feat(windows): use ConnectionPriority for preferred connection parameters

gap_windows.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"sync"
 	"unsafe"
 
 	"github.com/go-ole/go-ole"
@@ -295,6 +296,28 @@ type Device struct {
 	session                       *genericattributeprofile.GattSession
 	connectionStatusListenerToken foundation.EventRegistrationToken
 	connectionStatusListener      *foundation.TypedEventHandler
+	connParams                    *connectionParamsState
+}
+
+// connectionParamsState keeps the open connection parameters request.
+// Windows applies the request only while the object is open:
+// https://learn.microsoft.com/en-us/uwp/api/windows.devices.bluetooth.bluetoothledevice.requestpreferredconnectionparameters
+type connectionParamsState struct {
+	mu      sync.Mutex
+	request *bluetooth.BluetoothLEPreferredConnectionParametersRequest
+}
+
+// replace closes the open request and then keeps the new one.
+// A nil request only closes the open request and restores the system defaults.
+func (s *connectionParamsState) replace(request *bluetooth.BluetoothLEPreferredConnectionParametersRequest) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	if s.request != nil {
+		_ = s.request.Close()
+		s.request.Release()
+	}
+	s.request = request
 }
 
 // Connect starts a connection attempt to the given peripheral device address.
@@ -367,8 +390,9 @@ func (a *Adapter) Connect(address Address, params ConnectionParams) (Device, err
 
 		Address: address,
 
-		device:  bleDevice,
-		session: newSession,
+		device:     bleDevice,
+		session:    newSession,
+		connParams: &connectionParamsState{},
 	}
 
 	// https://learn.microsoft.com/es-es/uwp/api/windows.devices.bluetooth.bluetoothledevice.connectionstatuschanged?view=winrt-26100
@@ -417,6 +441,11 @@ func (d Device) Disconnect() error {
 
 	d.cancel()
 
+	// Close the request while the device is still open.
+	if d.connParams != nil {
+		d.connParams.replace(nil)
+	}
+
 	if err := d.session.Close(); err != nil {
 		return err
 	}
@@ -447,13 +476,89 @@ func (d Device) Connected() (bool, error) {
 // Whether or not the device will actually honor this, depends on the device and
 // on the specific parameters.
 //
-// On Windows, this call doesn't do anything.
+// Windows uses only ConnectionParams.Priority. It ignores MinInterval,
+// MaxInterval and Timeout. It needs Windows 11 build 22000 or later.
 func (d Device) RequestConnectionParams(params ConnectionParams) error {
-	// TODO: implement this using
-	// BluetoothLEDevice.RequestPreferredConnectionParameters.
+	if params.Priority == ConnectionPriorityUnspecified {
+		return nil
+	}
+	if d.device == nil || d.connParams == nil {
+		return errors.New("bluetooth: device is not connected")
+	}
+
+	preferred, err := preferredConnectionParameters(params.Priority)
+	if err != nil {
+		return err
+	}
+	defer preferred.Release()
+
+	request, err := d.device.RequestPreferredConnectionParameters(preferred)
+	if err != nil {
+		return err
+	}
+
+	// The status shows only that the system accepted the request. The agreed
+	// parameters come later, in the ConnectionParametersChanged event.
+	status, err := request.GetStatus()
+	if err != nil {
+		discardConnectionParamsRequest(request)
+		return err
+	}
+	if status != bluetooth.BluetoothLEPreferredConnectionParametersRequestStatusSuccess {
+		discardConnectionParamsRequest(request)
+		return fmt.Errorf("bluetooth: connection parameters request was not accepted: %s",
+			connectionParamsRequestStatusString(status))
+	}
+
+	// Keep the request. Windows applies it only while the object is open.
+	d.connParams.replace(request)
+
 	return nil
 }
 
