winrt: Prevent camera device from being suspended.

On certain Lumia devices video buffer gets page locked when camera
is stopped. Subsequent call to video frame map/unmap leads to camera
device suspension. As a fix delay camera unload until all mapped
video frames are unmapped and return early from video frame map when
camera is not active.

Task-Id: QTBUG-48672
Change-Id: If547b9d430727bbe0e12cd8c07a30aeff81d13e3
Reviewed-by: Andrew Knight <andrew.knight@intopalo.com>

src/plugins/winrt/qwinrtcameracontrol.cpp

@@ -524,6 +524,8 @@ public:
     QPointer<QWinRTImageEncoderControl> imageEncoderControl;
     QPointer<QWinRTCameraFocusControl> cameraFocusControl;
     QPointer<QWinRTCameraLocksControl> cameraLocksControl;
+    QAtomicInt framesMapped;
+    QEventLoop *delayClose;
 };
 
 QWinRTCameraControl::QWinRTCameraControl(QObject *parent)
@@ -531,6 +533,7 @@ QWinRTCameraControl::QWinRTCameraControl(QObject *parent)
 {
     Q_D(QWinRTCameraControl);
 
+    d->delayClose = nullptr;
     d->state = QCamera::UnloadedState;
     d->status = QCamera::UnloadedStatus;
     d->captureMode = QCamera::CaptureStillImage;
@@ -612,6 +615,14 @@ void QWinRTCameraControl::setState(QCamera::State state)
     case QCamera::UnloadedState: {
         // Stop the camera if it is running (transition to LoadedState)
         if (d->status == QCamera::ActiveStatus) {
+            if (d->framesMapped > 0) {
+                qWarning("%d QVideoFrame(s) mapped when closing down camera. Camera will wait for unmap before closing down.",
+                         d->framesMapped);
+                if (!d->delayClose)
+                    d->delayClose = new QEventLoop(this);
+                d->delayClose->exec();
+            }
+
             ComPtr<IAsyncAction> op;
             hr = d->capturePreview->StopPreviewAsync(&op);
             RETURN_VOID_AND_EMIT_ERROR("Failed to stop camera preview");
@@ -1208,6 +1219,21 @@ bool QWinRTCameraControl::unlockFocus()
 
 #endif // !Q_OS_WINPHONE
 
+void QWinRTCameraControl::frameMapped()
+{
+    Q_D(QWinRTCameraControl);
+    ++d->framesMapped;
+}
+
+void QWinRTCameraControl::frameUnmapped()
+{
+    Q_D(QWinRTCameraControl);
+    --d->framesMapped;
+    Q_ASSERT(d->framesMapped >= 0);
+    if (!d->framesMapped && d->delayClose && d->delayClose->isRunning())
+        d->delayClose->exit();
+}
+
 HRESULT QWinRTCameraControl::onCaptureFailed(IMediaCapture *, IMediaCaptureFailedEventArgs *args)
 {
     HRESULT hr;

src/plugins/winrt/qwinrtcameracontrol.h

@@ -99,6 +99,8 @@ public:
     void emitError(int errorCode, const QString &errorString);
     bool lockFocus();
     bool unlockFocus();
+    void frameMapped();
+    void frameUnmapped();
 
 private slots:
     void onBufferRequested();

src/plugins/winrt/qwinrtcameravideorenderercontrol.cpp

@@ -38,6 +38,7 @@
 
 #include <QtCore/qfunctions_winrt.h>
 #include <QtCore/QSize>
+#include <QtCore/QPointer>
 #include <QtCore/QVector>
 #include <QVideoFrame>
 
@@ -45,6 +46,8 @@
 #include <mfapi.h>
 #include <wrl.h>
 
+#include "qwinrtcameracontrol.h"
+
 #ifdef Q_OS_WINPHONE
 #include <Windows.Security.ExchangeActiveSyncProvisioning.h>
 using namespace ABI::Windows::Security::ExchangeActiveSyncProvisioning;
@@ -68,12 +71,14 @@ static bool blacklisted(const wchar_t (&blackListName)[n], const HString &device
 class QWinRTCameraVideoBuffer : public QAbstractVideoBuffer
 {
 public:
-    QWinRTCameraVideoBuffer(IMF2DBuffer *buffer, int size)
+    QWinRTCameraVideoBuffer(IMF2DBuffer *buffer, int size, QWinRTCameraControl *control)
         : QAbstractVideoBuffer(NoHandle)
         , currentMode(NotMapped)
         , buffer(buffer)
         , size(size)
+        , control(control)
     {
+        Q_ASSERT(control);
     }
 
     ~QWinRTCameraVideoBuffer()
@@ -88,13 +93,14 @@ public:
 
     uchar *map(MapMode mode, int *numBytes, int *bytesPerLine) Q_DECL_OVERRIDE
     {
-        if (currentMode != NotMapped || mode == NotMapped)
+        if (currentMode != NotMapped || mode == NotMapped || control && control->state() != QCamera::ActiveState)
             return nullptr;
 
         BYTE *bytes;
         LONG stride;
         HRESULT hr = buffer->Lock2D(&bytes, &stride);
         RETURN_IF_FAILED("Failed to lock camera frame buffer", nullptr);
+        control->frameMapped();
 
         if (bytesPerLine)
             *bytesPerLine = stride;
@@ -111,12 +117,15 @@ public:
         HRESULT hr = buffer->Unlock2D();
         RETURN_VOID_IF_FAILED("Failed to unlock camera frame buffer");
         currentMode = NotMapped;
+        if (control)
+            control->frameUnmapped();
     }
 
 private:
     ComPtr<IMF2DBuffer> buffer;
     MapMode currentMode;
     int size;
+    QPointer<QWinRTCameraControl> control;
 };
 
 class D3DVideoBlitter
@@ -331,7 +340,9 @@ bool QWinRTCameraVideoRendererControl::dequeueFrame(QVideoFrame *frame)
         return false;
     }
 
-    QWinRTCameraVideoBuffer *videoBuffer = new QWinRTCameraVideoBuffer(buffer.Get(), d->cameraSampleSize);
+    QWinRTCameraVideoBuffer *videoBuffer = new QWinRTCameraVideoBuffer(buffer.Get(),
+                                                                       d->cameraSampleSize,
+                                                                       static_cast<QWinRTCameraControl *>(parent()));
     *frame = QVideoFrame(videoBuffer, size(), d->cameraSampleformat);
 
     emit bufferRequested();
@@ -350,7 +361,9 @@ void QWinRTCameraVideoRendererControl::queueBuffer(IMF2DBuffer *buffer)
     }
 
     if (d->videoProbesCounter > 0 && d->cameraSampleformat != QVideoFrame::Format_Invalid) {
-        QWinRTCameraVideoBuffer *videoBuffer = new QWinRTCameraVideoBuffer(buffer, d->cameraSampleSize);
+        QWinRTCameraVideoBuffer *videoBuffer = new QWinRTCameraVideoBuffer(buffer,
+                                                                           d->cameraSampleSize,
+                                                                           static_cast<QWinRTCameraControl *>(parent()));
         QVideoFrame frame(videoBuffer, size(), d->cameraSampleformat);
         emit videoFrameProbed(frame);
     }