Sylpheed/port/scripts/gamepad.gd

class_name Gamepad
extends RefCounted

## The physical controller: the two buttons Godot does not bind, and the one
## input that is not an edge.
##
## 🔴 BOTH DEFECTS WERE REPORTED BY A HUMAN PLAYING THE PORT (2026-09-01), and
## neither could have been caught by the `--script` harness, because that harness
## sends `InputEventAction` — which bypasses the input map and is not an analog
## axis. The unattended P5 walk passed on every iteration while Ⓐ did nothing at
## all on a real pad. **A synthetic-input test asserts the code after the input
## map, never the input map itself.**
##
## ## 1. Godot 4.7.2 binds no joypad button to `ui_accept` or `ui_cancel`
##
## Measured on this exact build rather than remembered, because the answer has
## changed between Godot versions and the remembered one was wrong:
##
## ```
## ui_accept   key:Enter, key:Kp Enter, key:Space          <- no joypad at all
## ui_cancel   key:Escape                                  <- no joypad at all
## ui_up       key:Up, JOYBTN:11, JOYAXIS:1-               <- d-pad AND left stick
## ui_down     key:Down, JOYBTN:12, JOYAXIS:1+
## ui_left     key:Left, JOYBTN:13, JOYAXIS:0-
## ui_right    key:Right, JOYBTN:14, JOYAXIS:0+
## ```
##
## That asymmetry is the whole bug report: navigation worked on the pad and Ⓐ/Ⓑ
## did nothing, which reads like a broken controller and is a complete input map
## for four actions out of six.
##
## The events are **added to** the built-in actions, never redefined. Declaring
## `ui_accept` in `project.godot` replaces the built-in wholesale, so the
## keyboard bindings would have to be restated there and would silently rot the
## next time Godot changes them.
##
## ## 2. A stick is not a button
##
## `ui_up`/`ui_down` are bound to **axis 1**, so the left stick navigates — which
## is correct, the real game accepts it too. But an axis emits a fresh
## `InputEventJoypadMotion` every time the value *changes*, and a real stick held
## at deflection jitters continuously. Every one of those events reports the
## action as pressed, so a held stick was one cursor step per jitter: the human's
## words were "moves the cursor too fast", and on a five-item menu it crosses
## faster than the eye follows.
##
## So the stick is **latched**: it fires once when it leaves the neutral zone and
## not again until it comes back. That makes it behave exactly like the d-pad,
## which needs no latch because a button already is an edge.
##
## ⚠️ ~~AUTHORED, NOT MEASURED — and deliberately the conservative half.~~
## 🔴 **THE GAME DOES REPEAT, and this paragraph predicted its own refutation.**
## It said: *"If the game does repeat, this is a difference a human will notice
## as 'I have to flick it again'."* On 2026-09-02 a human who has played both
## reported exactly that — *"holding only moves one item. In game it actually
## continues to move when holding up/down, just at a medium pace"*.
##
## So one-step-per-deflection is no longer the conservative reading; it is a
## known defect. The mechanism is implemented below and the **rate is not
## shipped** — see `REPEAT_DELAY` for why an approximate one is worse than none.

## ✅ DECODED 2026-09-01, and it replaces an authored value.
##
## This was **0.5**, chosen as a *floor* rather than as a value: Godot's action
## deadzone for the `ui_*` actions is 0.50, so the latch must not arm below it —
## the action itself would not read as pressed and the step would be swallowed
## anyway, leaving the latch armed against a press that never happened. That
## reasoning still holds and 0.61 is comfortably above the floor.
##
## The game's own threshold is now measured: it **digitises the left stick to
## four direction bits at 61 % deflection**, so it never sees a velocity at all
## (`docs/re/input-button-numbering-is-remapped.md` and the corrected
## `input-pad-read-path.md`). Between 0.50 and 0.61 Godot reports `ui_down`
## pressed and the real game reports nothing; at 0.5 this port stepped there.
##
## 📌 The mechanism also corroborates the human's fix rather than merely
## agreeing with it: a control that digitises to bits cannot express a rate, so
## "one step per deflection" is what the hardware layer *can* produce, not a
## conservative guess that happened to look right.
##
## ⚠️ **The 0.11 gap to `RELEASE` stays AUTHORED.** Nothing measured says the
## game has hysteresis at all, let alone how wide. Only the arm threshold moved.
##
## 🔴 **This changes how the stick feels and a human chose the old number.**
## Asserted at the device level below and in `tools/port/verify-input`, but a
## feel-test is the real check: revert this one constant to 0.5 if 0.61 reads as
## a stick that needs pushing too far.
const ENTER := 0.61

