Experimental: Add layer indicator

Kconfig

@@ -30,4 +30,11 @@ config RGBLED_WIDGET_BATTERY_LEVEL_CRITICAL
     int "Critical battery level percentage"
     default 5
 
+config RGBLED_WIDGET_SHOW_LAYER_CHANGE
+    bool "Indicate highest active layer on each layer change with a sequence of blinks"
+
+config RGBLED_WIDGET_LAYER_BLINK_MS
+    int "Blink and wait duration for layer indicator"
+    default 100
+
 endif

README.md

@@ -46,11 +46,16 @@ For other keyboards, see the "Adding support" section below.
 See [this video](https://cdn.discordapp.com/attachments/1134635625455292426/1134639930501496832/rgbled_widget.mp4) for a short demo, running through power on, profile switching and power offs.
 
 Currently the widget does the following:
+
 - Blink 🟢/🟡/🔴 on boot depending on battery level (for both central/peripherals), thresholds set by `CONFIG_RGBLED_WIDGET_BATTERY_LEVEL_HIGH` and `CONFIG_RGBLED_WIDGET_BATTERY_LEVEL_LOW`
 - Blink 🔴 on every battery level change if below critical battery level (`CONFIG_RGBLED_WIDGET_BATTERY_LEVEL_CRITICAL`)
 - Blink 🔵 for connected, 🟡 for open (advertising), 🔴 for disconnected profiles on every BT profile switch (on central side for splits)
 - Blink 🔵 for connected, 🔴 for disconnected on peripheral side of splits
 
+_Experimental_: Enable `CONFIG_RGBLED_WIDGET_SHOW_LAYER_CHANGE` to show the highest active layer on every layer change
+using a sequence of N cyan color blinks, where N is the zero-based index of the layer.
+Note that this can be noisy and distracting, especially if you use conditional layers.
+
 ## Configuration
 
 Blink durations can also be adjusted, see the [Kconfig file](Kconfig) for available config properties.
@@ -64,7 +69,7 @@ CONFIG_RGBLED_WIDGET_BATTERY_LEVEL_CRITICAL=10
 
 ## Adding support in custom boards/shields
 
-To be able to use this widget, you need three LEDs controlled by GPIOs (*not* smart LEDs), ideally red, green and blue colors.
+To be able to use this widget, you need three LEDs controlled by GPIOs (_not_ smart LEDs), ideally red, green and blue colors.
 Once you have these LED definitions in your board/shield, simply set the appropriate `aliases` to the RGB LED node labels.
 
 As an example, here is a definition for three LEDs connected to GND and separate GPIOs for a nRF52840 controller:

leds.c

@@ -7,10 +7,12 @@
 
 #include <zmk/ble.h>
 #include <zmk/endpoints.h>
+#include <zmk/keymap.h>
 #include <zmk/events/ble_active_profile_changed.h>
 #include <zmk/split/bluetooth/peripheral.h>
 #include <zmk/events/split_peripheral_status_changed.h>
 #include <zmk/events/battery_state_changed.h>
+#include <zmk/events/layer_state_changed.h>
 
 #include <zephyr/logging/log.h>
 
@@ -45,6 +47,7 @@ struct blink_item {
     enum color_t color;
     uint16_t duration_ms;
     bool first_item;
+    uint16_t sleep_ms;
 };
 
 // define message queue of blink work items, that will be processed by a separate thread
@@ -112,6 +115,35 @@ ZMK_LISTENER(led_battery_listener, led_battery_listener_cb);
 ZMK_SUBSCRIPTION(led_battery_listener, zmk_battery_state_changed);
 #endif // IS_ENABLED(CONFIG_ZMK_BATTERY_REPORTING)
 
+#if IS_ENABLED(CONFIG_RGBLED_WIDGET_SHOW_LAYER_CHANGE)
+#if !IS_ENABLED(CONFIG_ZMK_SPLIT) || IS_ENABLED(CONFIG_ZMK_SPLIT_ROLE_CENTRAL)
+static int led_layer_listener_cb(const zmk_event_t *eh) {
+    // ignore layer off events
+    if (!((struct zmk_layer_state_changed *)eh)->state) {
+        return 0;
+    }
+
+    uint8_t index = zmk_keymap_highest_layer_active();
+    static const struct blink_item blink = {.duration_ms = CONFIG_RGBLED_WIDGET_LAYER_BLINK_MS,
+                                            .color = LED_CYAN,
+                                            .sleep_ms = CONFIG_RGBLED_WIDGET_LAYER_BLINK_MS};
+    static const struct blink_item last_blink = {.duration_ms = CONFIG_RGBLED_WIDGET_LAYER_BLINK_MS,
+                                                 .color = LED_CYAN};
+    for (int i = 0; i < index; i++) {
+        if (i < index - 1) {
+            k_msgq_put(&led_msgq, &blink, K_NO_WAIT);
+        } else {
+            k_msgq_put(&led_msgq, &last_blink, K_NO_WAIT);
+        }
+    }
+    return 0;
+}
+
+ZMK_LISTENER(led_layer_listener, led_layer_listener_cb);
+ZMK_SUBSCRIPTION(led_layer_listener, zmk_layer_state_changed);
+#endif
+#endif // IS_ENABLED(CONFIG_RGBLED_WIDGET_SHOW_LAYER_CHANGE)
+
 extern void led_thread(void *d0, void *d1, void *d2) {
     ARG_UNUSED(d0);
     ARG_UNUSED(d1);
@@ -176,7 +208,11 @@ extern void led_thread(void *d0, void *d1, void *d2) {
         }
 
         // wait interval before processing another blink
-        k_sleep(K_MSEC(CONFIG_RGBLED_WIDGET_INTERVAL_MS));
+        if (blink.sleep_ms > 0) {
+            k_sleep(K_MSEC(blink.sleep_ms));
+        } else {
+            k_sleep(K_MSEC(CONFIG_RGBLED_WIDGET_INTERVAL_MS));
+        }
     }
 }