Clean up the async loading fix a bit

Reduce unnecessary mutex locking in synchronous case.

Task-number: QT3DS-3226
Change-Id: I8990b7809a2e5914a7ec80d7500a8f5247870f86
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>
Reviewed-by: Tomi Korpipää <tomi.korpipaa@qt.io>

2 files changed, 32 insertions, 10 deletions

diff --git a/src/runtime/q3dsengine.cpp b/src/runtime/q3dsengine.cpp
index ef72f00..2e568b0 100644
--- a/src/runtime/q3dsengine.cpp
+++ b/src/runtime/q3dsengine.cpp
@@ -107,6 +107,12 @@ static QStringList q3ds_msg_buf;
 static QtMessageHandler q3ds_prev_msg_handler = nullptr;
 static Q3DSEngine *q3ds_msg_engine = nullptr;
 
+static bool isAsyncLoadingEnabled()
+{
+    static bool enabled = (qEnvironmentVariableIntValue("Q3DS_ASYNC_LOADING")) > 0;
+    return enabled;
+}
+
 void Q3DSEngine::clearLog()
 {
     QMutexLocker locker(&q3ds_msg_mutex);
@@ -172,6 +178,11 @@ Q3DSEngine::Q3DSEngine()
     initResources();
     registerQmlTypes();
 
+    if (isAsyncLoadingEnabled()) {
+        m_slideResourceMutex = new QMutex;
+        m_asyncLoadMutex = new QMutex;
+    }
+
     QMutexLocker locker(&q3ds_msg_mutex);
     q3ds_msg_engine = this;
     // Install the message handler once, it is then set for ever. Engines come
@@ -903,15 +914,18 @@ void Q3DSEngine::beginAsyncLoad(Q3DSSubPresentation &sp, SceneLoaderAsync *loade
         qCDebug(lcScene, "Subpresentation %s loaded in %lld ms",
                 qPrintable(loader->pres->subPres.id), timer.elapsed());
     });
-    QMutexLocker locker(&m_asyncLoadLock);
+    QMutexLocker locker(m_asyncLoadMutex);
     m_asyncSceneLoaders.push_back(loader);
 }
 
 void Q3DSEngine::finishAsyncLoadForSubpresentation(const QString &name)
 {
+    if (!m_asyncLoadMutex)
+        return;
+
     QVector<SceneLoaderAsync *> loaders;
     {
-        QMutexLocker locker(&m_asyncLoadLock);
+        QMutexLocker locker(m_asyncLoadMutex);
         loaders = m_asyncSceneLoaders;
     }
     for (auto &item : qAsConst(loaders)) {
@@ -926,10 +940,13 @@ void Q3DSEngine::finishAsyncLoadForSubpresentation(const QString &name)
 
 void Q3DSEngine::finishAsyncLoad(bool wait)
 {
+    if (!m_asyncLoadMutex)
+        return;
+
     QThread *currentThread = QThread::currentThread();
     QVector<SceneLoaderAsync *> loaders;
     {
-        QMutexLocker locker(&m_asyncLoadLock);
+        QMutexLocker locker(m_asyncLoadMutex);
         loaders = m_asyncSceneLoaders;
     }
     if (wait) {
@@ -962,13 +979,18 @@ void Q3DSEngine::finishAsyncLoad(bool wait)
 
 void Q3DSEngine::loadSlideResources(Q3DSSlide *slide, Q3DSUipPresentation *presentation)
 {
-    QSet<QUrl> createSet;
-    {
-        QMutexLocker locker(&m_slideResourceMutex);
+    if (m_slideResourceMutex) {
+        QSet<QUrl> createSet;
+        {
+            QMutexLocker locker(m_slideResourceMutex);
+            m_resourceReferenceCounter.handleLoadSlide(slide, presentation);
+            createSet = m_resourceReferenceCounter.createSet;
+        }
+        Q3DSImageManager::instance().beginImageLoad(createSet);
+    } else {
         m_resourceReferenceCounter.handleLoadSlide(slide, presentation);
-        createSet = m_resourceReferenceCounter.createSet;
+        Q3DSImageManager::instance().beginImageLoad(m_resourceReferenceCounter.createSet);
     }
-    Q3DSImageManager::instance().beginImageLoad(createSet);
 }
 
 void Q3DSEngine::unloadSlideResources(Q3DSSlide *slide, Q3DSUipPresentation *presentation)
diff --git a/src/runtime/q3dsengine_p.h b/src/runtime/q3dsengine_p.h
index ae76bb4..1d3f23d 100644
--- a/src/runtime/q3dsengine_p.h
+++ b/src/runtime/q3dsengine_p.h
@@ -472,8 +472,8 @@ private:
 
     QVector<SceneLoaderAsync *> m_asyncSceneLoaders;
     SlideResourceCounter m_resourceReferenceCounter;
-    QMutex m_slideResourceMutex;
-    QMutex m_asyncLoadLock;
+    QMutex *m_slideResourceMutex = nullptr;
+    QMutex *m_asyncLoadMutex= nullptr;
 };
 
 Q_DECLARE_OPERATORS_FOR_FLAGS(Q3DSEngine::Flags)