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// SPDX-FIleCopyrightText: 2017 Francisco Lopes da Silva
// SPDX-FIleCopyrightText: 2023 Sam Nystrom <sam@samnystrom.dev>
// SPDX-License-Identifier: MIT
// Map the caps lock key to escape and caps+hjkl to the arrow keys
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdbool.h>
#include <linux/input.h>
const struct input_event
syn = {.type = EV_SYN, .code = SYN_REPORT, .value = 0},
esc_up = {.type = EV_KEY, .code = KEY_ESC , .value = 0},
esc_down = {.type = EV_KEY, .code = KEY_ESC , .value = 1};
const int delay = 10000;
void hjkl_to_arrow(struct input_event *event) {
switch (event->code) {
case KEY_H:
event->code = KEY_LEFT;
break;
case KEY_J:
event->code = KEY_DOWN;
break;
case KEY_K:
event->code = KEY_UP;
break;
case KEY_L:
event->code = KEY_RIGHT;
break;
}
}
int main(int argc, char** argv) {
setbuf(stdin, NULL);
setbuf(stdout, NULL);
enum { START, CAPSLOCK_HELD, CAPSLOCK_IS_MODIFIER } state = START;
// Handle cases where caps lock is released before hjkl is released so
// the subsequent hjkl release is properly rewritten as an arrow key
int down_key = KEY_RESERVED;
struct input_event event;
while (fread(&event, sizeof(event), 1, stdin) == 1) {
if (event.type == EV_MSC && event.code == MSC_SCAN) {
continue;
}
if (event.type != EV_KEY && event.type != EV_REL && event.type != EV_ABS) {
fwrite(&event, sizeof(event), 1, stdout);
continue;
}
switch (state) {
case START:
if (event.type == EV_KEY && event.code == KEY_CAPSLOCK && event.value) {
state = CAPSLOCK_HELD;
} else {
if (event.type == EV_KEY && event.code == down_key && event.value == 0) {
hjkl_to_arrow(&event);
down_key = KEY_RESERVED;
}
fwrite(&event, sizeof(event), 1, stdout);
}
break;
case CAPSLOCK_HELD:
if (event.type == EV_KEY && event.code == KEY_CAPSLOCK) {
if (event.value == 0) {
fwrite(&esc_down, sizeof(esc_down), 1, stdout);
fwrite(&syn, sizeof(syn), 1, stdout);
usleep(delay);
fwrite(&esc_up, sizeof(esc_up), 1, stdout);
state = START;
}
} else {
if (event.type == EV_KEY && event.value) {
down_key = event.code;
hjkl_to_arrow(&event);
state = CAPSLOCK_IS_MODIFIER;
}
if (event.type == EV_KEY && event.code == down_key && event.value == 0) {
down_key = KEY_RESERVED;
hjkl_to_arrow(&event);
}
fwrite(&event, sizeof(event), 1, stdout);
}
break;
case CAPSLOCK_IS_MODIFIER:
if (event.type == EV_KEY && event.code == KEY_CAPSLOCK) {
if (event.value == 0) {
state = START;
}
} else {
if (event.type == EV_KEY && event.value) {
down_key = event.code;
hjkl_to_arrow(&event);
}
if (event.type == EV_KEY && event.code == down_key && event.value == 0) {
down_key = KEY_RESERVED;
hjkl_to_arrow(&event);
}
fwrite(&event, sizeof(event), 1, stdout);
}
break;
}
}
}
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