winrt: Unload camera when application is suspended.

Camera needs to be unloaded when going to suspend. Otherwise resume from
suspend will hang and application will be terminated.

Change-Id: Idc8bd47e56c99ebd53a1a4632338cf977317a495
Task-Id: QTBUG-48569
Reviewed-by: Andrew Knight <andrew.knight@intopalo.com>

src/plugins/winrt/qwinrtcameracontrol.cpp

@@ -43,8 +43,8 @@
 #include "qwinrtcameralockscontrol.h"
 
 #include <QtCore/qfunctions_winrt.h>
-#include <QtCore/QCoreApplication>
 #include <QtCore/QPointer>
+#include <QtGui/QGuiApplication>
 
 #include <mfapi.h>
 #include <mferror.h>
@@ -547,6 +547,11 @@ QWinRTCameraControl::QWinRTCameraControl(QObject *parent)
     d->imageEncoderControl = new QWinRTImageEncoderControl(this);
     d->cameraFocusControl = new QWinRTCameraFocusControl(this);
     d->cameraLocksControl = new QWinRTCameraLocksControl(this);
+
+    if (qGuiApp) {
+        connect(qGuiApp, &QGuiApplication::applicationStateChanged,
+                this, &QWinRTCameraControl::onApplicationStateChanged);
+    }
 }
 
 QWinRTCameraControl::~QWinRTCameraControl()
@@ -778,6 +783,25 @@ void QWinRTCameraControl::onBufferRequested()
         d->mediaSink->RequestSample();
 }
 
+void QWinRTCameraControl::onApplicationStateChanged(Qt::ApplicationState state)
+{
+    Q_D(QWinRTCameraControl);
+    static QCamera::State savedState = d->state;
+    switch (state) {
+    case Qt::ApplicationInactive:
+        if (d->state != QCamera::UnloadedState) {
+            savedState = d->state;
+            setState(QCamera::UnloadedState);
+        }
+        break;
+    case Qt::ApplicationActive:
+        setState(QCamera::State(savedState));
+        break;
+    default:
+        break;
+    }
+}
+
 HRESULT QWinRTCameraControl::initialize()
 {
     Q_D(QWinRTCameraControl);

src/plugins/winrt/qwinrtcameracontrol.h

@@ -104,6 +104,7 @@ public:
 
 private slots:
     void onBufferRequested();
+    void onApplicationStateChanged(Qt::ApplicationState state);
 
 private:
     HRESULT enumerateDevices();