feat(display): Add new peripheral status/display

* Add new API/status to track state of the
  peripheral connection to the central.
* Add new peripheral status widget for displaying
  the current status of the connection to
  the central.

app/CMakeLists.txt

@@ -26,25 +26,19 @@ target_sources(app PRIVATE src/stdlib.c)
 target_sources(app PRIVATE src/activity.c)
 target_sources(app PRIVATE src/kscan.c)
 target_sources(app PRIVATE src/matrix_transform.c)
-target_sources(app PRIVATE src/hid.c)
 target_sources(app PRIVATE src/sensors.c)
 target_sources_ifdef(CONFIG_ZMK_WPM app PRIVATE src/wpm.c)
 target_sources(app PRIVATE src/event_manager.c)
 target_sources_ifdef(CONFIG_ZMK_EXT_POWER app PRIVATE src/ext_power_generic.c)
 target_sources(app PRIVATE src/events/activity_state_changed.c)
 target_sources(app PRIVATE src/events/position_state_changed.c)
-target_sources(app PRIVATE src/events/layer_state_changed.c)
-target_sources(app PRIVATE src/events/keycode_state_changed.c)
-target_sources(app PRIVATE src/events/modifiers_state_changed.c)
-target_sources(app PRIVATE src/events/endpoint_selection_changed.c)
 target_sources(app PRIVATE src/events/sensor_event.c)
 target_sources_ifdef(CONFIG_ZMK_WPM app PRIVATE src/events/wpm_state_changed.c)
-target_sources_ifdef(CONFIG_ZMK_BLE app PRIVATE src/events/ble_active_profile_changed.c)
-target_sources_ifdef(CONFIG_ZMK_BLE app PRIVATE src/events/battery_state_changed.c)
 target_sources_ifdef(CONFIG_USB_DEVICE_STACK app PRIVATE src/events/usb_conn_state_changed.c)
 target_sources(app PRIVATE src/behaviors/behavior_reset.c)
 target_sources_ifdef(CONFIG_ZMK_EXT_POWER app PRIVATE src/behaviors/behavior_ext_power.c)
 if ((NOT CONFIG_ZMK_SPLIT) OR CONFIG_ZMK_SPLIT_BLE_ROLE_CENTRAL)
+  target_sources(app PRIVATE src/hid.c)
   target_sources(app PRIVATE src/behaviors/behavior_key_press.c)
   target_sources(app PRIVATE src/behaviors/behavior_hold_tap.c)
   target_sources(app PRIVATE src/behaviors/behavior_sticky_key.c)
@@ -64,12 +58,16 @@ if ((NOT CONFIG_ZMK_SPLIT) OR CONFIG_ZMK_SPLIT_BLE_ROLE_CENTRAL)
   target_sources(app PRIVATE src/behavior_queue.c)
   target_sources(app PRIVATE src/conditional_layer.c)
   target_sources(app PRIVATE src/endpoints.c)
+  target_sources(app PRIVATE src/events/endpoint_selection_changed.c)
   target_sources(app PRIVATE src/hid_listener.c)
   target_sources(app PRIVATE src/keymap.c)
-
-  target_sources_ifdef(CONFIG_ZMK_BLE app PRIVATE src/behaviors/behavior_bt.c)
+  target_sources(app PRIVATE src/events/layer_state_changed.c)
+  target_sources(app PRIVATE src/events/modifiers_state_changed.c)
+  target_sources(app PRIVATE src/events/keycode_state_changed.c)
 
   if (CONFIG_ZMK_BLE)
+    target_sources(app PRIVATE src/events/ble_active_profile_changed.c)
+    target_sources(app PRIVATE src/behaviors/behavior_bt.c)
     target_sources(app PRIVATE src/ble.c)
     target_sources(app PRIVATE src/hog.c)
   endif()
@@ -77,15 +75,20 @@ endif()
 
 target_sources_ifdef(CONFIG_ZMK_RGB_UNDERGLOW app PRIVATE src/behaviors/behavior_rgb_underglow.c)
 target_sources_ifdef(CONFIG_ZMK_BACKLIGHT app PRIVATE src/behaviors/behavior_backlight.c)
+
+target_sources_ifdef(CONFIG_ZMK_BLE app PRIVATE src/events/battery_state_changed.c)
 target_sources_ifdef(CONFIG_ZMK_BLE app PRIVATE src/battery.c)
 
