fix(input): Nintendo A/B face map on NX

SDL labels south as a and east as b; on Switch remap so physical A
confirms and physical B cancels in launcher and NamingScreen.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/switch-development.md

@@ -217,14 +217,16 @@ Measured on Switch OLED (`feat/switch-nx`, love-nx `11.5-nx1`, 1280×720). Both
 
 | Path | Control | Mapping |
 | ---- | ------- | ------- |
-| `gamepadpressed` | D-pad / left stick | move (via `GamepadMap.DEFAULT_GAMEPAD_BINDINGS`) |
-| `gamepadpressed` | `a` / `b` (SDL) | GB A / B — physical **B** (south) confirms, physical **A** (east) cancels |
+| `gamepadpressed` | D-pad / left stick | move |
+| `gamepadpressed` | SDL `a` / `b` on **NX** | swapped via `NX_GAMEPAD_BINDINGS`: physical **A** (east) = GB A confirm, physical **B** (south) = GB B cancel |
+| `gamepadpressed` | SDL `a` / `b` on desktop | identity (SDL south = GB A) |
 | `gamepadpressed` | `start` / `back` | Start / Select |
 | `joystickpressed` (raw) | only if **not** `isGamepad()` | face/menu fallback |
-| `joystickpressed` (raw) | `#1` / `#2` | GB A / B |
-| `joystickpressed` (raw) | `#3` Y / `#4` X | GB A / B (OLED naming diagnosis) |
+| `joystickpressed` (raw) | `#1` / `#2` on NX | Nintendo B / A → GB B / A |
 | `joystickpressed` (raw) | `#9` / `#10` | Select / Start (− / +) |
 
+**Nintendo UX on Switch:** physical A confirms, physical B cancels (explicit NX remap of SDL face labels).
+
 **Dual-path rule:** love-nx emits both `gamepadpressed` and `joystickpressed` for Joy-Con. When `joystick:isGamepad()` is true, Input and RomImporter **ignore raw** face/menu so NamingScreen does not see A+B in one frame. `NamingScreen` also prefers A over B if both edges still fire.
 
 Implementation: `src/core/GamepadMap.lua` (`NX_RAW_*`, `ignoreRawForJoystick`). Launcher and gameplay share the same converter.

src/core/GamepadMap.lua

@@ -3,42 +3,48 @@
 
 local GamepadMap = {}
 
--- LÖVE SDL game-controller mapping (D-pad / face / menu).
+-- LÖVE SDL game-controller mapping (D-pad / face / menu) — desktop/mobile.
 GamepadMap.DEFAULT_GAMEPAD_BINDINGS = {
   dpup = "up", dpdown = "down", dpleft = "left", dpright = "right",
   a = "a", b = "b",
   start = "start", back = "select",
 }
 
+-- Switch: LÖVE/SDL labels south as "a" and east as "b", but Nintendo UX is
+-- physical A (east) = confirm (GB A), physical B (south) = cancel (GB B).
+GamepadMap.NX_GAMEPAD_BINDINGS = {
+  dpup = "up", dpdown = "down", dpleft = "left", dpright = "right",
+  a = "b", -- SDL south = Nintendo B → GB B
+  b = "a", -- SDL east = Nintendo A → GB A
+  start = "start", back = "select",
+}
+
 -- Generic SDL joysticks without a game-controller DB entry (Linux handhelds).
 GamepadMap.RAW_BUTTON_BINDINGS = {
   [1] = "a", [2] = "b",
   [7] = "select", [8] = "start", [9] = "select", [10] = "start",
 }
 
--- Switch OLED: love.joystickpressed indices (1-based). Used only when the
--- device is NOT a gamepad — love-nx also emits gamepadpressed for Joy-Con,
--- and applying both face paths in one frame breaks NamingScreen (a+b).
--- Y→a / X→b matches operator OLED naming diagnosis (2026-08-01).
+-- Switch OLED raw indices (1-based). Only when NOT isGamepad() — love-nx
+-- also emits gamepadpressed; dual-path face presses break NamingScreen.
+-- #1 = Nintendo B, #2 = Nintendo A (probe); Y/X left unmapped for naming.
 GamepadMap.NX_RAW_BUTTON_BINDINGS = {
-  [1] = "a", [2] = "b",
-  [3] = "a", [4] = "b",
+  [1] = "b", [2] = "a",
   [9] = "select", [10] = "start",
 }
 
