Swipe this controller (please)

If you want touch controls to map to standard input actions, steal the code from below.

Backstory

I was paying my tutorial tithe (give help 10x the number of times you ask for help) and some brilliant people I respect pointed out that Godot 4 is still gently broken with respect to swipes.

In general UI is hard, so this isn’t criticism.

I thought of a “yes and”, and then decided it’d be too weird to necro the thread to post it, so I’m posting it here for posterity.

NODED tie in!

I want my horror game on tablet ideally. And I have at least two modes of input (longpress the omen to indicate it’s wrong, but also some mechanism of scrolling around the world). The former is a tap and the latter is a swipe. I might get really fancy and do multifinger gestures. But anyway, being able to map complex user gestures back into simple command inputs would be very nice.

And in fact I already do this! The user’s keyboard input is mapped into minimap movement. The minimap movement triggers various areas on the minimap and they inject camera movement events (which isn’t directly the same as the user’s input – the camera is moving 6dof while the user only controls WASD).

So! Here’s the code.

Godot’s input

# Turns screen events into real actions.
# Put me in the scene that wants it, or into an autoload if you like to live dangerously.
# I use `unhandled_input` so that e.g. drag handlers can grab my event away from me.
extends Node

# In standard `Input.get_vector` order.
@export var actions: Array[StringName] = [&"ui_left", &"ui_right", &"ui_up", &"ui_down"]
const directions: Array[Vector2] = [Vector2.LEFT, Vector2.RIGHT, Vector2.UP, Vector2.DOWN]

# If you cover 1/64th of the screen in one gesture, you're outputting max strength controls. Less? Less.
# Probably there should be some sensitivity here.
# You could also imagine an onscreen joystick, using displacement from a fixed point rather than relative swipes.
# You could imagine buffering the input so you can smooth the touch (acceleration, etc).
# But this is what the specific user wanted.
# I have not tuned this param at all.
@export var max_speed_as_frac_of_screen := 1.0 / 64 * Vector2.ONE

func _unhandled_input(e: InputEvent):
  if e is InputEventScreenDrag:
    # Could cache this value and only recalc on window resize.
    # Assumes we are under root, not a subviewport.
    var pixels_for_one := get_viewport().size * max_speed_as_frac_of_screen as Vector2
    var scaled := e.screen_velocity / pixels_for_one
    for i in directions.size():
      var event := InputEventAction.new()
      event.action = actions[i]
      event.strength = clampf(directions[i] * scaled, 0, 1)
      event.pressed = !!event.strength  # 0.0 is false, which the clampf ensures is slightly likely.
      Input.parse_input_event(event)