## Release lower than it arms. Without the gap a stick resting near 0.5 chatters
## across the boundary and re-arms on noise, which is the original bug wearing a
## smaller number.
const RELEASE := 0.4

## ## 3. A held direction repeats — MECHANISM PRESENT, RATE NOT SHIPPED
##
## A human who has played both reported it on 2026-09-02: *"holding only moves
## one item. In game it actually continues to move when holding up/down, just at
## a medium pace"*, and separately *"Confirmed D-Pad does repeat when holding
## too."* So the FACT covers both input devices, which is why `held_direction()`
## polls the pad and the keyboard and not just the stick.
##
## 🔴 **THE RATE IS DELIBERATELY UNSET, AND THE REPEAT DOES NOT RUN UNTIL IT IS
## MEASURED.** The instruction is explicit: *"Take the RATE from the Decoder — do
## NOT ship a placeholder interval. An invented rate here is indistinguishable
## from a measured one later, and this is the exact field where that already cost
## us."*
##
## An earlier draft of this file had 0.40 / 0.20 with a paragraph explaining that
## they were authored. **That is precisely the failure mode named above** — the
## explanation would have been merged, the numbers would have felt roughly right,
## and nothing afterwards could distinguish them from a measurement. They are
## removed rather than commented out.
##
## 📌 **A constant interval is the right SHAPE, and that part IS measured.** The
## game digitises the left stick to four direction bits at 61 % deflection
## (`ENTER` above), so it cannot see deflection magnitude at all — a repeat it
## drives cannot be faster-the-harder-you-push. That excludes the one competing
## model, so only the two constants are open, and one measurement closes both.
##
## ⚠️ **TO ADOPT, TWO THINGS CHANGE, NOT ONE.** Set both constants to the
## measured seconds — and update `tools/port/verify-input`, whose row *"a held
## stick is ONE step, not six"* currently asserts **the absence of this
## feature**. It passes today because the repeat is inert; the moment a rate is
## adopted a held stick SHOULD produce further steps, and that green row would
## go red for the right reason and be read as a regression.
##
## 📌 That row is not wrong. A check written against today's behaviour becomes an
## assertion that the behaviour never changes, and this one has the additional
## trap of looking like a bug-fix regression test — it was written for the
## jitter defect, and the repeat is not that defect returning.
## `pad-repeat` in `BLOCKED.md` carries the request.
const REPEAT_DELAY := -1.0
const REPEAT_INTERVAL := -1.0


## Whether a measured repeat rate has been adopted. Until it has, the port keeps
## its current one-step-per-deflection behaviour, which is KNOWN WRONG but is
## wrong in a way nobody will mistake for a measurement.
static func repeat_rate_known() -> bool:
	return REPEAT_DELAY > 0.0 and REPEAT_INTERVAL > 0.0

## Only the left stick. The triggers are axes too, and latching them here would
## silently swallow input the port does not read yet but might.
const STICK := [JOY_AXIS_LEFT_X, JOY_AXIS_LEFT_Y]

var _latched: Dictionary = {}
var _repeat_direction := 0
var _repeat_clock := 0.0


## Add the joypad buttons the built-in map omits. Returns a human-readable line,
## or "" if nothing needed adding — so a future Godot that ships these bindings
## makes this quietly stop reporting rather than double-binding.
static func bind_missing() -> String:
	var added := PackedStringArray()
	for pair in [["ui_accept", JOY_BUTTON_A, "Ⓐ"], ["ui_cancel", JOY_BUTTON_B, "Ⓑ"]]:
		var action: String = pair[0]
		var button: int = pair[1]
		if not InputMap.has_action(action):
			# Not a warning we can act on, but silence here would present as the
			# original bug and send the next person back to the controller.
			push_warning("gamepad: no such action %s -- pad button unbound" % action)
			continue
		if _has_button(action, button):
			continue
		var ev := InputEventJoypadButton.new()
		ev.button_index = button
		InputMap.action_add_event(action, ev)
		added.append("%s -> %s" % [pair[2], action])
	if added.is_empty():
		return ""
	return "pad:   bound %s (Godot 4.7.2 binds no joypad button to either)" % \
		", ".join(added)


static func _has_button(action: String, button: int) -> bool:
	for e in InputMap.action_get_events(action):
		if e is InputEventJoypadButton and e.button_index == button:
			return true
	return false


