[Keymap] New kbd67/hotswap keymap for writing both code and math (#4933)

* Custom keymap.

* Fix magic layer, enable Unicode.

* Update README.

* Make Unicode config change keymap-local.

* Move magic to AltGr, simplifying layout.

* Changes per Drashna.

* Fix magic+esc = backtick!

* Change reset implementation per Drashna's suggestion.

* Add a few more symbols so long as the commit is open - √ℜℂℤ⊙ℚℕ and the like.

* Typo fix.

* Slight simplification, drop an extra variable.

keyboards/kbd67/hotswap/keymaps/zunger/config.h

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+/* Copyright 2018 MechMerlin
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+// Enable cmd-option-escape on mac.
+#define GRAVE_ESC_ALT_OVERRIDE
+
+// place overrides here

keyboards/kbd67/hotswap/keymaps/zunger/keymap.c

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+/* Copyright 2019 Yonatan Zunger
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include QMK_KEYBOARD_H
+
+enum custom_keycodes {
+  // Use this instead of RALT, so we can use it to switch layers but not trigger other alt-related
+  // behavior (like GRAVE_ESC_ALT_OVERRIDE).
+  MAGIC = SAFE_RANGE,
+};
+
+enum layers_keymap {
+  _QWERTY = 0,
+  _FUNCTION,
+
+  _MAGIC,
+  _SHIFTMAGIC,
+};
+
+// This is so that H(xxxx) has the same width as _______, which makes the grids more legible.
+#define H(x) UC(0x##x)
+
+
+const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
+/* Keymap (Base Layer) Default Layer
+   * ,----------------------------------------------------------------.
+   * |Esc | 1|  2|  3|  4|  5|  6|  7|  8|  9|  0|  -|  =|Del|Brk|Home|
+   * |----------------------------------------------------------------|
+   * |Tab  |  Q|  W|  E|  R|  T|  Y|  U|  I|  O|  P|  [|  ]|  \  |End |
+   * |----------------------------------------------------------------|
+   * |Ctrl   |  A|  S|  D|  F|  G|  H|  J|  K|  L|  ;|  '|Return |PgUp|
+   * |----------------------------------------------------------------|
+   * |Shift   |  Z|  X|  C|  V|  B|  N|  M|  ,|  .|  /|Shift | Up|PgDn|
+   * |----------------------------------------------------------------|
+   * |Ctrl|Alt |Win |        Space          |Alt| FN |||||Lef|Dow|Rig |
+   * `----------------------------------------------------------------'
+   */
+[_QWERTY] = LAYOUT(
+  KC_GESC, KC_1,    KC_2,   KC_3,   KC_4,   KC_5,   KC_6,   KC_7,   KC_8,    KC_9,    KC_0,    KC_MINS, KC_EQL,  KC_BSPC, KC_BRK,  KC_HOME, \
+  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_END,  \
+  KC_LCTL, 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_PGUP, \
+  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_PGDN, \
+  KC_LCTL, KC_LALT, KC_LGUI,                KC_SPC,                          MAGIC,   MO(_FUNCTION),             KC_LEFT, KC_DOWN, KC_RGHT),
+
+  /* Keymap Fn Layer. Blank keys are deliberately NO, not TRNS.
+   * ,----------------------------------------------------------------.
+   * |Rst |F1| F2| F3| F4| F5| F6| F7| F8| F9|F10|F11|F12|F13|PSc|PAUS|
+   * |----------------------------------------------------------------|
+   * |Debug|   |   |   |   |   |   |   |   |   |   |   |   |     |    |
+   * |----------------------------------------------------------------|
+   * |Ctrl   |   |Vo+|   |   |   |   |   |   |   |   |   |       |    |
+   * |----------------------------------------------------------------|
+   * |Shift   |REV|Vo-|FWD|   |   |   |   |   |   |   |   McL|MsU|McR |
+   * |----------------------------------------------------------------|
+   * |Ctrl|Alt |Win |                       |Alt|    |||||MsL|MsD|MsR |
+   * `----------------------------------------------------------------'
+   */
+[_FUNCTION] = LAYOUT(
+   RESET,   KC_F1,   KC_F2,       KC_F3,   KC_F4,  KC_F5,  KC_F6,  KC_F7,  KC_F8,  KC_F9,   KC_F10, KC_F11, KC_F12, KC_F13, KC_PSCR,  KC_MPLY, \
+   DEBUG,   KC_NO,   KC_NO,       KC_NO,   KC_NO,  KC_NO,  KC_NO,  KC_NO,  KC_NO,  KC_NO,   KC_NO,  KC_NO,  KC_NO,  KC_NO,            _______,   \
+   _______, KC_NO,   KC__VOLUP,   KC_NO,   KC_NO,  KC_NO,  KC_NO,  KC_NO,  KC_NO,  KC_NO,   KC_NO,  KC_NO,          KC_NO,            KC_NO,   \
+   _______, KC_MRWD, KC__VOLDOWN, KC_MFFD, KC_NO,  KC_NO,  KC_NO,  KC_NO,  KC_NO,  KC_NO,   KC_NO,                  KC_BTN1, KC_MS_U, KC_BTN2, \
+   _______, _______, _______,                      KC_NO,                          _______, _______,                KC_MS_L, KC_MS_D, KC_MS_R),
+
+  /* Mathematical lower layer. Blank keys are TRNS.
+   * Note that escape turns into grave here. This doesn't just generalize GRAVE_ESC; it means that
+   * magic+esc is a way to create backticks without a dedicated key.
+   * ,----------------------------------------------------------------.
+   * | `  | ¹| ² | ³ | ⁴ | ⁵ | ⁶ | ⁷ | ⁸ | ⁹ | ⁰ | ⁻ | ⁺ | ⊕ | ≠ | √  |
+   * |----------------------------------------------------------------|
