[esp32_ble_tracker] Replace scanner state callback with listener interface (#12156)

esphome/components/bluetooth_proxy/bluetooth_proxy.cpp

@@ -27,11 +27,13 @@ void BluetoothProxy::setup() {
   // Capture the configured scan mode from YAML before any API changes
   this->configured_scan_active_ = this->parent_->get_scan_active();
 
-  this->parent_->add_scanner_state_callback([this](esp32_ble_tracker::ScannerState state) {
-    if (this->api_connection_ != nullptr) {
-      this->send_bluetooth_scanner_state_(state);
-    }
-  });
+  this->parent_->add_scanner_state_listener(this);
+}
+
+void BluetoothProxy::on_scanner_state(esp32_ble_tracker::ScannerState state) {
+  if (this->api_connection_ != nullptr) {
+    this->send_bluetooth_scanner_state_(state);
+  }
 }
 
 void BluetoothProxy::send_bluetooth_scanner_state_(esp32_ble_tracker::ScannerState state) {

esphome/components/bluetooth_proxy/bluetooth_proxy.h

@@ -52,7 +52,9 @@ enum BluetoothProxySubscriptionFlag : uint32_t {
   SUBSCRIPTION_RAW_ADVERTISEMENTS = 1 << 0,
 };
 
-class BluetoothProxy final : public esp32_ble_tracker::ESPBTDeviceListener, public Component {
+class BluetoothProxy final : public esp32_ble_tracker::ESPBTDeviceListener,
+                             public esp32_ble_tracker::BLEScannerStateListener,
+                             public Component {
   friend class BluetoothConnection;  // Allow connection to update connections_free_response_
  public:
   BluetoothProxy();
@@ -108,6 +110,9 @@ class BluetoothProxy final : public esp32_ble_tracker::ESPBTDeviceListener, publ
   void set_active(bool active) { this->active_ = active; }
   bool has_active() { return this->active_; }
 
+  /// BLEScannerStateListener interface
+  void on_scanner_state(esp32_ble_tracker::ScannerState state) override;
+
   uint32_t get_legacy_version() const {
     if (this->active_) {
       return LEGACY_ACTIVE_CONNECTIONS_VERSION;

esphome/components/esp32_ble_tracker/esp32_ble_tracker.cpp

@@ -373,7 +373,9 @@ void ESP32BLETracker::gattc_event_handler(esp_gattc_cb_event_t event, esp_gatt_i
 
 void ESP32BLETracker::set_scanner_state_(ScannerState state) {
   this->scanner_state_ = state;
-  this->scanner_state_callbacks_.call(state);
+  for (auto *listener : this->scanner_state_listeners_) {
+    listener->on_scanner_state(state);
+  }
 }
 
 #ifdef USE_ESP32_BLE_DEVICE

esphome/components/esp32_ble_tracker/esp32_ble_tracker.h

@@ -180,6 +180,16 @@ enum class ScannerState {
   STOPPING,
 };
 
+/** Listener interface for BLE scanner state changes.
+ *
+ * Components can implement this interface to receive scanner state updates
+ * without the overhead of std::function callbacks.
+ */
+class BLEScannerStateListener {
+ public:
+  virtual void on_scanner_state(ScannerState state) = 0;
+};
+
 // Helper function to convert ClientState to string
 const char *client_state_to_string(ClientState state);
 
@@ -264,8 +274,9 @@ class ESP32BLETracker : public Component,
   void gap_scan_event_handler(const BLEScanResult &scan_result) override;
   void ble_before_disabled_event_handler() override;
 
-  void add_scanner_state_callback(std::function<void(ScannerState)> &&callback) {
-    this->scanner_state_callbacks_.add(std::move(callback));
+  /// Add a listener for scanner state changes
+  void add_scanner_state_listener(BLEScannerStateListener *listener) {
+    this->scanner_state_listeners_.push_back(listener);
   }
   ScannerState get_scanner_state() const { return this->scanner_state_; }
 
@@ -322,14 +333,14 @@ class ESP32BLETracker : public Component,
     return counts;
   }
 
-  // Group 1: Large objects (12+ bytes) - vectors and callback manager
+  // Group 1: Large objects (12+ bytes) - vectors
 #ifdef ESPHOME_ESP32_BLE_TRACKER_LISTENER_COUNT
   StaticVector<ESPBTDeviceListener *, ESPHOME_ESP32_BLE_TRACKER_LISTENER_COUNT> listeners_;
 #endif
 #ifdef ESPHOME_ESP32_BLE_TRACKER_CLIENT_COUNT
   StaticVector<ESPBTClient *, ESPHOME_ESP32_BLE_TRACKER_CLIENT_COUNT> clients_;
 #endif
-  CallbackManager<void(ScannerState)> scanner_state_callbacks_;
+  std::vector<BLEScannerStateListener *> scanner_state_listeners_;
 #ifdef USE_ESP32_BLE_DEVICE
   /// Vector of addresses that have already been printed in print_bt_device_info
   std::vector<uint64_t> already_discovered_;