--- Raw index -> gamepad button name for RomImporter routing.
+-- Raw index -> gamepad button *name* for RomImporter (then NX face swap applies).
 GamepadMap.RAW_TO_GAMEPAD_BUTTON = {
   [1] = "a", [2] = "b",
   [7] = "back", [8] = "start", [9] = "back", [10] = "start",
 }
 
 GamepadMap.NX_RAW_TO_GAMEPAD_BUTTON = {
-  [1] = "a", [2] = "b",
-  [3] = "a", [4] = "b",
+  [1] = "a", [2] = "b", -- SDL south/east names; NX_GAMEPAD_BINDINGS swaps to GB
   [9] = "back", [10] = "start",
 }
 
--- Test hook: force NX raw tables without stubbing love.
+-- Test hook: force NX tables without stubbing love.
 GamepadMap._forceNXForTests = false
 
 function GamepadMap._setForceNXForTests(v)
@@ -52,8 +58,13 @@ local function nxActive()
   return false
 end
 
+function GamepadMap.gamepadBindings()
+  if nxActive() then return GamepadMap.NX_GAMEPAD_BINDINGS end
+  return GamepadMap.DEFAULT_GAMEPAD_BINDINGS
+end
+
 function GamepadMap.mapGamepadButton(button)
-  return GamepadMap.DEFAULT_GAMEPAD_BINDINGS[button]
+  return GamepadMap.gamepadBindings()[button]
 end
 
 -- love-nx / SDL: when isGamepad(), face+menu already arrive via gamepad*.

src/core/Input.lua

@@ -51,7 +51,7 @@ end
 function Input:applyBindings(overlay)
   local keys, pads = {}, {}
   for key, action in pairs(DEFAULT_BINDINGS) do keys[key] = action end
-  for button, action in pairs(GamepadMap.DEFAULT_GAMEPAD_BINDINGS) do
+  for button, action in pairs(GamepadMap.gamepadBindings()) do
     pads[button] = action
   end
   for actionId, binding in pairs(overlay or {}) do

src/import/RomImporter.lua

@@ -1513,7 +1513,9 @@ end
 
 function RomImporter:gamepadpressed(_, button)
   self:_activatePadCursor()
-  if button == "a" then
+  -- Map through GamepadMap so NX swaps SDL face labels to Nintendo A/B.
+  local action = GamepadMap.mapGamepadButton(button)
+  if action == "a" then
     -- Instant click at the virtual pointer (same path as a mouse/touch tap).
     self:mousepressed(self._padCursor.x, self._padCursor.y, 1)
   elseif button == "leftshoulder" then

tests/engine/input_dual_path_test.lua

@@ -1,4 +1,5 @@
 -- When isGamepad(), raw face presses must not stack on gamepad* (NamingScreen a+b).
+-- On NX, SDL face labels are swapped so physical A confirms / B cancels.
 package.path = "./?.lua;./?/init.lua;" .. package.path
 if not _G.love then _G.love = require("tests.love_stub") end
 
@@ -20,23 +21,40 @@ check(GamepadMap.ignoreRawForJoystick(gamepadJoy), "ignore raw when isGamepad")
 check(not GamepadMap.ignoreRawForJoystick(rawJoy), "allow raw when not gamepad")
 check(not GamepadMap.ignoreRawForJoystick(nil), "nil joystick does not ignore raw")
 
