Fix false positives in Godot joypad device detection (e.g. touchpads). See https://github.com/godotengine/godot/issues/59250#issuecomment-1786196830

NonJoypads.gd

# Public domain, as per The Unlicense. NO WARRANTY. See https://unlicense.org

extends Node
## Solves a [url=https://github.com/godotengine/godot/issues/59250]bug[/url] where touchpad devices
## can be detected as a joypad.
##
## This script should be autoloaded in the project settings.
## This is merely a workaround, not intended for use in production code.

func _enter_tree() -> void:
	_connect_joy_check()
	queue_free()

static func _connect_joy_check() -> void:
	var _Self: GDScript = (func() -> void:).get_object() as GDScript
	if Input.joy_connection_changed.connect(Callable(_Self, joy_check.get_method())) != OK:
		assert(false)
	pass

## Validates a joypad connection. Called for every joypad device connected.
## Device names matching the pattern will be disabled (remapped to an empty mapping).
static func joy_check(device: int, connected: bool) -> void:
	if not connected:
		return
	var device_name: String = Input.get_joy_name(device)
	# Uncomment the line below to debug problematic devices:
	# print('Connected device ', device, ': ', device_name)
	if not is_banned(device_name):
		return
	# If name has matched any banned word, this joypad device should be ignored.
	var guid: String = Input.get_joy_guid(device)
	# Disable input by mapping no axes or buttons. Will ignore future joypad input from this device.
	var mapping: String = guid + ',' + device_name.replace(',', '')
	Input.add_joy_mapping(mapping, true)
	# Past input events might have been sent. Reset this device sending 0 on all SDL axes and buttons.
	for axis: JoyAxis in range(JOY_AXIS_SDL_MAX) as Array[JoyAxis]:
		var event: InputEventJoypadMotion = InputEventJoypadMotion.new()
		event.device = device
		event.axis = axis
		Input.parse_input_event(event)
	for button_index: JoyButton in range(JOY_BUTTON_SDL_MAX) as Array[JoyButton]:
		var event: InputEventJoypadButton = InputEventJoypadButton.new()
		event.device = device
		event.button_index = button_index
		Input.parse_input_event(event)
	prints('Ignoring joypad device:', mapping) # you can comment out or remove this line

## True only if the device name contains a banned word, case-insensitively.
## A banned substring only matches if it's guaranteed to be a separate word.
static func is_banned(device_name: String) -> bool:
	for word: String in banned_words:
		var i: int = device_name.findn(word)
		if i < 0:
			continue # this banned word was not found as a substring
		if i > 0 and not is_ascii_non_letter(device_name[i - 1]):
			continue # substring found, but it's not guaranteed to start a word
		var j: int = i + word.length()
		if j < device_name.length() and not is_ascii_non_letter(device_name[j]):
			continue # it starts a word, but it's not guaranteed to also end it
		return true # substring found and guaranteed to form a separate word
	return false # no banned word found

## True only if the character is ASCII and not a letter.
static func is_ascii_non_letter(c: String) -> bool:
	return c.unicode_at(0) < 128 and not (c >= 'a' and c <= 'z' or c >= 'A' and c <= 'Z')

## List of words forbidden in joypad names.
const banned_words: PackedStringArray = [
	'touchpad', 'trackpad', 'clickpad', 'synaptics',
	'mouse',
	'pen', 'finger', # drawing tablets
	'keyboard',
	'led',
]

Revised to match the PR godotengine/godot#101260, see also godotengine/godot#59250 (comment)
Adding synaptics as a banned word, since the device name no longer includes "touchpad" after a system update on Linux.

Are you using Linux? A recent (kernel?) update changed the name on the touchpad device in my laptop. [...]
For me, the device name was SynPS/2 Synaptics TouchPad, but became Synaptics TM2768-001.