winrt: Use QMutex instead of criticalSections

critical sections are really unpredictable when it
comes to order of activation. It was possible that
the loop in QWinRTAbstractVideoRendererControl's
syncAndRender blocked its setBlitMode for up to 30
seconds on application start. During this time the
camera screen just stayed black. The whole approach
seems to work a lot better when QMutexes are used.

Task-number: QTBUG-63015
Change-Id: Ib1b0fa1da35fe299896068146254e4cf1d9616fb
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@qt.io>

3 files changed, 15 insertions, 33 deletions

diff --git a/src/plugins/winrt/qwinrtabstractvideorenderercontrol.cpp b/src/plugins/winrt/qwinrtabstractvideorenderercontrol.cpp
index b3fd11111..79545f6ee 100644
--- a/src/plugins/winrt/qwinrtabstractvideorenderercontrol.cpp
+++ b/src/plugins/winrt/qwinrtabstractvideorenderercontrol.cpp
@@ -43,6 +43,7 @@
 #include <QtCore/QGlobalStatic>
 #include <QtCore/QLoggingCategory>
 #include <QtCore/QMetaMethod>
+#include <QtCore/QMutexLocker>
 #include <QtCore/QPointer>
 #include <QtGui/QOpenGLContext>
 #include <QtGui/QOpenGLTexture>
@@ -198,7 +199,7 @@ public:
     QThread renderThread;
     bool active;
     QWinRTAbstractVideoRendererControl::BlitMode blitMode;
-    CRITICAL_SECTION mutex;
+    QMutex mutex;
 };
 
 ID3D11Device *QWinRTAbstractVideoRendererControl::d3dDevice()
@@ -232,7 +233,6 @@ QWinRTAbstractVideoRendererControl::QWinRTAbstractVideoRendererControl(const QSi
     d->eglSurface = EGL_NO_SURFACE;
     d->active = false;
     d->blitMode = DirectVideo;
-    InitializeCriticalSectionEx(&d->mutex, 0, 0);
 
     connect(&d->renderThread, &QThread::started,
             this, &QWinRTAbstractVideoRendererControl::syncAndRender,
@@ -243,9 +243,9 @@ QWinRTAbstractVideoRendererControl::~QWinRTAbstractVideoRendererControl()
 {
     qCDebug(lcMMVideoRender) << __FUNCTION__;
     Q_D(QWinRTAbstractVideoRendererControl);
-    CriticalSectionLocker locker(&d->mutex);
+    QMutexLocker locker(&d->mutex);
     shutdown();
-    DeleteCriticalSection(&d->mutex);
+    locker.unlock();
     eglDestroySurface(d->eglDisplay, d->eglSurface);
 }
 
@@ -272,7 +272,7 @@ void QWinRTAbstractVideoRendererControl::syncAndRender()
         if (currentThread->isInterruptionRequested())
             break;
         {
-            CriticalSectionLocker lock(&d->mutex);
+            QMutexLocker lock(&d->mutex);
             HRESULT hr;
             if (d->dirtyState == TextureDirty) {
                 CD3D11_TEXTURE2D_DESC desc(DXGI_FORMAT_B8G8R8A8_UNORM, d->format.frameWidth(), d->format.frameHeight(), 1, 1);
@@ -359,7 +359,7 @@ void QWinRTAbstractVideoRendererControl::setActive(bool active)
         // This only happens for quick restart scenarios, for instance
         // when switching cameras.
         if (d->renderThread.isRunning() && d->renderThread.isInterruptionRequested()) {
-            CriticalSectionLocker lock(&d->mutex);
+            QMutexLocker lock(&d->mutex);
             d->renderThread.wait();
         }
 
@@ -385,7 +385,7 @@ QWinRTAbstractVideoRendererControl::BlitMode QWinRTAbstractVideoRendererControl:
 void QWinRTAbstractVideoRendererControl::setBlitMode(QWinRTAbstractVideoRendererControl::BlitMode mode)
 {
     Q_D(QWinRTAbstractVideoRendererControl);
-    CriticalSectionLocker lock(&d->mutex);
+    QMutexLocker lock(&d->mutex);
 
     if (d->blitMode == mode)
         return;
diff --git a/src/plugins/winrt/qwinrtabstractvideorenderercontrol.h b/src/plugins/winrt/qwinrtabstractvideorenderercontrol.h
index a7ba2998a..53dcb6b94 100644
--- a/src/plugins/winrt/qwinrtabstractvideorenderercontrol.h
+++ b/src/plugins/winrt/qwinrtabstractvideorenderercontrol.h
@@ -96,22 +96,6 @@ private:
     Q_DECLARE_PRIVATE(QWinRTAbstractVideoRendererControl)
 };
 
