Basic mac vs linux modes

.gitignore

@@ -1,3 +1,2 @@
 result
 .build/
-qmk_firmware/

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "qmk_firmware"]
+	path = qmk_firmware
+	url = https://github.com/system76/qmk_firmware.git

flake.nix

@@ -3,6 +3,7 @@
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    self.submodules = true;
   };
 
   outputs = { self, nixpkgs }:
@@ -23,11 +24,7 @@
 
             shellHook = ''
               export QMK_HOME="$PWD/qmk_firmware"
-
+              ln -sfn "$PWD/keymaps/custom" "$QMK_HOME/keyboards/system76/launch_3/keymaps/custom"
-              # Symlink tracked keymap into QMK tree
-              if [ -d "$QMK_HOME/keyboards/system76/launch_3" ]; then
-                ln -sfn "$PWD/keymaps/custom" "$QMK_HOME/keyboards/system76/launch_3/keymaps/custom"
-              fi
             '';
           };
         });
@@ -35,20 +32,32 @@
       packages = forAllSystems (system:
         let pkgs = nixpkgs.legacyPackages.${system};
         in {
+          default = self.packages.${system}.firmware;
+
           firmware = pkgs.stdenv.mkDerivation {
             pname = "launch3-firmware";
             version = "0.1.0";
 
             src = ./qmk_firmware;
 
+            postUnpack = ''
+              cp -r ${./keymaps/custom} $sourceRoot/keyboards/system76/launch_3/keymaps/custom
+            '';
+
+            postPatch = ''
+              patchShebangs util/uf2conv.py
+            '';
+
             nativeBuildInputs = [
               pkgs.qmk
               pkgs.python3Packages.appdirs
+              pkgs.python3
             ];
 
             buildPhase = ''
               export HOME=$(mktemp -d)
               export QMK_HOME="$PWD"
+              export SKIP_GIT=true
               qmk compile -kb system76/launch_3 -km custom
             '';
 

keymaps/custom/keymap.c

@@ -1,4 +1,66 @@
 #include QMK_KEYBOARD_H
+#include "keymap_introspection.h"
+#include "dynamic_keymap.h"
+#include "mac_mode.h"
+
+enum custom_keycodes {
+    CK_MCMD = SAFE_RANGE, // toggle mac-command mode
+};
+
+typedef struct {
+    uint8_t from;
+    uint8_t to;
+} mod_rewrite_t;
+
+static const mod_rewrite_t CTRL_TO_SUPER           = { MOD_MASK_CTRL,                   MOD_MASK_GUI };
+static const mod_rewrite_t CTRL_SHIFT_TO_SUPER     = { MOD_MASK_CTRL | MOD_MASK_SHIFT,  MOD_MASK_GUI };
+static const mod_rewrite_t CTRL_SHIFT_TO_CMD_SHIFT = { MOD_MASK_CTRL | MOD_MASK_SHIFT,  MOD_MASK_GUI | MOD_MASK_SHIFT };
+static const mod_rewrite_t CTRL_ALT_TO_CTRL        = { MOD_MASK_CTRL | MOD_MASK_ALT,    MOD_MASK_CTRL };
+static const mod_rewrite_t CTRL_TO_ALT             = { MOD_MASK_CTRL,                   MOD_MASK_ALT };
+static const mod_rewrite_t ALT_TO_SUPER            = { MOD_MASK_ALT,                    MOD_MASK_GUI };
+static const mod_rewrite_t SUPER_TO_SUPER          = { MOD_MASK_GUI,                    MOD_MASK_GUI };
+static const mod_rewrite_t SUPER_TO_CTRL           = { MOD_MASK_GUI,                    MOD_MASK_CTRL };
+static const mod_rewrite_t NONE_TO_SUPER           = { 0,                               MOD_MASK_GUI };
+
+// Collapse left/right mods into modifier types for comparison.
+// e.g. either LCTL (0x01) or RCTL (0x10) both become 0x01.
+static uint8_t normalize_mods(uint8_t mods) {
+    return (mods | (mods >> 4)) & 0x0F;
+}
+
+// Check if current mods exactly match a rule's `from` mods.
+// Returns false if FN layer is active (skip rewrites when FN is held).
+static bool mods_match(uint8_t mods, mod_rewrite_t rule) {
+    if (layer_state_is(1)) return false;
+    return normalize_mods(mods) == normalize_mods(rule.from);
+}
+
+// Rewrite modifier combos: swap exact `from` mod types to `to` mods, tap keycode, restore.
+// Left/right variants of the same modifier are treated as equivalent.
+// Returns true if rewrite occurred.
+static bool rewrite_mods(uint16_t keycode, mod_rewrite_t rule) {
+    uint8_t mods = get_mods();
+    if (mods_match(mods, rule)) {
+        set_mods(normalize_mods(rule.to));
+        tap_code(keycode);
+        set_mods(mods);
+        return true;
+    }
+    return false;
+}
+
+// Rewrite modifier combo AND change the keycode sent.
+// Returns true if rewrite occurred.
+static bool rewrite_mods_and_key(mod_rewrite_t rule, uint16_t keycode_out) {
+    uint8_t mods = get_mods();
+    if (mods_match(mods, rule)) {
+        set_mods(normalize_mods(rule.to));
+        tap_code(keycode_out);
+        set_mods(mods);
+        return true;
+    }
+    return false;
+}
 