## True if this event should be acted on. Everything that is already an edge —
## keys, d-pad, mouse — passes straight through; only the analog stick is
## latched, and only on the two axes the navigation actions are bound to.
func accepts(event: InputEvent) -> bool:
	if not (event is InputEventJoypadMotion):
		return true
	var axis: int = event.axis
	if not STICK.has(axis):
		return true
	var value: float = event.axis_value
	var direction := 0
	if value >= ENTER:
		direction = 1
	elif value <= -ENTER:
		direction = -1

	if direction == 0:
		# Neutral enough to re-arm? The gap between RELEASE and ENTER is the
		# hysteresis band: inside it the stick is neither a new press nor
		# released, so the latch is left exactly as it was.
		if absf(value) <= RELEASE:
			_latched[axis] = 0
		return false
	if int(_latched.get(axis, 0)) == direction:
		return false  # still held in the same direction: not a new press
	_latched[axis] = direction
	return true


## Which way a direction is being HELD right now, as -1 (up), 0 or +1 (down).
##
## 🔴 **Polled at the DEVICE, never through `Input.is_action_pressed`.** `ui_up`
## and `ui_down` are bound to the stick axis at Godot's 0.50 action deadzone,
## while this port steps at the game's measured 0.61. Polling the action would
## repeat throughout the 0.50–0.61 band — the exact band `ENTER` exists to
## exclude — so the repeat would contradict the threshold on the same stick.
## That is the input-map lesson again: assert the device, not the layer above it.
func held_direction() -> int:
	# The stick, from the latch `accepts()` already maintains, so the repeat and
	# the first step read one state and cannot disagree about hysteresis.
	var stick := int(_latched.get(JOY_AXIS_LEFT_Y, 0))
	if stick != 0:
		return stick
	for device in Input.get_connected_joypads():
		if Input.is_joy_button_pressed(device, JOY_BUTTON_DPAD_UP):
			return -1
		if Input.is_joy_button_pressed(device, JOY_BUTTON_DPAD_DOWN):
			return 1
	if Input.is_key_pressed(KEY_UP):
		return -1
	if Input.is_key_pressed(KEY_DOWN):
		return 1
	return 0


## One repeat step, or 0. Call once per frame with the frame's delta.
##
## The FIRST step is not this function's: it comes from the event edge in
## `_unhandled_input`, and the clock below starts from that same frame, so a held
## direction gives one step now and the next only after `REPEAT_DELAY`. A change
## of direction restarts the delay rather than inheriting the old cadence.
func repeat_due(delta: float) -> int:
	if not repeat_rate_known():
		return 0
	var direction := held_direction()
	if direction == 0 or direction != _repeat_direction:
		_repeat_direction = direction
		_repeat_clock = 0.0
		return 0
	_repeat_clock += delta
	if _repeat_clock < REPEAT_DELAY:
		return 0
	# Subtract rather than reset, so the cadence cannot drift with the frame rate
	# -- at 140 fps and at 30 fps the same number of steps happen per second.
	_repeat_clock -= REPEAT_INTERVAL
	return direction


## The pads Godot can see, for the startup line. A run where the human believes
## a controller is connected and Godot disagrees should say so on its own,
## rather than presenting as unresponsive buttons.
static func report_devices() -> String:
	var pads := Input.get_connected_joypads()
	if pads.is_empty():
		return "pad:   none connected -- keyboard only (Enter/Space = Ⓐ, Escape = Ⓑ)"
	var names := PackedStringArray()
	for j in pads:
		names.append("[%d] %s" % [j, Input.get_joy_name(j)])
	return "pad:   " + ", ".join(names)