Move connecting to a LE device to background on Windows

The BT LE connectToDevice() method on Windows was a synchronous
operation for the caller by blocking while spinning the event loop
to keep rest of the application responsive.

Other platforms behave differently. This commit makes the connect
call to return immediately while scheduling the connection in the
background.

The QTBUG-83633 was originally about slightly different crash which
seems not be reproducible anymore, but this crash was found while
investigating that and is investigated in that item.

Task-number: QTBUG-83633
Change-Id: I092a94f2437351d27da758db6746f5b24d5fa9c7
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>
(cherry picked from commit 3fc3716e0cd209cd9475d632925a9148b40b2f1d)
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

4 files changed, 23 insertions, 4 deletions

diff --git a/src/bluetooth/qlowenergycontroller_winrt.cpp b/src/bluetooth/qlowenergycontroller_winrt.cpp
index a9f9fd64..6a039337 100644
--- a/src/bluetooth/qlowenergycontroller_winrt.cpp
+++ b/src/bluetooth/qlowenergycontroller_winrt.cpp
@@ -260,14 +260,22 @@ void QLowEnergyControllerPrivateWinRT::init()
 void QLowEnergyControllerPrivateWinRT::connectToDevice()
 {
     qCDebug(QT_BT_WINRT) << __FUNCTION__;
-    Q_Q(QLowEnergyController);
     if (remoteDevice.isNull()) {
         qWarning() << "Invalid/null remote device address";
         setError(QLowEnergyController::UnknownRemoteDeviceError);
         return;
     }
-
     setState(QLowEnergyController::ConnectingState);
+    // Queue the device connecting to happen in the background
+    QMetaObject::invokeMethod(this,
+                          &QLowEnergyControllerPrivateWinRT::doConnectToDevice,
+                          Qt::QueuedConnection);
+}
+
+void QLowEnergyControllerPrivateWinRT::doConnectToDevice()
+{
+    qCDebug(QT_BT_WINRT) << __FUNCTION__;
+    Q_Q(QLowEnergyController);
 
     ComPtr<IBluetoothLEDeviceStatics> deviceStatics;
     HRESULT hr = GetActivationFactory(HString::MakeReference(RuntimeClass_Windows_Devices_Bluetooth_BluetoothLEDevice).Get(), &deviceStatics);
diff --git a/src/bluetooth/qlowenergycontroller_winrt_new.cpp b/src/bluetooth/qlowenergycontroller_winrt_new.cpp
index 9fa86e05..f448fe33 100644
--- a/src/bluetooth/qlowenergycontroller_winrt_new.cpp
+++ b/src/bluetooth/qlowenergycontroller_winrt_new.cpp
@@ -459,14 +459,23 @@ void QLowEnergyControllerPrivateWinRTNew::connectToDevice()
 {
     qCDebug(QT_BT_WINRT) << __FUNCTION__;
     mAbortPending = false;
-    Q_Q(QLowEnergyController);
     if (remoteDevice.isNull()) {
         qWarning() << "Invalid/null remote device address";
         setError(QLowEnergyController::UnknownRemoteDeviceError);
         return;
     }
-
     setState(QLowEnergyController::ConnectingState);
+    // Queue the device connecting to happen in the background
+    QMetaObject::invokeMethod(this,
+                          &QLowEnergyControllerPrivateWinRTNew::doConnectToDevice,
+                          Qt::QueuedConnection);
+}
+
+
+void QLowEnergyControllerPrivateWinRTNew::doConnectToDevice()
+{
+    qCDebug(QT_BT_WINRT) << __FUNCTION__;
+    Q_Q(QLowEnergyController);
 
     ComPtr<IBluetoothLEDeviceStatics> deviceStatics;
     HRESULT hr = GetActivationFactory(
diff --git a/src/bluetooth/qlowenergycontroller_winrt_new_p.h b/src/bluetooth/qlowenergycontroller_winrt_new_p.h
index d7d90dbd..b238f48e 100644
--- a/src/bluetooth/qlowenergycontroller_winrt_new_p.h
+++ b/src/bluetooth/qlowenergycontroller_winrt_new_p.h
@@ -136,6 +136,7 @@ signals:
 private slots:
     void handleCharacteristicChanged(quint16 charHandle, const QByteArray &data);
     void handleServiceHandlerError(const QString &error);
+    void doConnectToDevice();
 
 private:
     void connectToPairedDevice();
diff --git a/src/bluetooth/qlowenergycontroller_winrt_p.h b/src/bluetooth/qlowenergycontroller_winrt_p.h
index d87477c6..629f62fc 100644
--- a/src/bluetooth/qlowenergycontroller_winrt_p.h
+++ b/src/bluetooth/qlowenergycontroller_winrt_p.h
@@ -119,6 +119,7 @@ signals:
 
 private slots:
     void handleCharacteristicChanged(quint16 charHandle, const QByteArray &data);
+    void doConnectToDevice();
 
 private:
     Microsoft::WRL::ComPtr<ABI::Windows::Devices::Bluetooth::IBluetoothLEDevice> mDevice;