 const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
 
@@ -20,7 +82,7 @@ ________________________________________________________________________________
   |     SHIFT      |   Z    |   X    |   C    |   V    |   B    |   N    |   M    |   <    |    >   |   ?    |   SHIFT    |   UP   |
   |________________|________|________|________|________|________|________|________|________|________|________|____________|________|_________
   |            |        |       |        |                 |                 |        |        |             |   |        |        |        |
-  |    CTRL    |  LALT  | FN    | LGUI   |    SPACE        |      SPACE      | RCTRL  |  RALT  |     FN      |   |  LEFT  |  DOWN  | RIGHT  |
+  |    CTRL    |  FN    | LGUI  | LALT   |    SPACE        |      SPACE      | RALT   |  RCTRL |     FN      |   |  LEFT  |  DOWN  | RIGHT  |
   |____________|________|_______|________|_________________|_________________|________|________|_____________|   |________|________|________|
 */
 
@@ -30,13 +92,13 @@ ________________________________________________________________________________
         KC_TAB,  KC_Q,    KC_W,    KC_E,    KC_R,    KC_T,    KC_Y,    KC_U,    KC_I,    KC_O,    KC_P,    KC_LBRC, KC_RBRC, KC_BSLS,  KC_PGDN,
           KC_CAPS, KC_A,    KC_S,    KC_D,    KC_F,    KC_G,    KC_H,    KC_J,    KC_K,    KC_L,    KC_SCLN, KC_QUOT,    KC_ENT,       KC_END,
           KC_LSFT,     KC_Z,    KC_X,    KC_C,    KC_V,    KC_B,    KC_N,    KC_M,    KC_COMM, KC_DOT,  KC_SLSH,    KC_RSFT,    KC_UP,
-          KC_LCTL, KC_LALT, MO(1),   KC_LGUI,     KC_SPC,           KC_SPC,     KC_RCTL,   KC_RALT,   MO(1),         KC_LEFT, KC_DOWN, KC_RGHT
+          KC_LCTL, MO(1),   KC_LGUI, KC_LALT,     KC_SPC,           KC_SPC,     KC_RALT,   KC_RCTL,   MO(1),         KC_LEFT, KC_DOWN, KC_RGHT
   ),
 
     /* Layer 1, function layer
 __________________________________________________________________________________________________________________________________  ________
 |        |        |        |        |        |        |        |        |        |        |        |        |        |            || PLAY/  |
-| QK_BOOT  |        |        |        |        |        |        |        |        |        |        |        |        |            || PAUSE  |
+|QK_BOOT |        |        |        |        |        |        |        |        |        |        |        |        |            || PAUSE  |
 |________|________|________|________|________|________|________|________|________|________|________|________|________|____________||________|
 |        |        |        |        |        |        |        |        |        |        |  LED   |  LED   |  LED   |            || VOLUME |
 |        |        |        |        |        |        |        |        |        |        | TOGGLE |  DOWN  |  UP    |            ||   UP   |
@@ -59,7 +121,7 @@ ________________________________________________________________________________
 */
 
