FROM: htts://github.com/KenDickey/FBDevVM file sqEVTest.c
------

/*==================*/
/* Modifier/Adjunct Keys */
/*==================*/
static int leftAdjuncts  = 0;	/* left-  ctl, alt, shift, meta */
static int rightAdjuncts = 0;	/* right- ctl, alt, shift, meta */

int modifierState() {
  return ( leftAdjuncts | rightAdjuncts );
}

void clearModifierState() { 
  leftAdjuncts  = 0;
  rightAdjuncts = 0;
}

void updateModifierState(struct input_event* evt)
{  /* harmless if not modifier key */
  if (evt->type == EV_KEY) {
    if (evt->value == 1) { /* button down */
      switch (evt->code) {
	case KEY_LEFTMETA:   leftAdjuncts  |= CommandKeyBit; break;
	case KEY_LEFTALT:    leftAdjuncts  |= OptionKeyBit;  break;
	case KEY_LEFTCTRL:   leftAdjuncts  |= CtrlKeyBit;    break;
	case KEY_LEFTSHIFT:  leftAdjuncts  |= ShiftKeyBit;   break;
	case KEY_RIGHTMETA:  rightAdjuncts |= CommandKeyBit; break;
	case KEY_RIGHTALT:   rightAdjuncts |= OptionKeyBit;  break;
	case KEY_RIGHTCTRL:  rightAdjuncts |= CtrlKeyBit;    break;
	case KEY_RIGHTSHIFT: rightAdjuncts |= ShiftKeyBit;   break;
	default: break;
	}
     } else if (evt->value == 0) { /* button up */
       switch (evt->code) {
	case KEY_LEFTMETA:   leftAdjuncts  &= ~CommandKeyBit; break;
	case KEY_LEFTALT:    leftAdjuncts  &= ~OptionKeyBit;  break;
	case KEY_LEFTCTRL:   leftAdjuncts  &= ~CtrlKeyBit;    break;
	case KEY_LEFTSHIFT:  leftAdjuncts  &= ~ShiftKeyBit;   break;
	case KEY_RIGHTMETA:  rightAdjuncts &= ~CommandKeyBit; break;
	case KEY_RIGHTALT:   rightAdjuncts &= ~OptionKeyBit;  break;
	case KEY_RIGHTCTRL:  rightAdjuncts &= ~CtrlKeyBit;    break;
	case KEY_RIGHTSHIFT: rightAdjuncts &= ~ShiftKeyBit;   break;
	default: break;
        }
     }
    /* ignore repeats (evt->value == 2) */
  } 
}

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