fix(winrt): prefer notifications and retain connection parameter requests

src/winrtble/ble/device.rs

@@ -19,7 +19,7 @@ use tokio::time::timeout;
 use windows::{
     Devices::Bluetooth::{
         BluetoothCacheMode, BluetoothConnectionStatus, BluetoothLEDevice,
-        BluetoothLEPreferredConnectionParameters,
+        BluetoothLEPreferredConnectionParameters, BluetoothLEPreferredConnectionParametersRequest,
         GenericAttributeProfile::{
             GattCharacteristic, GattCommunicationStatus, GattDescriptor, GattDeviceService,
             GattDeviceServicesResult, GattSession,
@@ -41,6 +41,7 @@ pub struct BLEDevice {
     connection_token: i64,
     pdu_change_token: i64,
     services: Vec<GattDeviceService>,
+    preferred_parameters_request: Option<BluetoothLEPreferredConnectionParametersRequest>,
 }
 
 impl BLEDevice {
@@ -89,6 +90,7 @@ impl BLEDevice {
             connection_token,
             pdu_change_token,
             services: vec![],
+            preferred_parameters_request: None,
         })
     }
 
@@ -220,7 +222,7 @@ impl BLEDevice {
     }
 
     pub fn request_connection_parameters(
-        &self,
+        &mut self,
         preset: crate::api::ConnectionParameterPreset,
     ) -> Result<()> {
         let winrt_error = |e| Error::Other(format!("{:?}", e).into());
@@ -244,7 +246,12 @@ impl BLEDevice {
         // BluetoothLEPreferredConnectionParametersRequestStatus:
         //   Unspecified = 0, Success = 1, DeviceNotAvailable = 2, AccessDenied = 3
         match status.0 {
-            1 => Ok(()),
+            1 => {
+                if let Some(previous) = self.preferred_parameters_request.replace(result) {
+                    let _ = previous.Close();
+                }
+                Ok(())
+            }
             2 | 3 => Err(Error::NotSupported(format!(
                 "request_connection_parameters not supported (status {:?})",
                 status
@@ -273,13 +280,20 @@ impl BLEDevice {
                 .collect();
             self.services = services;
             debug!("services {:?}", self.services.len());
+        } else {
+            // Do not turn an unreachable/protocol failure into an empty service
+            // list and a misleading "missing characteristic" error in callers.
+            utils::to_error(status)?;
         }
         Ok(self.services.as_slice())
     }
 }
 
 impl Drop for BLEDevice {
     fn drop(&mut self) {
+        if let Some(request) = self.preferred_parameters_request.take() {
+            let _ = request.Close();
+        }
         let result = self
             .gatt_session
             .RemoveMaxPduSizeChanged(self.pdu_change_token);

src/winrtble/peripheral.rs

@@ -721,8 +721,8 @@ impl ApiPeripheral for Peripheral {
     }
 
     async fn request_connection_parameters(&self, preset: ConnectionParameterPreset) -> Result<()> {
-        let device = self.shared.device.lock().await;
-        match &*device {
+        let mut device = self.shared.device.lock().await;
+        match &mut *device {
             Some(device) => device.request_connection_parameters(preset),
             None => Err(Error::NotConnected),
         }

src/winrtble/utils.rs

@@ -42,15 +42,41 @@ pub fn to_descriptor_value(
 ) -> GattClientCharacteristicConfigurationDescriptorValue {
     let notify = GattCharacteristicProperties::Notify;
     let indicate = GattCharacteristicProperties::Indicate;
-    if properties & indicate == indicate {
-        GattClientCharacteristicConfigurationDescriptorValue::Indicate
-    } else if properties & notify == notify {
+    if properties & notify == notify {
         GattClientCharacteristicConfigurationDescriptorValue::Notify
+    } else if properties & indicate == indicate {
+        GattClientCharacteristicConfigurationDescriptorValue::Indicate
     } else {
         GattClientCharacteristicConfigurationDescriptorValue::None
     }
 }
 
+#[cfg(test)]
+mod notification_mode_tests {
+    use super::*;
+    #[test]
+    fn prefer_notifications_when_both_modes_are_advertised() {
+        let notify = GattCharacteristicProperties::Notify;
+        let indicate = GattCharacteristicProperties::Indicate;
+        assert_eq!(
+            to_descriptor_value(notify | indicate),
+            GattClientCharacteristicConfigurationDescriptorValue::Notify
+        );
+        assert_eq!(
+            to_descriptor_value(notify),
+            GattClientCharacteristicConfigurationDescriptorValue::Notify
+        );
+        assert_eq!(
+            to_descriptor_value(indicate),
+            GattClientCharacteristicConfigurationDescriptorValue::Indicate
+        );
+        assert_eq!(
+            to_descriptor_value(GattCharacteristicProperties::None),
+            GattClientCharacteristicConfigurationDescriptorValue::None
+        );
+    }
+}
+
 pub fn to_uuid(uuid: &GUID) -> Uuid {
     let guid_s = format!("{:?}", uuid);
     Uuid::from_str(&guid_s).unwrap()