubuntu-frame")
					invoke_text_safe(f"/snap/bin/chromium --kiosk '{kiosk.command.data}'")
			elif kiosk.type.data == "cli":
				invoke_text_safe(kiosk.command.data)
			else:
				raise KioskError(f"Unknown kiosk type: {kiosk.type.data}")

			screen_clear()
		finally:
			signal.remove()


if __name__ == "__main__":
	sys.exit(KioskStart().main(sys.argv))