+   * |     | ± | ω | ε | ρ | τ | θ | υ | ι | ο | π | ∃ | ∀ |  ℚ  | ℝ  |
+   * |----------------------------------------------------------------|
+   * |       | α | σ | δ | φ | γ | η | ∅ | κ | λ | ∨ | ∧ |       | ℕ  |
+   * |----------------------------------------------------------------|
+   * |        | ζ | ξ | χ | ψ | β | ν | μ | ≲ | ≳ | ∈ |      | ↑ | ↔  |
+   * |----------------------------------------------------------------|
+   * |    |    |    |                       |   |    ||||| ← | ↓ | →  |
+   * `----------------------------------------------------------------'
+  */
+[_MAGIC] = LAYOUT(
+ KC_GRV,  H(00b9), H(00b2), H(00b3), H(2074), H(2075), H(2076), H(2077), H(2078), H(2079), H(2070), H(207b), H(207a), H(2295), H(2260), H(221a), \
+ _______, H(00b1), H(03c9), H(03b5), H(03c1), H(03c4), H(03b8), H(03c5), H(03b9), H(03bf), H(03c0), H(2203), H(2200), H(211a),          H(211d), \
+ _______, H(03b1), H(03c3), H(03b4), H(03c6), H(03b3), H(03b7), H(2205), H(03ba), H(03bb), H(2228), H(2227),          _______,          H(2115), \
+ _______, H(03b6), H(03be), H(03c7), H(03c8), H(03b2), H(03bd), H(03bc), H(2272), H(2273), H(2208),                   _______, H(2191), H(2194), \
+ _______, _______, _______,                   _______,                            _______, _______,                   H(2190), H(2193), H(2192)),
+
+  /* Mathematical upper layer. Blank keys are TRNS.
+   * ,----------------------------------------------------------------.
+   * | `  | ₁| ₂ | ₃ | ₄ | ₅ | ₆ | ₇ | ₈ | ₉ | ₀ | ₋ | ₊ | ⊗ | ≈ | ∂  |
+   * |----------------------------------------------------------------|
+   * |     | ∓ | Ω | Ε | Ρ | Τ | Θ | Υ | Ι | Ο | Π | ∄ | ∞ |  ⊙  | ℂ  |
+   * |----------------------------------------------------------------|
+   * |       | Α | Σ | Δ | Φ | Γ | Η | ¬ | Κ | Λ | ∪ | ∩ |       | ℤ  |
+   * |----------------------------------------------------------------|
+   * |        | Ζ | Ξ | Χ | Ψ | Β | Ν | Μ | ⊆ | ⊇ | ∉ |      | ⇑ | ⇔  |
+   * |----------------------------------------------------------------|
+   * |    |    |    |                       |   |    ||||| ⇐ | ⇓ | ⇒  |
+   * `----------------------------------------------------------------'
+  */
+[_SHIFTMAGIC] = LAYOUT(
+ KC_GRV,  H(2081), H(2082), H(2083), H(2084), H(2085), H(2086), H(2087), H(2088), H(2089), H(2080), H(208b), H(208a), H(2297), H(2248), H(2202), \
+ _______, H(2213), H(03a9), H(0395), H(03a1), H(03a4), H(0398), H(03a5), H(0399), H(039f), H(03a0), H(2204), H(221e), H(2299),          H(2102), \
+ _______, H(0391), H(03a3), H(0394), H(03a6), H(0393), H(0397), H(00ac), H(039a), H(039b), H(222a), H(2229),          _______,          H(2124), \
+ _______, H(0396), H(039e), H(03a7), H(03a8), H(0392), H(039d), H(039c), H(2286), H(2287), H(2209),                   _______, H(21d1), H(21d4), \
+ _______, _______, _______,                   _______,                            _______, _______,                   H(21d0), H(21d3), H(21d2)),
+};
+
+// Layer bitfields.
+#define MAGIC_LAYER (1UL << _MAGIC)
+#define SHIFTMAGIC_LAYER (1UL << _SHIFTMAGIC)
+// The layers we don't touch.
+#define LAYER_MASK ~(MAGIC_LAYER|SHIFTMAGIC_LAYER)
+
+bool process_record_user(uint16_t keycode, keyrecord_t *record) {
+  // Activate the appropriate magic layer:
+  //   User is holding AltGr+Shift => _SHIFTMAGIC
+  //   User is holding AltGr       => _MAGIC
+  //   Not holding AltGr           => None
+  // We do this the efficient way, by grabbing the non-magic bits from the current layer bitmap,
+  // setting the appropriate magic or shiftmagic bit, and doing an absolute layer set. (Layer
+  // sets are nontrivial, so we don't want to do extras!)
+
+  // We track shift and AltGr state on our own, because this function is called before get_mods is
+  // updated!
+  static bool shifted = false;
+  static bool magic = false;
+
+  if (keycode == KC_LSHIFT || keycode == KC_RSHIFT) {
+    shifted = record->event.pressed;
+  } else if (keycode == MAGIC) {
+    magic = record->event.pressed;
+  } else if (keycode == RESET) {
+    // Safe reset: Only actually let this keycode through if shift is held as well. Since there's no
+    // right-shift in the function layer, this means that reset is Fn+LShift+Esc, something you're
+    // not likely to hit by accident. (Especially since AltGr+Esc is backtick!)
+    return (record->event.pressed && shifted);
+  }
+
+  // Update the layer.
+  uint32_t new_layer_state = layer_state & LAYER_MASK;
+  if (magic) {
+    new_layer_state |= (shifted ? SHIFTMAGIC_LAYER : MAGIC_LAYER);
+  }
+  if (layer_state != new_layer_state) {
+    layer_state_set(new_layer_state);
+  }
+
+  return true;
+}
+
+void eeconfig_init_user(void) {
+  set_unicode_input_mode(UC_OSX);
+}
+
+void matrix_init_user(void) {
+}
+
+void matrix_scan_user(void) {
+
+}
+
+void led_set_user(uint8_t usb_led) {
+
+}

