From 806d06b5529104c6f41f1748381204c1f4c6b9fc Mon Sep 17 00:00:00 2001
From: Zach Pomerantz <zach@highfidelity.io>
Date: Thu, 12 May 2016 17:49:47 -0700
Subject: [PATCH] Wait on old entity script engines in threadpool

---
 .../src/EntityTreeRenderer.cpp                | 21 +++++++++++++------
 libraries/script-engine/src/ScriptEngine.h    | 14 ++++++-------
 2 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/libraries/entities-renderer/src/EntityTreeRenderer.cpp b/libraries/entities-renderer/src/EntityTreeRenderer.cpp
index c73a7ae6c7..7643e446ec 100644
--- a/libraries/entities-renderer/src/EntityTreeRenderer.cpp
+++ b/libraries/entities-renderer/src/EntityTreeRenderer.cpp
@@ -13,6 +13,7 @@
 
 #include <QEventLoop>
 #include <QScriptSyntaxCheckResult>
+#include <QThreadPool>
 
 #include <ColorUtils.h>
 #include <AbstractScriptingServicesInterface.h>
@@ -83,14 +84,22 @@ void EntityTreeRenderer::resetEntitiesScriptEngine() {
 
     auto newEngine = new ScriptEngine(NO_SCRIPT, QString("Entities %1").arg(++_entitiesScriptEngineCount));
     _entitiesScriptEngine = QSharedPointer<ScriptEngine>(newEngine, [](ScriptEngine* engine){
-        // Gracefully exit
+        class WaitRunnable : public QRunnable {
+        public:
+            WaitRunnable(ScriptEngine* engine) : _engine(engine) {}
+            virtual void run() override {
+                _engine->wait();
+                _engine->deleteLater();
+            }
+
+        private:
+            ScriptEngine* _engine;
+        };
+
         engine->unloadAllEntityScripts();
         engine->stop();
-
-        // Disgracefully exit, if necessary
-        QTimer::singleShot(ScriptEngine::MAX_SCRIPT_EVALUATION_TIME, engine, &ScriptEngine::abort);
-
-        engine->deleteLater();
+        // Wait for the scripting thread from the thread pool to avoid hanging the main thread
+        QThreadPool::globalInstance()->start(new WaitRunnable(engine));
     });
 
     _scriptingServices->registerScriptEngineWithApplicationServices(_entitiesScriptEngine.data());
diff --git a/libraries/script-engine/src/ScriptEngine.h b/libraries/script-engine/src/ScriptEngine.h
index bb4814eb94..b107e741f4 100644
--- a/libraries/script-engine/src/ScriptEngine.h
+++ b/libraries/script-engine/src/ScriptEngine.h
@@ -83,6 +83,13 @@ public:
     /// run the script in the callers thread, exit when stop() is called.
     void run();
 
+    ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+    // NOTE - this is intended to be a public interface for Agent scripts, and local scripts, but not for EntityScripts
+    Q_INVOKABLE void stop();
+
+    // Stop any evaluating scripts and wait for the scripting thread to finish.
+    void wait();
+
     ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
     // NOTE - these are NOT intended to be public interfaces available to scripts, the are only Q_INVOKABLE so we can
     //        properly ensure they are only called on the correct thread
@@ -138,10 +145,6 @@ public:
 
     Q_INVOKABLE void requestGarbageCollection() { collectGarbage(); }
 
-    ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
-    // NOTE - this is intended to be a public interface for Agent scripts, and local scripts, but not for EntityScripts
-    Q_INVOKABLE void stop();
-
     bool isFinished() const { return _isFinished; } // used by Application and ScriptWidget
     bool isRunning() const { return _isRunning; } // used by ScriptWidget
 
@@ -201,9 +204,6 @@ protected:
     void init();
     QString getFilename() const;
 
-    // Stop any evaluating scripts and wait for the scripting thread to finish.
-    void wait();
-
     bool evaluatePending() const { return _evaluatesPending > 0; }
     void timerFired();
     void stopAllTimers();