From dd6a4dd091b87262716db6ece18dc8a8dd77f665 Mon Sep 17 00:00:00 2001
From: Zach Pomerantz <zach@highfidelity.io>
Date: Tue, 10 May 2016 16:06:33 -0700
Subject: [PATCH] Make getPaintDelayUsecs threadsafe

---
 libraries/plugins/src/plugins/DisplayPlugin.cpp | 6 +++++-
 libraries/plugins/src/plugins/DisplayPlugin.h   | 3 ++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/libraries/plugins/src/plugins/DisplayPlugin.cpp b/libraries/plugins/src/plugins/DisplayPlugin.cpp
index f52910b952..430da00061 100644
--- a/libraries/plugins/src/plugins/DisplayPlugin.cpp
+++ b/libraries/plugins/src/plugins/DisplayPlugin.cpp
@@ -25,13 +25,17 @@ void DisplayPlugin::deactivate() {
 }
 
 int64_t DisplayPlugin::getPaintDelayUsecs() const {
+    std::lock_guard<std::mutex> lock(_paintDelayMutex);
     return _paintDelayTimer.isValid() ? _paintDelayTimer.nsecsElapsed() / NSECS_PER_USEC : 0;
 }
 
 void DisplayPlugin::incrementPresentCount() {
 #ifdef DEBUG_PAINT_DELAY
     // Avoid overhead if we are not debugging
-    _paintDelayTimer.start();
+    {
+        std::lock_guard<std::mutex> lock(_paintDelayMutex);
+        _paintDelayTimer.start();
+    }
 #endif
 
     ++_presentedFrameIndex;
diff --git a/libraries/plugins/src/plugins/DisplayPlugin.h b/libraries/plugins/src/plugins/DisplayPlugin.h
index 1e9b16eeac..3a668f27d7 100644
--- a/libraries/plugins/src/plugins/DisplayPlugin.h
+++ b/libraries/plugins/src/plugins/DisplayPlugin.h
@@ -161,7 +161,7 @@ public:
     // Rate at which rendered frames are being skipped
     virtual float droppedFrameRate() const { return -1.0f; }
     uint32_t presentCount() const { return _presentedFrameIndex; }
-    // Time since last call to incrementPresentCount. Only valid if DEBUG_PAINT_DELAY is defined
+    // Time since last call to incrementPresentCount (only valid if DEBUG_PAINT_DELAY is defined)
     int64_t getPaintDelayUsecs() const;
 
     virtual void cycleDebugOutput() {}
@@ -176,6 +176,7 @@ protected:
 
 private:
     std::atomic<uint32_t> _presentedFrameIndex;
+    mutable std::mutex _paintDelayMutex;
     QElapsedTimer _paintDelayTimer;
 };