-if (CONFIG_ZMK_SPLIT_BLE AND (NOT CONFIG_ZMK_SPLIT_BLE_ROLE_CENTRAL))
-  target_sources(app PRIVATE src/split_listener.c)
-  target_sources(app PRIVATE src/split/bluetooth/service.c)
-  target_sources(app PRIVATE src/split/bluetooth/peripheral.c)
-endif()
-if (CONFIG_ZMK_SPLIT_BLE AND CONFIG_ZMK_SPLIT_BLE_ROLE_CENTRAL)
-  target_sources(app PRIVATE src/split/bluetooth/central.c)
+if (CONFIG_ZMK_SPLIT_BLE)
+  if (NOT CONFIG_ZMK_SPLIT_BLE_ROLE_CENTRAL)
+    target_sources(app PRIVATE src/split_listener.c)
+    target_sources(app PRIVATE src/split/bluetooth/service.c)
+    target_sources(app PRIVATE src/split/bluetooth/peripheral.c)
+    target_sources(app PRIVATE src/events/split_peripheral_status_changed.c)
+  endif()
+  if (CONFIG_ZMK_SPLIT_BLE_ROLE_CENTRAL)
+    target_sources(app PRIVATE src/split/bluetooth/central.c)
+  endif()
 endif()
 target_sources_ifdef(CONFIG_USB_DEVICE_STACK app PRIVATE src/usb.c)
 target_sources_ifdef(CONFIG_ZMK_USB app PRIVATE src/usb_hid.c)

app/include/zmk/display/widgets/peripheral_status.h

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2022 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+#include <lvgl.h>
+#include <kernel.h>
+
+struct zmk_widget_peripheral_status {
+    sys_snode_t node;
+    lv_obj_t *obj;
+};
+
+int zmk_widget_peripheral_status_init(struct zmk_widget_peripheral_status *widget,
+                                      lv_obj_t *parent);
+lv_obj_t *zmk_widget_peripheral_status_obj(struct zmk_widget_peripheral_status *widget);

app/include/zmk/events/split_peripheral_status_changed.h

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2022 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+#include <zephyr.h>
+#include <zmk/event_manager.h>
+
+struct zmk_split_peripheral_status_changed {
+    bool connected;
+};
+
+ZMK_EVENT_DECLARE(zmk_split_peripheral_status_changed);

app/include/zmk/split/bluetooth/peripheral.h

@@ -0,0 +1,9 @@
+/*
+ * Copyright (c) 2022 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+bool zmk_split_bt_peripheral_is_connected(void);

app/src/display/status_screen.c

@@ -5,6 +5,7 @@
  */
 
 #include <zmk/display/widgets/output_status.h>
+#include <zmk/display/widgets/peripheral_status.h>
 #include <zmk/display/widgets/battery_status.h>
 #include <zmk/display/widgets/layer_status.h>
 #include <zmk/display/widgets/wpm_status.h>
@@ -21,6 +22,10 @@ static struct zmk_widget_battery_status battery_status_widget;
 static struct zmk_widget_output_status output_status_widget;
 #endif
 
+#if IS_ENABLED(CONFIG_ZMK_WIDGET_PERIPHERAL_STATUS)
+static struct zmk_widget_peripheral_status peripheral_status_widget;
+#endif
+
 #if IS_ENABLED(CONFIG_ZMK_WIDGET_LAYER_STATUS)
 static struct zmk_widget_layer_status layer_status_widget;
 #endif
@@ -46,6 +51,12 @@ lv_obj_t *zmk_display_status_screen() {
                  0);
 #endif
 
+#if IS_ENABLED(CONFIG_ZMK_WIDGET_PERIPHERAL_STATUS)
+    zmk_widget_peripheral_status_init(&peripheral_status_widget, screen);
+    lv_obj_align(zmk_widget_peripheral_status_obj(&peripheral_status_widget), NULL,
+                 LV_ALIGN_IN_TOP_LEFT, 0, 0);
+#endif
+
 #if IS_ENABLED(CONFIG_ZMK_WIDGET_LAYER_STATUS)
     zmk_widget_layer_status_init(&layer_status_widget, screen);
     lv_obj_set_style_local_text_font(zmk_widget_layer_status_obj(&layer_status_widget),

app/src/display/widgets/CMakeLists.txt

@@ -3,5 +3,6 @@
 
 target_sources_ifdef(CONFIG_ZMK_WIDGET_BATTERY_STATUS app PRIVATE battery_status.c)
 target_sources_ifdef(CONFIG_ZMK_WIDGET_OUTPUT_STATUS app PRIVATE output_status.c)
+target_sources_ifdef(CONFIG_ZMK_WIDGET_PERIPHERAL_STATUS app PRIVATE peripheral_status.c)
 target_sources_ifdef(CONFIG_ZMK_WIDGET_LAYER_STATUS app PRIVATE layer_status.c)
 target_sources_ifdef(CONFIG_ZMK_WIDGET_WPM_STATUS app PRIVATE wpm_status.c)

app/src/display/widgets/Kconfig

@@ -17,8 +17,14 @@ config ZMK_WIDGET_BATTERY_STATUS
 
 config ZMK_WIDGET_OUTPUT_STATUS
     bool "Widget for keyboard output status icons"
-    depends on BT
-    default y if BT
+    depends on BT && (!ZMK_SPLIT_BLE || ZMK_SPLIT_BLE_ROLE_CENTRAL)
+    default y if BT && (!ZMK_SPLIT_BLE || ZMK_SPLIT_BLE_ROLE_CENTRAL)
+    select LVGL_USE_LABEL
+
+config ZMK_WIDGET_PERIPHERAL_STATUS
+    bool "Widget for split peripheral status icons"
+    depends on BT && ZMK_SPLIT_BLE && !ZMK_SPLIT_BLE_ROLE_CENTRAL
+    default y if BT && ZMK_SPLIT_BLE && !ZMK_SPLIT_BLE_ROLE_CENTRAL
     select LVGL_USE_LABEL
     
