Sylpheed/docs/port/held-direction-repeat.md

# F1 — the menu repeats on a held direction: mechanism shipped, **and the rate adopted**

**Status:** ✅ mechanism implemented and wired, 2026-09-02. ✅ **rate adopted
2026-09-13** from `docs/re/f1-repeat-measured-via-driver-patch.md` —
`REPEAT_DELAY = 0.402`, `REPEAT_INTERVAL = 0.134`. It ran inert for eleven days
and that was the right state; this page keeps the inert-era reasoning because it
is why the two numbers can be trusted now.

## What was reported

Two statements from the human, both about the **real game**, a play-test apart:

> *"Moving stick up/down and holding only moves one item. In game it actually
> continues to move when holding up/down, just at a medium pace so player does
> not need to move pad middle↔up/down, but also slow enough to see which item is
> selected and move to target."*

> *"Confirmed D-Pad does repeat when holding too."*

## The file predicted its own refutation

`gamepad.gd` carried this, written when the latch was added:

> *"Whether the real game repeats while a direction is held, and how fast, is
> unknown… If the game does repeat, this is a difference a human will notice as
> 'I have to flick it again', and the fix is a measured repeat interval — not a
> guessed one."*

That is exactly what happened, in the words it predicted. **So
one-step-per-deflection is no longer the conservative reading — it is a known
defect**, and keeping it is choosing a wrong behaviour over an approximate one.

## What was built

| | |
|---|---|
| `Gamepad.held_direction()` | −1 / 0 / +1, polled from the **devices** |
| `Gamepad.repeat_due(delta)` | one step or 0, per frame |
| `Boot._menu_repeat(delta)` | calls it under the same guards a real press gets |

### Why it polls devices and not `Input.is_action_pressed`

`ui_up`/`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** (`ENTER`).
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, on the same frame.

That is the input-map lesson from 2026-09-01 arriving in a new place: **assert
the device, not the layer above it.** The stick reads from the latch
`accepts()` already maintains, so the first step and the repeat cannot disagree
about hysteresis; the d-pad reads `JOY_BUTTON_DPAD_UP/DOWN` directly, which the
human's second report makes load-bearing rather than defensive.

### Why the guards are duplicated rather than shared

`_menu_repeat` re-applies the same four conditions `_unhandled_input` applies —
no movie playing, a menu exists, its stack is non-empty, no transition pending.
A repeat that could fire during a movie or mid-transition would be a **second,
subtly different input path**, and the first thing this port learned about input
is that a second path is where the defect hides.

## ✅ The rate, and how far each half of it reaches

An earlier draft had `REPEAT_DELAY = 0.40` and `REPEAT_INTERVAL = 0.20` with a
paragraph explaining that they were authored. They were removed rather than
commented out, on an explicit instruction:

> *"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."*

📌 **The measurement has now landed, and it vindicates the instruction in the
most awkward possible way: the guessed delay was nearly right and the guessed
interval was off by 50 %.** 0.40 against a measured 0.402; 0.20 against a
measured 0.134. Had both shipped, the half that was wrong would have been
protected by the half that was right.

The Decoder measured, in Canary at an achieved 29.87 fps guest rate, **12 frames**
from the press-triggered step to the first repeat and **4 frames** per step after
it. Converted to seconds here because this port does not run at the guest's rate
and it is the cadence that was measured: 12 / 29.87 = **0.402**, 4 / 29.87 =
**0.134**.

### ⚠️ The two numbers are not equally well evidenced

No physical controller exists in the Decoder's container. The measurement was
taken by patching Canary's `--hid=file` driver to emit Keystroke `REPEAT` at the
**SDL driver's own** 400 ms / 100 ms constants:

* the **delay** came back as 402 ms — to within the frame quantum, *the constant
  that was fed in*. It confirms the instrument, not the game;
* the **interval** came back as 133 ms against a fed-in 100 ms. That gap is the
  genuinely new fact: the game paces repeats to its own frame consumption rather
  than to the event stream.

So the interval is what the game does; the delay is what Xenia's SDL driver does,
and the game was not observed to disagree. **One run** — the corpus's own two-run
minimum is not met, and the source page says so itself.

**One thing about the rate was already measured, and it narrowed the question.**
The game digitises the left stick to four direction bits at 61 % deflection, so
it cannot see deflection magnitude at all — the repeat it drives *cannot* be
faster-the-harder-you-push. That excluded the one competing model, so only two
constants were ever open and a single measurement closed both.

## 🔴 Adopting the rate was predicted to break a green check. It did not, and that was worse

This page and `gamepad.gd` both said that `verify-input`'s row *"a held stick is
ONE step, not six"* asserts the **absence** of the repeat, and would go red on
adoption — looking like the 2026-09-01 jitter defect returning.

**Run on adoption day: the row stayed green.** `steps()` feeds axis values through
the latch and never advances a clock, so it had never called `repeat_due()` at
all. The row tests the *latch*, which the repeat does not touch. The prediction
was reasoned rather than run.

What it hid is the real problem: the rate was about to ship into a harness with
**no coverage of this feature whatsoever**, and that green line would have been
read as coverage of it.

The fix was not to change that row. `verify-input` gains a `repeat` subject that
holds a direction through the same latch and ticks `repeat_due()`, asserting
**these two numbers** — a shape-only check ("it repeats eventually") would have
passed on the 0.40 / 0.20 guess this port refused to ship. Five rows: nothing
before the delay, the first repeat on the delay, the steady interval, cadence
independent of frame rate (the code claims this in a comment, so it is asserted),
and a direction change restarting the delay.

⚠️ **The origin is one frame, and it is not a tolerance.** `repeat_due()`'s first
call only latches the direction; the clock accumulates from the call after it. In
the port that first call is the frame the press is handled — the frame that
produced the press-triggered step — which is the origin the finding measures its
12 frames from. Measured from `t = 0` the harness read 0.433 against 0.402 and
the tolerance would have had to be widened to hide a units mismatch.

## What this does not claim

* That the repeat feels right. It runs now, and **only a human can answer that**:
  0.134 s is ~7.5 steps a second, and the play-test that opened this asked for
  *"slow enough to see which item is selected"*. If it reads as too fast, the
  100 ms constant is Xenia's and not the game's, and no capture in that
  container would have revealed it.
* Any rate, or any bound on one. "Medium pace" is a direction, not a number, and
  it is not recorded anywhere as data.
* That the d-pad and the stick repeat at the *same* rate. Both repeat; nobody
  has said they match, and the code currently assumes one rate for both.