+// preferredConnectionParameters returns the Windows preset for the priority.
+// The caller must release the result.
+func preferredConnectionParameters(priority ConnectionPriority) (*bluetooth.BluetoothLEPreferredConnectionParameters, error) {
+	var (
+		preferred *bluetooth.BluetoothLEPreferredConnectionParameters
+		err       error
+	)
+	switch priority {
+	case ConnectionPriorityThroughput:
+		preferred, err = bluetooth.BluetoothLEPreferredConnectionParametersGetThroughputOptimized()
+	case ConnectionPriorityBalanced:
+		preferred, err = bluetooth.BluetoothLEPreferredConnectionParametersGetBalanced()
+	case ConnectionPriorityPowerSaving:
+		preferred, err = bluetooth.BluetoothLEPreferredConnectionParametersGetPowerOptimized()
+	default:
+		return nil, fmt.Errorf("bluetooth: unknown connection priority %d", priority)
+	}
+	if err != nil {
+		// Windows 10 does not have the activation factory for these presets.
+		return nil, fmt.Errorf("bluetooth: connection priorities need Windows 11 build 22000 or later: %w", err)
+	}
+	return preferred, nil
+}
+
+// discardConnectionParamsRequest closes a request that the device does not keep.
+func discardConnectionParamsRequest(request *bluetooth.BluetoothLEPreferredConnectionParametersRequest) {
+	_ = request.Close()
+	request.Release()
+}
+
+func connectionParamsRequestStatusString(status bluetooth.BluetoothLEPreferredConnectionParametersRequestStatus) string {
+	switch status {
+	case bluetooth.BluetoothLEPreferredConnectionParametersRequestStatusSuccess:
+		return "success"
+	case bluetooth.BluetoothLEPreferredConnectionParametersRequestStatusDeviceNotAvailable:
+		return "device not available"
+	case bluetooth.BluetoothLEPreferredConnectionParametersRequestStatusAccessDenied:
+		return "access denied"
+	default:
+		return "unspecified"
+	}
+}
+
 // SetRandomAddress sets the random address to be used for advertising.
 func (a *Adapter) SetRandomAddress(mac MAC) error {
 	return errors.ErrUnsupported

go.mod

@@ -5,7 +5,7 @@ go 1.22.1
 require (
 	github.com/go-ole/go-ole v1.2.6
 	github.com/godbus/dbus/v5 v5.1.0
-	github.com/saltosystems/winrt-go v0.0.0-20240509164145-4f7860a3bd2b
+	github.com/saltosystems/winrt-go v0.0.0-20260513072510-45f10383b2b8
 	github.com/soypat/cyw43439 v0.0.0-20250505012923-830110c8f4af
 	github.com/tinygo-org/cbgo v0.0.4
 	golang.org/x/crypto v0.12.0

go.sum

@@ -12,6 +12,8 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/saltosystems/winrt-go v0.0.0-20240509164145-4f7860a3bd2b h1:du3zG5fd8snsFN6RBoLA7fpaYV9ZQIsyH9snlk2Zvik=
 github.com/saltosystems/winrt-go v0.0.0-20240509164145-4f7860a3bd2b/go.mod h1:CIltaIm7qaANUIvzr0Vmz71lmQMAIbGJ7cvgzX7FMfA=
+github.com/saltosystems/winrt-go v0.0.0-20260513072510-45f10383b2b8 h1:CpUxfPAWwKKHDCH8tKBzAe6lC3c2mDVspXPP10Z+4IQ=
+github.com/saltosystems/winrt-go v0.0.0-20260513072510-45f10383b2b8/go.mod h1:CIltaIm7qaANUIvzr0Vmz71lmQMAIbGJ7cvgzX7FMfA=
 github.com/sirupsen/logrus v1.5.0/go.mod h1:+F7Ogzej0PZc/94MaYx/nvG9jOFMD2osvC3s+Squfpo=
 github.com/sirupsen/logrus v1.9.3 h1:dueUQJ1C2q9oE3F7wvmSGAaVtTmUizReu6fjN8uqzbQ=
 github.com/sirupsen/logrus v1.9.3/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=