feat(underglow): Add RGB auto off timeout on idle and on usb disconnect

app/Kconfig

@@ -325,6 +325,13 @@ config ZMK_RGB_UNDERGLOW_ON_START
 	bool "RGB underglow starts on by default"
 	default y
 
+config ZMK_RGB_UNDERGLOW_AUTO_OFF_IDLE
+	bool "Turn off RGB underglow when keyboard goes into idle state"
+
+config ZMK_RGB_UNDERGLOW_AUTO_OFF_USB
+	bool "Turn off RGB underglow when USB is disconnected"
+	depends on USB_DEVICE_STACK
+
 #ZMK_RGB_UNDERGLOW
 endif
 

app/src/rgb_underglow.c

@@ -19,6 +19,12 @@
 
 #include <zmk/rgb_underglow.h>
 
+#include <zmk/activity.h>
+#include <zmk/usb.h>
+#include <zmk/event_manager.h>
+#include <zmk/events/activity_state_changed.h>
+#include <zmk/events/usb_conn_state_changed.h>
+
 LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
 
 #define STRIP_LABEL DT_LABEL(DT_CHOSEN(zmk_underglow))
@@ -265,7 +271,13 @@ static int zmk_rgb_underglow_init(const struct device *_arg) {
     settings_load_subtree("rgb/underglow");
 #endif
 
-    k_timer_start(&underglow_tick, K_NO_WAIT, K_MSEC(50));
+#if IS_ENABLED(CONFIG_ZMK_RGB_UNDERGLOW_AUTO_OFF_USB)
+    state.on = zmk_usb_is_powered();
+#endif
+
+    if (state.on) {
+        k_timer_start(&underglow_tick, K_NO_WAIT, K_MSEC(50));
+    }
 
     return 0;
 }
@@ -444,4 +456,53 @@ int zmk_rgb_underglow_change_spd(int direction) {
     return zmk_rgb_underglow_save_state();
 }
 
+#if IS_ENABLED(CONFIG_ZMK_RGB_UNDERGLOW_AUTO_OFF_IDLE) ||                                          \
+    IS_ENABLED(CONFIG_ZMK_RGB_UNDERGLOW_AUTO_OFF_USB)
+static int rgb_underglow_auto_state(bool *prev_state, bool new_state) {
+    if (state.on == new_state) {
+        return 0;
+    }
+    if (new_state) {
+        state.on = *prev_state;
+        *prev_state = false;
+        return zmk_rgb_underglow_on();
+    } else {
+        state.on = false;
+        *prev_state = true;
+        return zmk_rgb_underglow_off();
+    }
+}
+
+static int rgb_underglow_event_listener(const zmk_event_t *eh) {
+
+#if IS_ENABLED(CONFIG_ZMK_RGB_UNDERGLOW_AUTO_OFF_IDLE)
+    if (as_zmk_activity_state_changed(eh)) {
+        static bool prev_state = false;
+        return rgb_underglow_auto_state(&prev_state,
+                                        zmk_activity_get_state() == ZMK_ACTIVITY_ACTIVE);
+    }
+#endif
+
+#if IS_ENABLED(CONFIG_ZMK_RGB_UNDERGLOW_AUTO_OFF_USB)
+    if (as_zmk_usb_conn_state_changed(eh)) {
+        static bool prev_state = false;
+        return rgb_underglow_auto_state(&prev_state, zmk_usb_is_powered());
+    }
+#endif
+
+    return -ENOTSUP;
+}
+
+ZMK_LISTENER(rgb_underglow, rgb_underglow_event_listener);
+#endif // IS_ENABLED(CONFIG_ZMK_RGB_UNDERGLOW_AUTO_OFF_IDLE) ||
+       // IS_ENABLED(CONFIG_ZMK_RGB_UNDERGLOW_AUTO_OFF_USB)
+
+#if IS_ENABLED(CONFIG_ZMK_RGB_UNDERGLOW_AUTO_OFF_IDLE)
+ZMK_SUBSCRIPTION(rgb_underglow, zmk_activity_state_changed);
+#endif
+
+#if IS_ENABLED(CONFIG_ZMK_RGB_UNDERGLOW_AUTO_OFF_USB)
+ZMK_SUBSCRIPTION(rgb_underglow, zmk_usb_conn_state_changed);
+#endif
+
 SYS_INIT(zmk_rgb_underglow_init, APPLICATION, CONFIG_APPLICATION_INIT_PRIORITY);