From 544ddde113657a932275399f577a422a809d2880 Mon Sep 17 00:00:00 2001
From: Pascal Getreuer <50221757+getreuer@users.noreply.github.com>
Date: Mon, 27 Jan 2025 03:32:23 -0800
Subject: [Core] Add Chordal Hold, an "opposite hands rule" tap-hold option
 similar to Achordion, Bilateral Combinations. (#24560)
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* Chordal Hold: restrict what chords settle as hold

* Chordal Hold: docs and further improvements

* Fix formatting.

* Doc rewording and minor edit.

* Support Chordal Hold of multiple tap-hold keys.

* Fix formatting.

* Simplification and additional test.

* Fix formatting.

* Tighten tests.

* Add test two_mod_taps_same_hand_hold_til_timeout.

* Revise handing of pairs of tap-hold keys.

* Generate a default chordal_hold_layout.

* Document chordal_hold_handedness().

* Add license notice to new and branched files in PR.

* Add `tapping.chordal_hold` property for info.json.

* Update docs/reference_info_json.md

* Revise "hand" jsonschema.

* Chordal Hold: Improved layout handedness heuristic.

This commit improves the heuristic used in generate-keyboard-c for
inferring key handedness from keyboard.json geometry data.

Heuristic summary:

1. If the layout is symmetric (e.g. most split keyboards), guess the
   handedness based on the sign of (x - layout_x_midpoint).

2. Otherwise, if the layout has a key of >=6u width, it is probably the
   spacebar. Form a dividing line through the spacebar, nearly vertical
   but with a slight angle to follow typical row stagger.

3. Otherwise, assume handedness based on the widest horizontal
   separation.

I have tested this strategy on a couple dozen keyboards and found it to
work reliably.

* Use Optional instead of `| None`.

* Refactor to avoid lambdas.

* Remove trailing comma in chordal_hold_layout.

* Minor docs edits.

* Revise to allow combining multiple same-hand mods.

This commit revises Chordal Hold as described in discussion in
https://github.com/qmk/qmk_firmware/pull/24560#discussion_r1894655238

1. In "RCTL_T(KC_A)↓, RSFT_T(KC_C)↓, RCTL_T(KC_A)↑" before the tapping
   term, RCTL_T(KC_A) is settled as tapped.
2. In "RCTL_T(KC_A)↓, RSFT_T(KC_C)↓, RSFT_T(KC_C)↑", both RCTL_T(KC_A)
   and RSFT_T(KC_C) are settled as tapped.
3. In "RCTL_T(KC_A)↓, RSFT_T(KC_C)↓, KC_U↓" (all keys on the same side),
   both RCTL_T(KC_A) and RSFT_T(KC_C) are settled as tapped.
4. In "RCTL_T(KC_A)↓, RSFT_T(KC_C)↓, LSFT_T(KC_T)↓", with the third key
   on the other side, we allow Permissive Hold or Hold On Other Keypress
   to decide how/when to settle the keys.
5. In "RCTL_T(KC_A)↓, RSFT_T(KC_C)↓" held until the tapping term, the
   keys are settled as held.

1–3 provide same-hand roll protection. 4–5 are for combining multiple
same-hand modifiers.

I've updated the unit tests and have been running it on my keyboard, for
a few hours so far, and all seems good. I really like this scheme. It
allows combining same-side mods, yet it also has roll protection on
streaks. For me, this feels like Achordion, but clearly better streak
handling and improved responsiveness.

* Fix formatting.

* Add a couple tests with LT keys.

* Remove stale use of CHORDAL_HOLD_LAYOUT.

* Fix misspelling lastest -> latest

* Handling tweak for LTs and tests.

* Fix formatting.

* More tests with LT keys.

* Fix formatting.
---
 lib/python/qmk/cli/generate/keyboard_c.py | 138 ++++++++++++++++++++++++++++--
 1 file changed, 133 insertions(+), 5 deletions(-)

(limited to 'lib/python/qmk/cli/generate')

diff --git a/lib/python/qmk/cli/generate/keyboard_c.py b/lib/python/qmk/cli/generate/keyboard_c.py
index 228b320942..1978de4a22 100755
--- a/lib/python/qmk/cli/generate/keyboard_c.py
+++ b/lib/python/qmk/cli/generate/keyboard_c.py
@@ -1,5 +1,9 @@
 """Used by the make system to generate keyboard.c from info.json.
 """
+import bisect
+import dataclasses
+from typing import Optional
+
 from milc import cli
 
 from qmk.info import info_json
@@ -87,6 +91,7 @@ def _gen_matrix_mask(info_data):
         lines.append(f'    0b{"".join(reversed(mask[i]))},')
     lines.append('};')
     lines.append('#endif')
+    lines.append('')
 
     return lines
 
@@ -122,6 +127,128 @@ def _gen_joystick_axes(info_data):
 