-class CriticalSectionLocker
-{
-public:
-    CriticalSectionLocker(CRITICAL_SECTION *section)
-        : m_section(section)
-    {
-        EnterCriticalSection(m_section);
-    }
-    ~CriticalSectionLocker()
-    {
-        LeaveCriticalSection(m_section);
-    }
-private:
-    CRITICAL_SECTION *m_section;
-};
-
 QT_END_NAMESPACE
 
 #endif // QWINRTABSTRACTVIDEORENDERERCONTROL_H
diff --git a/src/plugins/winrt/qwinrtcameracontrol.cpp b/src/plugins/winrt/qwinrtcameracontrol.cpp
index a28d57219..e44f81666 100644
--- a/src/plugins/winrt/qwinrtcameracontrol.cpp
+++ b/src/plugins/winrt/qwinrtcameracontrol.cpp
@@ -47,6 +47,7 @@
 #include "qwinrtcameralockscontrol.h"
 
 #include <QtCore/qfunctions_winrt.h>
+#include <QtCore/QMutex>
 #include <QtCore/QPointer>
 #include <QtGui/QGuiApplication>
 #include <private/qeventdispatcher_winrt_p.h>
@@ -227,8 +228,6 @@ public:
     {
         Q_ASSERT(m_videoRenderer);
 
-        InitializeCriticalSectionEx(&m_mutex, 0, 0);
-
         HRESULT hr;
         hr = MFCreateEventQueue(&m_eventQueue);
         Q_ASSERT_SUCCEEDED(hr);
@@ -238,9 +237,8 @@ public:
 
     ~MediaStream()
     {
-        CriticalSectionLocker locker(&m_mutex);
+        QMutexLocker locker(&m_mutex);
         m_eventQueue->Shutdown();
-        DeleteCriticalSection(&m_mutex);
     }
 
     HRESULT RequestSample()
@@ -254,30 +252,30 @@ public:
 
     HRESULT __stdcall GetEvent(DWORD flags, IMFMediaEvent **event) Q_DECL_OVERRIDE
     {
-        EnterCriticalSection(&m_mutex);
+        QMutexLocker locker(&m_mutex);
         // Create an extra reference to avoid deadlock
         ComPtr<IMFMediaEventQueue> eventQueue = m_eventQueue;
-        LeaveCriticalSection(&m_mutex);
+        locker.unlock();
 
         return eventQueue->GetEvent(flags, event);
     }
 
     HRESULT __stdcall BeginGetEvent(IMFAsyncCallback *callback, IUnknown *state) Q_DECL_OVERRIDE
     {
-        CriticalSectionLocker locker(&m_mutex);
+        QMutexLocker locker(&m_mutex);
         HRESULT hr = m_eventQueue->BeginGetEvent(callback, state);
         return hr;
     }
 
     HRESULT __stdcall EndGetEvent(IMFAsyncResult *result, IMFMediaEvent **event) Q_DECL_OVERRIDE
     {
-        CriticalSectionLocker locker(&m_mutex);
+        QMutexLocker locker(&m_mutex);
         return m_eventQueue->EndGetEvent(result, event);
     }
 
     HRESULT __stdcall QueueEvent(MediaEventType eventType, const GUID &extendedType, HRESULT status, const PROPVARIANT *value) Q_DECL_OVERRIDE
     {
-        CriticalSectionLocker locker(&m_mutex);
+        QMutexLocker locker(&m_mutex);
         return m_eventQueue->QueueEventParamVar(eventType, extendedType, status, value);
     }
 
@@ -372,7 +370,7 @@ public:
     }
 
 private:
-    CRITICAL_SECTION m_mutex;
+    QMutex m_mutex;
     ComPtr<IMFMediaType> m_type;
     IMFMediaSink *m_sink;
     ComPtr<IMFMediaEventQueue> m_eventQueue;