   [1] = LAYOUT(
-    QK_BOOT,   KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS,     KC_MPLY,
+    QK_BOOT,   KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, CK_MCMD,     KC_MPLY,
     KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, RGB_TOG, RGB_VAD, RGB_VAI, KC_TRNS,     KC_VOLU,
         KC_PSCR, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_HOME, KC_PGDN, KC_PGUP, KC_END,  KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_VOLD,
           KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS, KC_LEFT, KC_DOWN, KC_UP,   KC_RGHT, KC_TRNS, KC_TRNS,    KC_TRNS,     KC_MUTE,
@@ -86,6 +148,153 @@ ________________________________________________________________________________
   ),
 };
 
+// Override layer resolution: in mac mode, any modifier forces layer 0 (ignores FN)
+uint16_t keymap_key_to_keycode(uint8_t layer, keypos_t key) {
+    if (mac_mode && (get_mods() & (MOD_MASK_CTRL | MOD_MASK_SHIFT | MOD_MASK_ALT | MOD_MASK_GUI))) {
+        layer = 0;
+    }
+    if (key.row < MATRIX_ROWS && key.col < MATRIX_COLS) {
+        return keycode_at_keymap_location(layer, key.row, key.col);
+    }
+    return KC_NO;
+}
+
+static bool gui_tapped = false;
+
 bool process_record_user(uint16_t keycode, keyrecord_t *record) {
+    // Any other key pressed while GUI held means it's being used as a modifier
+    if (record->event.pressed && keycode != KC_LGUI) {
+        gui_tapped = false;
+    }
+
+    switch (keycode) {
+        // Mac mode: tap Super -> Cmd+Space (Spotlight)
+        // Linux: tap Super passes through normally (KDE app menu)
+        case KC_LGUI:
+            if (mac_mode) {
+                if (record->event.pressed) {
+                    gui_tapped = true;
+                    register_mods(MOD_BIT(KC_LGUI));
+                } else {
+                    if (gui_tapped) {
+                        tap_code(KC_SPC); // GUI still held, sends Super+Space
+                        gui_tapped = false;
+                    }
+                    unregister_mods(MOD_BIT(KC_LGUI));
+                }
+                return false;
+            }
+            break;
+        case CK_MCMD:
+            if (record->event.pressed) {
+                mac_mode = !mac_mode;
+                mac_mode_manual = true;
+                // Flash LEDs to indicate mode: green = mac, red = normal
+                rgb_matrix_mode_noeeprom(RGB_MATRIX_SOLID_COLOR);
+                if (mac_mode) {
+                    rgb_matrix_sethsv_noeeprom(HSV_GREEN);
+                } else {
+                    rgb_matrix_sethsv_noeeprom(HSV_BLUE);
+                }
+            }
+            return false;
+        // Mac mode rewrites:
+        //   Ctrl+C/V       -> Super+C/V   (copy/paste)
+        //   Ctrl+Shift+C/V -> Super+C/V   (terminal copy/paste)
+        case KC_C:
+        case KC_V:
+            if (mac_mode && record->event.pressed) {
+                if (rewrite_mods(keycode, CTRL_TO_SUPER)) return false;
+                if (rewrite_mods(keycode, CTRL_SHIFT_TO_SUPER)) return false;
+            }
+            break;
+        // Mac mode rewrites:
+        //   Ctrl+X/A/S/F   -> Super+X/A/S/F      (cut, select all, save, find)
+        //   Ctrl+W/L/R     -> Super+W/L/R         (close tab, address bar, reload)
+        case KC_X:
+        case KC_A:
+        case KC_S:
+        case KC_F:
+        case KC_W:
+        case KC_L:
+        case KC_R:
+            if (mac_mode && record->event.pressed) {
+                if (rewrite_mods(keycode, CTRL_TO_SUPER)) return false;
+            }
+            break;
+        // Mac mode rewrites:
+        //   Ctrl+Z/T/N       -> Super+Z/T/N        (undo, new tab, new window)
+        //   Ctrl+Shift+Z/T/N -> Super+Shift+Z/T/N  (redo, reopen tab, incognito)
+        case KC_Z:
+        case KC_T:
+        case KC_N:
+            if (mac_mode && record->event.pressed) {
+                if (rewrite_mods(keycode, CTRL_TO_SUPER)) return false;
+                if (rewrite_mods(keycode, CTRL_SHIFT_TO_CMD_SHIFT)) return false;
+            }
+            break;
+        // Mac mode rewrites:
+        //   Ctrl+Alt+Left/Right -> Ctrl+Left/Right   (switch workspace)
+        //   Ctrl+Left/Right -> Alt+Left/Right         (word navigation)
+        case KC_LEFT:
+        case KC_RGHT:
+            if (mac_mode && record->event.pressed) {
+                if (rewrite_mods(keycode, CTRL_ALT_TO_CTRL)) return false;
+                if (rewrite_mods(keycode, CTRL_TO_ALT)) return false;
+            }
+            break;
+        // Mac mode rewrites:
+        //   Ctrl+Backspace -> Alt+Backspace   (delete word backward)
+        case KC_BSPC:
+            if (mac_mode && record->event.pressed) {
+                if (rewrite_mods(keycode, CTRL_TO_ALT)) return false;
+            }
+            break;
+        // Mac mode rewrites:
+        //   Home -> Super+Left    (line start)
+        //   End  -> Super+Right   (line end)
+        case KC_HOME:
+            if (mac_mode && record->event.pressed) {
+                if (rewrite_mods_and_key(NONE_TO_SUPER, KC_LEFT)) return false;
+            }
+            break;
+        case KC_END:
+            if (mac_mode && record->event.pressed) {
+                if (rewrite_mods_and_key(NONE_TO_SUPER, KC_RGHT)) return false;
+            }
+            break;
+        // Mac mode rewrites:
+        //   Alt+F4  -> Super+Q   (quit app)
+        case KC_F4:
+            if (mac_mode && record->event.pressed) {
+                if (rewrite_mods_and_key(ALT_TO_SUPER, KC_Q)) return false;
+            }
+            break;
+        // Mac mode rewrites:
+        //   Alt+Tab -> Super+Tab   (app switcher)
+        case KC_TAB:
+            if (mac_mode && record->event.pressed) {
+                if (rewrite_mods(keycode, ALT_TO_SUPER)) return false;
+            }
+            break;
+        // Workspace overview (both modes):
+        //   Super+Up -> Super+W   (KDE overview, linux)
+        //   Super+Up -> Ctrl+Up   (Mission Control, mac)
+        case KC_UP:
+            if (record->event.pressed) {
+                if (mac_mode) {
+                    if (rewrite_mods(keycode, SUPER_TO_CTRL)) return false;
+                } else {
+                    if (rewrite_mods_and_key(SUPER_TO_SUPER, KC_W)) return false;
+                }
+            }
+            break;
+    }
     return true;
 }
+
+void matrix_init_user(void) {
+    // Force dynamic keymap reset so PROGMEM keymaps always take effect
+    dynamic_keymap_reset();
+}
+