 config ZMK_WIDGET_WPM_STATUS

app/src/display/widgets/peripheral_status.c

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2022 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <kernel.h>
+#include <bluetooth/services/bas.h>
+
+#include <logging/log.h>
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+#include <zmk/display.h>
+#include <zmk/display/widgets/peripheral_status.h>
+#include <zmk/event_manager.h>
+#include <zmk/split/bluetooth/peripheral.h>
+#include <zmk/events/split_peripheral_status_changed.h>
+
+static sys_slist_t widgets = SYS_SLIST_STATIC_INIT(&widgets);
+
+struct peripheral_status_state {
+    bool connected;
+};
+
+static struct peripheral_status_state get_state(const zmk_event_t *_eh) {
+    return (struct peripheral_status_state){.connected = zmk_split_bt_peripheral_is_connected()};
+}
+
+static void set_status_symbol(lv_obj_t *label, struct peripheral_status_state state) {
+    const char *text =
+        state.connected ? (LV_SYMBOL_WIFI " " LV_SYMBOL_OK) : (LV_SYMBOL_WIFI " " LV_SYMBOL_CLOSE);
+
+    LOG_DBG("connected? %s", state.connected ? "true" : "false");
+    lv_label_set_text(label, text);
+}
+
+static void output_status_update_cb(struct peripheral_status_state state) {
+    struct zmk_widget_peripheral_status *widget;
+    SYS_SLIST_FOR_EACH_CONTAINER(&widgets, widget, node) { set_status_symbol(widget->obj, state); }
+}
+
+ZMK_DISPLAY_WIDGET_LISTENER(widget_peripheral_status, struct peripheral_status_state,
+                            output_status_update_cb, get_state)
+ZMK_SUBSCRIPTION(widget_peripheral_status, zmk_split_peripheral_status_changed);
+
+int zmk_widget_peripheral_status_init(struct zmk_widget_peripheral_status *widget,
+                                      lv_obj_t *parent) {
+    widget->obj = lv_label_create(parent, NULL);
+
+    lv_obj_set_size(widget->obj, 40, 15);
+
+    sys_slist_append(&widgets, &widget->node);
+
+    widget_peripheral_status_init();
+    return 0;
+}
+
+lv_obj_t *zmk_widget_peripheral_status_obj(struct zmk_widget_peripheral_status *widget) {
+    return widget->obj;
+}

app/src/events/split_peripheral_status_changed.c

@@ -0,0 +1,10 @@
+/*
+ * Copyright (c) 2022 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <kernel.h>
+#include <zmk/events/split_peripheral_status_changed.h>
+
+ZMK_EVENT_IMPL(zmk_split_peripheral_status_changed);

app/src/split/bluetooth/peripheral.c

@@ -30,6 +30,8 @@
 
 LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
 
+#include <zmk/event_manager.h>
+#include <zmk/events/split_peripheral_status_changed.h>
 #include <zmk/ble.h>
 #include <zmk/split/bluetooth/uuid.h>
 
@@ -39,16 +41,30 @@ static const struct bt_data zmk_ble_ad[] = {
                   ),
     BT_DATA_BYTES(BT_DATA_UUID128_ALL, ZMK_SPLIT_BT_SERVICE_UUID)};
 
+static bool is_connected = false;
+
 static int start_advertising() {
     return bt_le_adv_start(BT_LE_ADV_CONN, zmk_ble_ad, ARRAY_SIZE(zmk_ble_ad), NULL, 0);
 };
 
+static void connected(struct bt_conn *conn, uint8_t err) {
+    is_connected = (err == 0);
+
+    ZMK_EVENT_RAISE(new_zmk_split_peripheral_status_changed(
+        (struct zmk_split_peripheral_status_changed){.connected = is_connected}));
+}
+
 static void disconnected(struct bt_conn *conn, uint8_t reason) {
     char addr[BT_ADDR_LE_STR_LEN];
 
     bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));
 
     LOG_DBG("Disconnected from %s (reason 0x%02x)", log_strdup(addr), reason);
+
+    is_connected = false;
+
+    ZMK_EVENT_RAISE(new_zmk_split_peripheral_status_changed(
+        (struct zmk_split_peripheral_status_changed){.connected = is_connected}));
 }
 
 static void security_changed(struct bt_conn *conn, bt_security_t level, enum bt_security_err err) {
@@ -73,11 +89,14 @@ static void le_param_updated(struct bt_conn *conn, uint16_t interval, uint16_t l
 }
 
 static struct bt_conn_cb conn_callbacks = {
+    .connected = connected,
     .disconnected = disconnected,
     .security_changed = security_changed,
     .le_param_updated = le_param_updated,
 };
 
+bool zmk_split_bt_peripheral_is_connected() { return is_connected; }
+
 static int zmk_peripheral_ble_init(const struct device *_arg) {
     int err = bt_enable(NULL);