From 65ed4fa2ff95b54eacd82a7fb91f213464796756 Mon Sep 17 00:00:00 2001
From: Mike Krus <mike.krus@kdab.com>
Date: Tue, 10 Dec 2019 09:38:00 +0000
Subject: Use animation rather than event to drive simulation

Using events can be problematic as they contribute to flooding
of the event queue leading to issues with running animations.
So we now use an actual animation which runs in a loop and triggers
every 1ms (rendering still vsync locked though).
If animation have not been enabled for the qt build, we fall back
to using events as before.

Tests were changes since frame progress is no longer driven by
events, so processEvents does not trigger a frame update.

Change-Id: I89b11862ef432dffae0c3dfb140eedd61754697e
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>
---
 src/core/aspects/qaspectmanager.cpp | 48 ++++++++++++++++++++++++++++++++++---
 1 file changed, 45 insertions(+), 3 deletions(-)

(limited to 'src/core/aspects/qaspectmanager.cpp')

diff --git a/src/core/aspects/qaspectmanager.cpp b/src/core/aspects/qaspectmanager.cpp
index f24248399..74803349c 100644
--- a/src/core/aspects/qaspectmanager.cpp
+++ b/src/core/aspects/qaspectmanager.cpp
@@ -65,6 +65,7 @@
 #include <Qt3DCore/private/qscene_p.h>
 
 #include <QtCore/QCoreApplication>
+#include <QtCore/QAbstractAnimation>
 
 #if defined(QT3D_CORE_JOB_TIMING)
 #include <QElapsedTimer>
@@ -74,6 +75,23 @@ QT_BEGIN_NAMESPACE
 
 namespace Qt3DCore {
 
+#if QT_CONFIG(animation)
+class RequestFrameAnimation final : public QAbstractAnimation
+{
+public:
+    RequestFrameAnimation(QObject *parent)
+        : QAbstractAnimation(parent)
+    {
+    }
+
+    ~RequestFrameAnimation() override;
+
+    int duration() const override { return 1; }
+    void updateCurrentTime(int currentTime) override { Q_UNUSED(currentTime) }
+};
+
+RequestFrameAnimation::~RequestFrameAnimation() = default;
+#else
 namespace  {
 
 class RequestFrameEvent : public QEvent
@@ -92,7 +110,7 @@ private:
 int RequestFrameEvent::requestEventType = QEvent::registerEventType();
 
 } // anonymous
-
+#endif
 
 /*!
     \class Qt3DCore::QAspectManager
@@ -108,6 +126,9 @@ QAspectManager::QAspectManager(QObject *parent)
     , m_simulationLoopRunning(false)
     , m_driveMode(QAspectEngine::Automatic)
     , m_postConstructorInit(nullptr)
+#if QT_CONFIG(animation)
+    , m_simulationAnimation(nullptr)
+#endif
 {
     qRegisterMetaType<QSurface *>("QSurface*");
     qCDebug(Aspects) << Q_FUNC_INFO;
@@ -149,8 +170,19 @@ void QAspectManager::enterSimulationLoop()
     qCDebug(Aspects) << "Done calling onEngineStartup() for each aspect";
 
     // Start running loop if Qt3D is in charge of driving it
-    if (m_driveMode == QAspectEngine::Automatic)
+    if (m_driveMode == QAspectEngine::Automatic) {
+#if QT_CONFIG(animation)
+        if (!m_simulationAnimation) {
+            m_simulationAnimation = new RequestFrameAnimation(this);
+            connect(m_simulationAnimation, &QAbstractAnimation::finished, this, [this]() {
+                processFrame();
+                if (m_simulationLoopRunning && m_driveMode == QAspectEngine::Automatic)
+                    requestNextFrame();
+            });
+        }
+#endif
         requestNextFrame();
+    }
 }
 
 // Main thread (called by QAspectEngine)
@@ -164,6 +196,11 @@ void QAspectManager::exitSimulationLoop()
         return;
     }
 
+#if QT_CONFIG(animation)
+    if (m_simulationAnimation)
+        m_simulationAnimation->stop();
+#endif
+
     QAbstractFrameAdvanceService *frameAdvanceService =
             m_serviceLocator->service<QAbstractFrameAdvanceService>(QServiceLocator::FrameAdvanceService);
     if (frameAdvanceService)
@@ -193,7 +230,6 @@ void QAspectManager::exitSimulationLoop()
     }
     qCDebug(Aspects) << "Done calling onEngineShutdown() for each aspect";
 
-
     m_simulationLoopRunning = false;
     qCDebug(Aspects) << "exitSimulationLoop completed";
 }
@@ -399,6 +435,7 @@ QVector<QNode *> QAspectManager::lookupNodes(const QVector<QNodeId> &ids) const
     return d->m_scene ? d->m_scene->lookupNodes(ids) : QVector<QNode *>{};
 }
 
+#if !QT_CONFIG(animation)
 /*!
     \internal
     \brief Drives the Qt3D simulation loop in the main thread
@@ -420,13 +457,18 @@ bool QAspectManager::event(QEvent *e)
 
     return QObject::event(e);
 }
+#endif
 
 void QAspectManager::requestNextFrame()
 {
     qCDebug(Aspects) << "Requesting new Frame";
     // Post event in the event loop to force
     // next frame to be processed
+#if QT_CONFIG(animation)
+    m_simulationAnimation->start();
+#else
     QCoreApplication::postEvent(this, new RequestFrameEvent());
+#endif
 }
 
 void QAspectManager::processFrame()
-- 
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