MOD TAP filtering without modifing QMK firmware

modtap-filter.c

#define ssend_string(...) {char ssendbuf[32];sprintf(ssendbuf,__VA_ARGS__);send_string(ssendbuf);}

static int8_t cntPressing = 0;
static uint16_t timeReleased = 0;
static bool fTappable = false;
static bool fTapping = false;

static uint16_t valTimeMODTAP = 300;
static uint16_t selParam = (uint16_t)SEL_MODTAP;

bool process_modtap_filter(uint16_t keycode, keyrecord_t *record) {

    if (!record->event.pressed) {
        cntPressing--;
        if(cntPressing == 0) {
            timeReleased = timer_read(); 
        } 
    }
    else {
        cntPressing++;
        if(cntPressing == 1) {
            uint16_t elapsed = TIMER_DIFF_16(record->event.time,timeReleased );
            fTappable = ( valTimeMODTAP < elapsed );  
        }

        switch(keycode) {
            case VAL_UP:
            case VAL_DN:
            {
                bool fup = (keycode == VAL_UP);
                switch(selParam) {
                    case SEL_MODTAP:
                    {
                        if(fup)
                            valTimeMODTAP += 10;
                        else
                            valTimeMODTAP -= 10;
                        
                        if(valTimeMODTAP<30)
                            valTimeMODTAP = 30;
                        if(valTimeMODTAP>500)
                            valTimeMODTAP = 500;
                    }
                    break;
                }
            }
            break;

            case SEL_VOL:    selParam = (uint16_t)SEL_VOL;    break;
            case SEL_MODTAP: selParam = (uint16_t)SEL_MODTAP; break;
            case REPORT:
                ssend_string("modtap:%u",valTimeMODTAP);
                break;
        }
    }

    //
    uint8_t modkey = 0;
    bool fTapcode = QK_MOD_TAP <= keycode && keycode <= QK_MOD_TAP_MAX; 
    if(fTapcode) {
        modkey = (keycode >> 8) & 0x1f;
        if( modkey == MOD_LSFT || modkey == MOD_RSFT )
            fTapcode = false;
    }
    if(cntPressing == 1 && record->event.pressed ) {
        if(fTapcode) {
            if( fTappable ) {
                fTapping = true;
                return true;
            } 
            else {
                fTappable = false; 
                fTapping = false;
                register_code(keycode & 0xff);
                unregister_code(keycode & 0xff);
                return false;
            }
        }
        else {
            fTappable = false; 
            fTapping = false;
        }
    }
    else if (!fTapping){
        if( fTapcode ) {
            if(record->event.pressed) {
                register_code(keycode & 0xff);
                unregister_code(keycode & 0xff);
                return false;
            }
            else {
                return false;
            }
        }
    }

    return true;
}

#define MODTAP_FILTER_PROC \
    if( ! process_modtap_filter(keycode,record) ) return false;

keymap.c　で、
#include に、次のように追加する。
#include "modtap-filter.c"

次のようなカスタムキーコードの定義を追加する。

enum custom_keycodes {
  BASE = SAFE_RANGE,
  REPORT,
  SEL_VOL,
  SEL_MODTAP,
  VAL_UP,
  VAL_DN,
};

process_record_userの先頭に、次のように追加する。

bool process_record_user(uint16_t keycode, keyrecord_t *record) {
    MODTAP_FILTER_PROC;