     lines.append('};')
     lines.append('#endif')
+    lines.append('')
+
+    return lines
+
+
+@dataclasses.dataclass
+class LayoutKey:
+    """Geometric info for one key in a layout."""
+    row: int
+    col: int
+    x: float
+    y: float
+    w: float = 1.0
+    h: float = 1.0
+    hand: Optional[str] = None
+
+    @staticmethod
+    def from_json(key_json):
+        row, col = key_json['matrix']
+        return LayoutKey(
+            row=row,
+            col=col,
+            x=key_json['x'],
+            y=key_json['y'],
+            w=key_json.get('w', 1.0),
+            h=key_json.get('h', 1.0),
+            hand=key_json.get('hand', None),
+        )
+
+    @property
+    def cx(self):
+        """Center x coordinate of the key."""
+        return self.x + self.w / 2.0
+
+    @property
+    def cy(self):
+        """Center y coordinate of the key."""
+        return self.y + self.h / 2.0
+
+
+class Layout:
+    """Geometric info of a layout."""
+    def __init__(self, layout_json):
+        self.keys = [LayoutKey.from_json(key_json) for key_json in layout_json['layout']]
+        self.x_min = min(key.cx for key in self.keys)
+        self.x_max = max(key.cx for key in self.keys)
+        self.x_mid = (self.x_min + self.x_max) / 2
+        # If there is one key with width >= 6u, it is probably the spacebar.
+        i = [i for i, key in enumerate(self.keys) if key.w >= 6.0]
+        self.spacebar = self.keys[i[0]] if len(i) == 1 else None
+
+    def is_symmetric(self, tol: float = 0.02):
+        """Whether the key positions are symmetric about x_mid."""
+        x = sorted([key.cx for key in self.keys])
+        for i in range(len(x)):
+            x_i_mirrored = 2.0 * self.x_mid - x[i]
+            # Find leftmost x element greater than or equal to (x_i_mirrored - tol).
+            j = bisect.bisect_left(x, x_i_mirrored - tol)
+            if j == len(x) or abs(x[j] - x_i_mirrored) > tol:
+                return False
+
+        return True
+
+    def widest_horizontal_gap(self):
+        """Finds the x midpoint of the widest horizontal gap between keys."""
+        x = sorted([key.cx for key in self.keys])
+        x_mid = self.x_mid
+        max_sep = 0
+        for i in range(len(x) - 1):
+            sep = x[i + 1] - x[i]
+            if sep > max_sep:
+                max_sep = sep
+                x_mid = (x[i + 1] + x[i]) / 2
+
+        return x_mid
+
+
+def _gen_chordal_hold_layout(info_data):
+    """Convert info.json content to chordal_hold_layout
+    """
+    # NOTE: If there are multiple layouts, only the first is read.
+    for layout_name, layout_json in info_data['layouts'].items():
+        layout = Layout(layout_json)
+        break
+
+    if layout.is_symmetric():
+        # If the layout is symmetric (e.g. most split keyboards), guess the
+        # handedness based on the sign of (x - layout.x_mid).
+        hand_signs = [key.x - layout.x_mid for key in layout.keys]
+    elif layout.spacebar is not None:
+        # If the layout has a spacebar, form a dividing line through the spacebar,
+        # nearly vertical but with a slight angle to follow typical row stagger.
+        x0 = layout.spacebar.cx - 0.05
+        y0 = layout.spacebar.cy - 1.0
+        hand_signs = [(key.x - x0) - (key.y - y0) / 3.0 for key in layout.keys]
+    else:
+        # Fallback: assume handedness based on the widest horizontal separation.
+        x_mid = layout.widest_horizontal_gap()
+        hand_signs = [key.x - x_mid for key in layout.keys]
+
+    for key, hand_sign in zip(layout.keys, hand_signs):
+        if key.hand is None:
+            if key == layout.spacebar or abs(hand_sign) <= 0.02:
+                key.hand = '*'
+            else:
+                key.hand = 'L' if hand_sign < 0.0 else 'R'
+
+    lines = []
+    lines.append('#ifdef CHORDAL_HOLD')
+    line = ('__attribute__((weak)) const char chordal_hold_layout[MATRIX_ROWS][MATRIX_COLS] PROGMEM = ' + layout_name + '(')
+
+    x_prev = None
+    for key in layout.keys:
+        if x_prev is None or key.x < x_prev:
+            lines.append(line)
+            line = '  '
+        line += f"'{key.hand}', "
+        x_prev = key.x
+
+    lines.append(line[:-2])
+    lines.append(');')
+    lines.append('#endif')
 
     return lines
 
@@ -136,11 +263,12 @@ def generate_keyboard_c(cli):
     kb_info_json = info_json(cli.args.keyboard)
 
     # Build the layouts.h file.
-    keyboard_h_lines = [GPL2_HEADER_C_LIKE, GENERATED_HEADER_C_LIKE, '#include QMK_KEYBOARD_H', '']
+    keyboard_c_lines = [GPL2_HEADER_C_LIKE, GENERATED_HEADER_C_LIKE, '#include QMK_KEYBOARD_H', '']
 
-    keyboard_h_lines.extend(_gen_led_configs(kb_info_json))
-    keyboard_h_lines.extend(_gen_matrix_mask(kb_info_json))
-    keyboard_h_lines.extend(_gen_joystick_axes(kb_info_json))
+    keyboard_c_lines.extend(_gen_led_configs(kb_info_json))
+    keyboard_c_lines.extend(_gen_matrix_mask(kb_info_json))
+    keyboard_c_lines.extend(_gen_joystick_axes(kb_info_json))
+    keyboard_c_lines.extend(_gen_chordal_hold_layout(kb_info_json))
 
     # Show the results
-    dump_lines(cli.args.output, keyboard_h_lines, cli.args.quiet)
+    dump_lines(cli.args.output, keyboard_c_lines, cli.args.quiet)
-- 
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