feat(nx-mods): map Select+face chords to display hotkeys

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

src/core/GamepadMap.lua

@@ -67,6 +67,24 @@ function GamepadMap.mapGamepadButton(button)
   return GamepadMap.gamepadBindings()[button]
 end
 
+-- Select+face display chords (docs / Nintendo UX):
+--   Select+A → "2" (COLORS), Select+B → "3" (TILT),
+--   Select+Y → "5", Select+X → "6", Select+L (leftshoulder) → "7".
+-- For a/b: resolve through mapGamepadButton then GB a→"2", b→"3" so NX
+-- Nintendo physical A/B match the docs despite SDL face-label swap.
+-- Caller (Game:gamepadpressed) must require Select held; this is map-only.
+function GamepadMap.displayChordDigit(gamepadButton)
+  if gamepadButton == "y" then return "5" end
+  if gamepadButton == "x" then return "6" end
+  if gamepadButton == "leftshoulder" then return "7" end
+  if gamepadButton == "a" or gamepadButton == "b" then
+    local gb = GamepadMap.mapGamepadButton(gamepadButton)
+    if gb == "a" then return "2" end
+    if gb == "b" then return "3" end
+  end
+  return nil
+end
+
 -- love-nx / SDL: when isGamepad(), face+menu already arrive via gamepad*.
 -- Applying joystickpressed raw on top double-fires GB A/B in one frame.
 function GamepadMap.ignoreRawForJoystick(joystick)

tests/engine/input_display_chord_test.lua

@@ -0,0 +1,43 @@
+-- Select+face display chord digit map (NXMOD-06..09).
+-- Spec: Nintendo UX A/B → keys 2/3; Y/X/L → 5/6/7. Map-only (Select held is Game's job).
+package.path = "./?.lua;./?/init.lua;" .. package.path
+if not _G.love then _G.love = require("tests.love_stub") end
+
+local T = require("tests.harness")
+local check = T.check
+local eq = T.eq
+
+local GamepadMap = require("src.core.GamepadMap")
+
+-- Desktop / default: SDL face labels map identity for A/B chords.
+GamepadMap._setForceNXForTests(false)
+eq(GamepadMap.displayChordDigit("a"), "2", "desktop SDL a (GB A) -> key 2")
+eq(GamepadMap.displayChordDigit("b"), "3", "desktop SDL b (GB B) -> key 3")
+eq(GamepadMap.displayChordDigit("y"), "5", "Y -> key 5")
+eq(GamepadMap.displayChordDigit("x"), "6", "X -> key 6")
+eq(GamepadMap.displayChordDigit("leftshoulder"), "7", "leftshoulder (L) -> key 7")
+
+-- Unmapped buttons yield nil (no accidental digit).
+eq(GamepadMap.displayChordDigit("start"), nil, "start is not a display chord")
+eq(GamepadMap.displayChordDigit("back"), nil, "back/Select alone is not a digit")
+eq(GamepadMap.displayChordDigit("dpup"), nil, "d-pad is not a display chord")
+eq(GamepadMap.displayChordDigit("rightshoulder"), nil, "R is not a display chord")
+eq(GamepadMap.displayChordDigit(nil), nil, "nil button -> nil")
+
+-- NX Nintendo UX: GamepadMap swaps SDL a/b so physical A/B match docs.
+-- Physical Nintendo A arrives as SDL "b" → GB a → key "2".
+-- Physical Nintendo B arrives as SDL "a" → GB b → key "3".
+GamepadMap._setForceNXForTests(true)
+eq(GamepadMap.mapGamepadButton("b"), "a", "precondition: NX SDL east -> GB A")
+eq(GamepadMap.mapGamepadButton("a"), "b", "precondition: NX SDL south -> GB B")
+eq(GamepadMap.displayChordDigit("b"), "2",
+  "NX physical A (SDL b / GB a) -> key 2")
+eq(GamepadMap.displayChordDigit("a"), "3",
+  "NX physical B (SDL a / GB b) -> key 3")
+-- Y/X/L unchanged under NX face swap.
+eq(GamepadMap.displayChordDigit("y"), "5", "NX Y -> key 5")
+eq(GamepadMap.displayChordDigit("x"), "6", "NX X -> key 6")
+eq(GamepadMap.displayChordDigit("leftshoulder"), "7", "NX L -> key 7")
+GamepadMap._setForceNXForTests(false)
+
+T.finish()