+-- Desktop: SDL a → GB A (unchanged).
+eq(GamepadMap.mapGamepadButton("a"), "a", "desktop SDL a -> GB A")
+eq(GamepadMap.mapGamepadButton("b"), "b", "desktop SDL b -> GB B")
+
 GamepadMap._setForceNXForTests(true)
-eq(GamepadMap.mapRawButton(3), "a", "NX raw Y (#3) -> GB A")
-eq(GamepadMap.mapRawButton(4), "b", "NX raw X (#4) -> GB B")
+eq(GamepadMap.mapGamepadButton("a"), "b", "NX SDL south (a) -> GB B (Nintendo B)")
+eq(GamepadMap.mapGamepadButton("b"), "a", "NX SDL east (b) -> GB A (Nintendo A)")
+eq(GamepadMap.mapRawButton(1), "b", "NX raw #1 Nintendo B -> GB B")
+eq(GamepadMap.mapRawButton(2), "a", "NX raw #2 Nintendo A -> GB A")
+eq(GamepadMap.mapRawButton(3), nil, "NX raw Y (#3) not mapped as confirm")
+eq(GamepadMap.mapRawButton(4), nil, "NX raw X (#4) not mapped as confirm")
 GamepadMap._setForceNXForTests(false)
 
 Input:init()
 Input:gamepadpressed(gamepadJoy, "a")
 Input:joystickpressed(gamepadJoy, 1) -- must no-op
-Input:joystickpressed(gamepadJoy, 2) -- must no-op (would have set b)
+Input:joystickpressed(gamepadJoy, 2) -- must no-op
 Input:step()
-check(Input:wasPressed("a"), "gamepad A edge present")
+check(Input:wasPressed("a"), "desktop gamepad A edge present")
 check(not Input:wasPressed("b"), "raw must not add B alongside gamepad A")
 check(Input:isDown("a"), "A held from pad source only")
 
+-- NX: physical A arrives as SDL "b" → GB A.
+GamepadMap._setForceNXForTests(true)
+Input:init()
+Input:gamepadpressed(gamepadJoy, "b")
+Input:step()
+check(Input:wasPressed("a"), "NX physical A (SDL b) confirms as GB A")
+check(not Input:wasPressed("b"), "NX physical A must not also erase")
+GamepadMap._setForceNXForTests(false)
+
 Input:init()
 Input:joystickpressed(rawJoy, 1)
 Input:step()
-check(Input:wasPressed("a"), "non-gamepad raw #1 still maps to A")
+check(Input:wasPressed("a"), "non-gamepad raw #1 still maps to A on desktop")
 
 T.finish()

tests/engine/input_nx_raw_map_test.lua

@@ -1,4 +1,4 @@
--- NX raw fallback indices measured on OLED hardware (SWNX-11).
+-- NX raw fallback + Nintendo face remap (SWNX-11).
 package.path = "./?.lua;./?/init.lua;" .. package.path
 if not _G.love then _G.love = require("tests.love_stub") end
 
@@ -9,11 +9,12 @@ local GamepadMap = require("src.core.GamepadMap")
 
 GamepadMap._setForceNXForTests(true)
 
--- Phase 0 / naming diagnosis: Y→#3→a, X→#4→b; Nintendo B/A at #1/#2.
-eq(GamepadMap.mapRawButton(3), "a", "NX raw Y (#3) maps to GB A")
-eq(GamepadMap.mapRawButton(4), "b", "NX raw X (#4) maps to GB B")
-eq(GamepadMap.mapRawToGamepadButton(3), "a", "NX raw #3 routes to gamepad a")
-eq(GamepadMap.mapRawToGamepadButton(4), "b", "NX raw #4 routes to gamepad b")
+eq(GamepadMap.mapGamepadButton("b"), "a", "NX physical A (SDL b) -> GB A")
+eq(GamepadMap.mapGamepadButton("a"), "b", "NX physical B (SDL a) -> GB B")
+eq(GamepadMap.mapRawButton(1), "b", "NX raw #1 Nintendo B -> GB B")
+eq(GamepadMap.mapRawButton(2), "a", "NX raw #2 Nintendo A -> GB A")
+eq(GamepadMap.mapRawToGamepadButton(1), "a", "NX raw #1 routes as SDL south name")
+eq(GamepadMap.mapRawToGamepadButton(2), "b", "NX raw #2 routes as SDL east name")
 eq(GamepadMap.mapRawButton(9), "select", "NX minus (#9) -> select")
 eq(GamepadMap.mapRawButton(10), "start", "NX plus (#10) -> start")