// Copyright 2021-2022 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//
// For full documentation, see
// https://getreuer.info/posts/keyboards/autocorrection
#include "autocorrection.h"
#include <string.h>
#include "autocorrection_data.h"
#if AUTOCORRECTION_MIN_LENGTH < 4
// Odd output or hard locks on the board have been observed when the min typo
// length is 3 or lower (https://github.com/getreuer/qmk-keymap/issues/2).
// Additionally, autocorrection entries for short typos are more likely to false
// trigger, so it is suggested that typos be at least 5 characters.
#error "Min typo length is less than 4. Autocorrection may behave poorly."
#endif
bool process_autocorrection(uint16_t keycode, keyrecord_t* record) {
if (user_config.autocorrect) {
static uint8_t typo_buffer[AUTOCORRECTION_MAX_LENGTH] = {0};
static uint8_t typo_buffer_size = 0;
// Ignore key release; we only process key presses.
if (!record->event.pressed) { return true; }
#ifndef NO_ACTION_ONESHOT
const uint8_t mods = get_mods() | get_oneshot_mods();
#else
const uint8_t mods = get_mods();
#endif // NO_ACTION_ONESHOT
// Disable autocorrection while a mod other than shift is active.
if ((mods & ~MOD_MASK_SHIFT) != 0) {
typo_buffer_size = 0;
return true;
}
// The following switch cases address various kinds of keycodes. This logic is
// split over two switches rather than merged into one. The first switch may
// extract a basic keycode which is then further handled by the second switch,
// e.g. a layer-tap key with Caps Lock `LT(layer, KC_CAPS)`.
switch (keycode) {
#ifndef NO_ACTION_TAPPING
case QK_MOD_TAP ... QK_MOD_TAP_MAX: // Tap-hold keys.
#ifndef NO_ACTION_LAYER
case QK_LAYER_TAP ... QK_LAYER_TAP_MAX:
#endif // NO_ACTION_LAYER
// Ignore when tap-hold keys are held.
if (record->tap.count == 0) { return true; }
// Otherwise when tapped, get the basic keycode.
// Fallthrough intended.
#endif // NO_ACTION_TAPPING
// Handle shifted keys, e.g. symbols like KC_EXLM = S(KC_1).
case QK_LSFT ... QK_LSFT + 255:
case QK_RSFT ... QK_RSFT + 255:
keycode &= 0xff; // Get the basic keycode.
break;
// NOTE: Space Cadet keys expose no info to check whether they are being
// tapped vs. held. This makes autocorrection ambiguous, e.g. SC_LCPO might
// be '(', which we would treat as a word break, or it might be shift, which
// we would treat as having no effect. To behave cautiously, we allow Space
// Cadet keycodes to fall to the logic below and clear autocorrection state.
}
switch (keycode) {
// Ignore shifts, Caps Lock, one-shot mods, and layer switch keys.
case KC_NO:
case KC_LSFT:
case KC_RSFT:
case KC_CAPS:
case QK_ONE_SHOT_MOD ... QK_ONE_SHOT_MOD_MAX:
case QK_TO ... QK_TO_MAX:
case QK_MOMENTARY ... QK_MOMENTARY_MAX:
case QK_DEF_LAYER ... QK_DEF_LAYER_MAX:
case QK_TOGGLE_LAYER ... QK_TOGGLE_LAYER_MAX:
case QK_ONE_SHOT_LAYER ... QK_ONE_SHOT_LAYER_MAX:
case QK_LAYER_TAP_TOGGLE ... QK_LAYER_TAP_TOGGLE_MAX:
case QK_LAYER_MOD ... QK_LAYER_MOD_MAX:
return true; // Ignore these keys.
}
if (keycode == KC_QUOT) {
// Treat " (shifted ') as a word boundary.
if ((mods & MOD_MASK_SHIFT) != 0) { keycode = KC_SPC; }
} else if (!(KC_A <= keycode && keycode <= KC_Z)) {
if (keycode == KC_BSPC) {
// Remove last character from the buffer.
if (typo_buffer_size > 0) { --typo_buffer_size; }
return true;
} else if (KC_1 <= keycode && keycode <= KC_SLSH && keycode != KC_ESC) {
// Set a word boundary if space, period, digit, etc. is pressed.
// Behave more conservatively for the enter key. Reset, so that enter
// can't be used on a word ending.
if (keycode == KC_ENT) { typo_buffer_size = 0; }
keycode = KC_SPC;
} else {
// Clear state if some other non-alpha key is pressed.
typo_buffer_size = 0;
return true;
}
}
// If the buffer is full, rotate it to discard the oldest character.
if (typo_buffer_size >= AUTOCORRECTION_MAX_LENGTH) {
memmove(typo_buffer, typo_buffer + 1, AUTOCORRECTION_MAX_LENGTH - 1);
typo_buffer_size = AUTOCORRECTION_MAX_LENGTH - 1;
}
// Append `keycode` to the buffer.
// NOTE: `keycode` must be a basic keycode (0-255) by this point.
typo_buffer[typo_buffer_size++] = (uint8_t) keycode;
// Early return if not many characters have been buffered so far.
if (typo_buffer_size < AUTOCORRECTION_MIN_LENGTH) { return true; }
// Check whether the buffer ends in a typo. This is done using a trie
// stored in `autocorrection_data`.
uint16_t state = 0;
uint8_t code = pgm_read_byte(autocorrection_data + state);
for (int i = typo_buffer_size - 1; i >= 0; --i) {
const uint8_t key_i = typo_buffer[i];
if (code & 64) { // Check for match in node with multiple children.
code &= 63;
for (; code != key_i;
code = pgm_read_byte(autocorrection_data + (state += 3))) {
if (!code) { return true; }
}
// Follow link to child node.
state = (uint16_t)(
(uint_fast16_t)pgm_read_byte(autocorrection_data + state + 1)
| (uint_fast16_t)pgm_read_byte(autocorrection_data + state + 2) << 8);
// Otherwise check for match in node with a single child.
} else if (code != key_i) {
return true;
} else if (!(code = pgm_read_byte(autocorrection_data + (++state)))) {
++state;
}
// Stop if `state` becomes an invalid index. This should not normally
// happen, it is a safeguard in case of a bug, data corruption, etc.
if (state >= sizeof(autocorrection_data)) {
return true;
}
// Read first byte of the next node.
code = pgm_read_byte(autocorrection_data + state);
if (code & 128) { // A typo was found! Apply autocorrection.
const int backspaces = code & 63;
for (int i = 0; i < backspaces; ++i) { tap_code(KC_BSPC); }
send_string_P((char const*)(autocorrection_data + state + 1));
if (keycode == KC_SPC) {
typo_buffer[0] = KC_SPC;
typo_buffer_size = 1;
return true;
} else {
typo_buffer_size = 0;
return false;
}
}
}
return true;
}
return true;
}