keyboards/kbd67/hotswap/keymaps/zunger/readme.md

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+* Custom keymap for kbd67, for those who need to both code and type math.
+* Author: Yonatan Zunger (zunger@gmail.com)
+
+This keymap is presently rather Mac-centric, as it uses Mac media keys in its function layer and the
+OS X Unicode input mode for the "magic" layers.
+
+*Layer 0 (Base QWERTY):* The layout has a few minor quirks: grave escape, Home/End/PgUp/PgDn in the
+right-hand column (rather than the more common Home/PgUp/PgDn/End), and a pause key between
+backspace and home -- this being something I use for screen lock, a necessity when one works with
+and sits next to security engineers. (Using a heavier switch on the pause key greatly reduces the
+risk of accidental triggering) In OS X style, alt and win are swapped on the left-hand side.
+
+The right-hand alt and gui keys take on a different meaning: right-alt lives up to its old name of
+AltGr by invoking Greek (the "magic" layers, 2 and 3), and right-gui invokes the function layer.
+
+*Layer 1 (Functions):* This layer deliberately sets KC_NO for the keys it doesn't use. I realize
+this isn't common, but I like to keep my functions quite distinct from all other layers.
+
+RESET can be accessed at Fn+Left Shift+Escape.
+
+*Layers 2 and 3*: These are invoked by the "magic" key (AltGr) and by magic+shift. The
+letters mostly produce Greek; the numbers, superscripts (magic) and subscripts (magic+shift); and
+the various other keys, mathematical symbols. There unfortunately aren't nearly enough keys for all
+the symbols I'd like, so magic+alt and magic+alt+shift may end up existing as well, giving this a
+proper Space Cadet effect; but that said, it's going to be hard to remember where all these symbols
+are without some extremely custom keycaps. In the limit of arbitrarily complex layers, the keyboard
+will probably start running LISP and turn into EMACS.

keyboards/kbd67/hotswap/keymaps/zunger/rules.mk

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+# You need Unicode for this map.
+UNICODE_ENABLE = yes        # Unicode