Caps Word and Layer Lock for vial-qmk.

* Enable Caps Word and Layer Lock. Set CAPS_WORD_INVERT_ON_SHIFT.
* Use the last bits of dynamic_vial_get_number_of_entries to indicate
  optionally supported features.
* Vial protocol version was already bumped to 6, matching the bump on
  made on the GUI side corresponding to this change.

builddefs/build_vial.mk

@@ -6,8 +6,10 @@ TAP_DANCE_ENABLE ?= yes
 ifeq ($(strip $(TAP_DANCE_ENABLE)), yes)
     OPT_DEFS += -DTAPPING_TERM_PER_KEY
 endif
+CAPS_WORD_ENABLE ?= yes
 COMBO_ENABLE ?= yes
 KEY_OVERRIDE_ENABLE ?= yes
+LAYER_LOCK_ENABLE ?= yes
 SRC += $(QUANTUM_DIR)/vial.c
 OPT_DEFS += -DVIAL_ENABLE -DNO_DEBUG -DSERIAL_NUMBER=\"vial:f64c2b3c\"
 
@@ -26,7 +28,7 @@ ifeq ($(strip $(QMK_SETTINGS)), yes)
     OPT_DEFS += -DQMK_SETTINGS \
         -DAUTO_SHIFT_NO_SETUP -DAUTO_SHIFT_REPEAT_PER_KEY -DAUTO_SHIFT_NO_AUTO_REPEAT_PER_KEY \
         -DPERMISSIVE_HOLD_PER_KEY -DHOLD_ON_OTHER_KEY_PRESS_PER_KEY -DQUICK_TAP_TERM_PER_KEY -DRETRO_TAPPING_PER_KEY \
-        -DCOMBO_TERM_PER_COMBO -DCHORDAL_HOLD -DFLOW_TAP_TERM=321
+        -DCOMBO_TERM_PER_COMBO -DCHORDAL_HOLD -DFLOW_TAP_TERM=321 -DCAPS_WORD_INVERT_ON_SHIFT
 endif
 
 # Generate Vial layout definition header from JSON

quantum/vial.c

@@ -224,6 +224,16 @@ void vial_handle_cmd(uint8_t *msg, uint8_t length) {
                 msg[0] = VIAL_TAP_DANCE_ENTRIES;
                 msg[1] = VIAL_COMBO_ENTRIES;
                 msg[2] = VIAL_KEY_OVERRIDE_ENTRIES;
+
+                // The last byte of msg indicates optionally supported features.
+                msg[length - 1] = (0
+#ifdef CAPS_WORD_ENABLE
+                        | (1 << 0)  // Bit 0: Caps Word.
+#endif
+#ifdef LAYER_LOCK_ENABLE
+                        | (1 << 1)  // Bit 1: Layer Lock.
+#endif
+                        );
                 break;
             }
 #ifdef VIAL_TAP_DANCE_ENABLE