keymaps/custom/mac_mode.h

@@ -0,0 +1,6 @@
+#pragma once
+
+#include <stdbool.h>
+
+extern bool mac_mode;
+extern bool mac_mode_manual;

keymaps/custom/os_detect.c

@@ -0,0 +1,31 @@
+#include "os_detection.h"
+#include "timer.h"
+#include "rgb_matrix.h"
+
+#include "mac_mode.h"
+
+bool mac_mode = false;
+bool mac_mode_manual = false;
+static bool os_detected = false;
+static uint32_t flash_start = 0;
+
+// Poll OS detection after USB enumeration settles (~2s)
+// Flash indicator color for 500ms then restore default animation
+void matrix_scan_user(void) {
+    if (!os_detected && !mac_mode_manual && timer_elapsed32(0) > 2000) {
+        os_detected = true;
+        os_variant_t os = detected_host_os();
+        mac_mode = (os == OS_MACOS || os == OS_IOS);
+        rgb_matrix_mode_noeeprom(RGB_MATRIX_SOLID_COLOR);
+        if (mac_mode) {
+            rgb_matrix_sethsv_noeeprom(HSV_GREEN);
+        } else {
+            rgb_matrix_sethsv_noeeprom(HSV_BLUE);
+        }
+        flash_start = timer_read32();
+    }
+    if (flash_start && timer_elapsed32(flash_start) > 500) {
+        flash_start = 0;
+        rgb_matrix_reload_from_eeprom();
+    }
+}

keymaps/custom/rules.mk

@@ -0,0 +1,2 @@
+OS_DETECTION_ENABLE = yes
+SRC += os_detect.c

shell.nix

@@ -0,0 +1 @@
+(builtins.getFlake (toString ./.)).devShells.${builtins.currentSystem}.default