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fix(host): trackpad Y rides the wire in screen convention, flips at the Deck boundary

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Both Deck trackpads were inverted on the virtual pad (first live Deck-to-Deck
session): the client sends SDL's screen-convention coordinates (+y down)
onto the wire, but the Deck's raw report fields are stick convention (+y up)
— and Steam Input parses our report as real Deck hardware — while the host
applier passed the value straight through.

Pin the wire meaning down (quic.rs: TouchpadEx/Touchpad are screen
convention, +x right +y down — what every client capture API produces) and
translate to device-raw in the host applier, the layer that knows the
quirk: steam_proto's apply_rich now negates y (saturating: -32768 has no
i16 negation) for both TouchpadEx surfaces and the DualSense-standin
Touchpad arm, which carried the same latent inversion.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Enrico Bühler
2026-07-08 10:50:30 +02:00
parent b8fd652cb8
commit 9ca672d434
2 changed files with 46 additions and 16 deletions
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crates/punktfunk-host/src/inject/proto/steam_proto.rs
+35 -11
View File
@@ -236,13 +236,23 @@ impl SteamState {
/// wire [`RichInput::Touchpad`] maps to the **right** trackpad (the Deck pad analogous to the
/// DualSense touchpad); the left pad arrives via the M3 `TouchpadEx` surface. [`RichInput::Motion`]
/// passes gyro/accel straight through (raw i16; cross-device unit scaling is M3).
///
/// The wire's touch coordinates are SCREEN convention — +y DOWN, what SDL/Windows/Android
/// capture APIs all produce — but the Deck's raw trackpad fields are stick convention
/// (+y UP, centre origin), and Steam Input parses our report as real Deck hardware. Y is
/// therefore negated here, on the device boundary; leaving it through was the "both
/// trackpads inverted" bug the first live Deck-to-Deck session surfaced (2026-07-08).
pub fn apply_rich(&mut self, rich: RichInput) {
/// Screen-convention (+down) wire Y → Deck raw (+up), saturating (-32768 has no i16 negation).
fn flip_y(y: i16) -> i16 {
(y as i32).saturating_neg().clamp(-32768, 32767) as i16
}
match rich {
RichInput::Touchpad { active, x, y, .. } => {
self.press(btn::RPAD_TOUCH, active);
// Normalized 0..=65535 (centre 32768) → the pad's centred s16 range.
// Normalized 0..=65535 (centre 32768, +y down) → the pad's centred s16 range (+y up).
self.rpad_x = ((x as i32) - 32768) as i16;
self.rpad_y = ((y as i32) - 32768) as i16;
self.rpad_y = (32768 - (y as i32)).min(32767) as i16;
}
RichInput::Motion { gyro, accel, .. } => {
// The wire carries DualSense-convention units (what every client capture emits); the
@@ -259,18 +269,18 @@ impl SteamState {
y,
..
} => {
// Steam pads are natively signed (centre 0), so x/y map straight in. surface 1 =
// Signed centre-0 x maps straight in; y flips to the Deck's +up. surface 1 =
// left pad, anything else (0 single / 2 right) = right pad.
if surface == 1 {
self.press(btn::LPAD_TOUCH, touch);
self.press(btn::LPAD_CLICK, click);
self.lpad_x = x;
self.lpad_y = y;
self.lpad_y = flip_y(y);
} else {
self.press(btn::RPAD_TOUCH, touch);
self.press(btn::RPAD_CLICK, click);
self.rpad_x = x;
self.rpad_y = y;
self.rpad_y = flip_y(y);
}
}
}
@@ -557,9 +567,9 @@ mod tests {
});
assert_ne!(s.buttons & btn::RPAD_TOUCH, 0);
assert_eq!(s.rpad_x, 32767); // 65535-32768
assert_eq!(s.rpad_y, -32768); // 0-32768
// Motion is rescaled from the wire (DualSense) convention into Deck units (gyro ×16/20,
// accel ×16384/10000) — see steam_remap::motion_wire_to_deck.
assert_eq!(s.rpad_y, 32767); // wire y=0 = TOP (screen conv) → Deck raw +up (clamped)
// Motion is rescaled from the wire (DualSense) convention into Deck units (gyro ×16/20,
// accel ×16384/10000) — see steam_remap::motion_wire_to_deck.
s.apply_rich(RichInput::Motion {
pad: 0,
gyro: [1000, -2000, 0],
@@ -570,7 +580,8 @@ mod tests {
}
/// M3: the wire back-button bits map to the four Deck grips + QAM, and `TouchpadEx` routes the
/// left / right surfaces to the matching pad (signed coords pass straight through).
/// left / right surfaces to the matching pad (x passes straight through; y flips from the
/// wire's screen convention (+down) to the Deck's raw +up — the live-verified direction).
#[test]
fn back_buttons_and_dual_trackpad_mapping() {
let s = SteamState::from_gamepad(
@@ -601,7 +612,7 @@ mod tests {
});
assert_ne!(s.buttons & btn::LPAD_TOUCH, 0);
assert_ne!(s.buttons & btn::LPAD_CLICK, 0);
assert_eq!((s.lpad_x, s.lpad_y), (-5000, 6000));
assert_eq!((s.lpad_x, s.lpad_y), (-5000, -6000));
s.apply_rich(RichInput::TouchpadEx {
pad: 0,
surface: 2,
@@ -613,7 +624,20 @@ mod tests {
pressure: 0,
});
assert_ne!(s.buttons & btn::RPAD_TOUCH, 0);
assert_eq!((s.rpad_x, s.rpad_y), (7000, -8000));
assert_eq!((s.rpad_x, s.rpad_y), (7000, 8000));
// The i16 edge: wire y = -32768 (top-most) must clamp, not overflow.
s.apply_rich(RichInput::TouchpadEx {
pad: 0,
surface: 2,
finger: 0,
touch: true,
click: false,
x: 0,
y: -32768,
pressure: 0,
});
assert_eq!(s.rpad_y, 32767);
}
/// The serial reply carries the leading report-id byte the kernel strips, so the *stripped*