Add stutter tracking

interface/resources/qml/Stats.qml

@@ -69,6 +69,10 @@ Item {
                     StatText {
                         text: "Present Drop Rate: " + root.presentdroprate.toFixed(2);
                     }
+                    StatText {
+                        text: "Stutter Rate: " + root.stutterrate.toFixed(3);
+                        visible: root.stutterrate != -1;
+                    }
                     StatText {
                         text: "Simrate: " + root.simrate
                     }

interface/src/ui/Stats.cpp

@@ -128,7 +128,8 @@ void Stats::updateStats(bool force) {
         STAT_UPDATE(renderrate, displayPlugin->renderRate());
         STAT_UPDATE(presentrate, displayPlugin->presentRate());
         STAT_UPDATE(presentnewrate, displayPlugin->newFramePresentRate());
-        STAT_UPDATE(presentdroprate, qApp->getActiveDisplayPlugin()->droppedFrameRate());
+        STAT_UPDATE(presentdroprate, displayPlugin->droppedFrameRate());
+        STAT_UPDATE(stutterrate, displayPlugin->stutterRate());
     } else {
         STAT_UPDATE(presentrate, -1);
         STAT_UPDATE(presentnewrate, -1);

interface/src/ui/Stats.h

@@ -36,7 +36,9 @@ class Stats : public QQuickItem {
     STATS_PROPERTY(float, renderrate, 0)
     // How often the display plugin is presenting to the device
     STATS_PROPERTY(float, presentrate, 0)
-    
+    // How often the display device reprojecting old frames
+    STATS_PROPERTY(float, stutterrate, 0)
+
     STATS_PROPERTY(float, presentnewrate, 0)
     STATS_PROPERTY(float, presentdroprate, 0)
     STATS_PROPERTY(int, simrate, 0)
@@ -140,6 +142,7 @@ signals:
     void presentrateChanged();
     void presentnewrateChanged();
     void presentdroprateChanged();
+    void stutterrateChanged();
     void simrateChanged();
     void avatarSimrateChanged();
     void avatarCountChanged();

libraries/plugins/src/plugins/DisplayPlugin.h

@@ -188,6 +188,8 @@ public:
     virtual float renderRate() const { return -1.0f; }
     // Rate at which we present to the display device
     virtual float presentRate() const { return -1.0f; }
+    // Rate at which old frames are presented to the device display
+    virtual float stutterRate() const { return -1.0f; }
     // Rate at which new frames are being presented to the display device
     virtual float newFramePresentRate() const { return -1.0f; }
     // Rate at which rendered frames are being skipped

plugins/openvr/src/OpenVrDisplayPlugin.cpp

@@ -641,6 +641,12 @@ void OpenVrDisplayPlugin::hmdPresent() {
         vr::VRCompositor()->PostPresentHandoff();
         _presentRate.increment();
     }
+
+    vr::Compositor_FrameTiming frameTiming;
+    memset(&frameTiming, 0, sizeof(vr::Compositor_FrameTiming));
+    frameTiming.m_nSize = sizeof(vr::Compositor_FrameTiming);
+    vr::VRCompositor()->GetFrameTiming(&frameTiming);
+    _stutterRate.increment(frameTiming.m_nNumDroppedFrames);
 }
 
 void OpenVrDisplayPlugin::postPreview() {
@@ -702,3 +708,7 @@ bool OpenVrDisplayPlugin::isKeyboardVisible() {
 int OpenVrDisplayPlugin::getRequiredThreadCount() const { 
     return Parent::getRequiredThreadCount() + (_threadedSubmit ? 1 : 0);
 }
+
+float OpenVrDisplayPlugin::stutterRate() const {
+    return _stutterRate.rate();
+}

plugins/openvr/src/OpenVrDisplayPlugin.h

@@ -58,6 +58,8 @@ public:
     // Possibly needs an additional thread for VR submission
     int getRequiredThreadCount() const override; 
 
+    float stutterRate() const override;
+
 protected:
     bool internalActivate() override;
     void internalDeactivate() override;
@@ -77,6 +79,7 @@ private:
     vr::HmdMatrix34_t _lastGoodHMDPose;
     mat4 _sensorResetMat;
     bool _threadedSubmit { true };
+    RateCounter<> _stutterRate;
 
     CompositeInfo::Array _compositeInfos;
     size_t _renderingIndex { 0 };