recover the Good Parts from first attempt to fix bugz-512

libraries/entities-renderer/src/EntityTreeRenderer.cpp

@@ -256,18 +256,28 @@ void EntityTreeRenderer::clear() {
     }
 
     // reset the engine
-    if (_wantScripts && !_shuttingDown) {
+    auto scene = _viewState->getMain3DScene();
+    if (_shuttingDown) {
+        if (scene) {
+            render::Transaction transaction;
+            for (const auto& entry :  _entitiesInScene) {
+                const auto& renderer = entry.second;
+                renderer->removeFromScene(scene, transaction);
+            }
+            scene->enqueueTransaction(transaction);
+        }
+    } else {
+        if (_wantScripts) {
             resetEntitiesScriptEngine();
         }
-    // remove all entities from the scene
-    auto scene = _viewState->getMain3DScene();
         if (scene) {
             for (const auto& entry :  _entitiesInScene) {
                 const auto& renderer = entry.second;
                 fadeOutRenderable(renderer);
             }
         } else {
-        qCWarning(entitiesrenderer) << "EntitityTreeRenderer::clear(), Unexpected null scene, possibly during application shutdown";
+            qCWarning(entitiesrenderer) << "EntitityTreeRenderer::clear(), Unexpected null scene";
+        }
     }
     _entitiesInScene.clear();
     _renderablesToUpdate.clear();

libraries/entities-renderer/src/RenderableWebEntityItem.cpp

@@ -7,6 +7,7 @@
 //
 
 #include "RenderableWebEntityItem.h"
+#include <atomic>
 
 #include <QtCore/QTimer>
 #include <QtGui/QOpenGLContext>
@@ -46,7 +47,7 @@ static uint64_t MAX_NO_RENDER_INTERVAL = 30 * USECS_PER_SECOND;
 static uint8_t YOUTUBE_MAX_FPS = 30;
 
 // Don't allow more than 20 concurrent web views
-static uint32_t _currentWebCount { 0 };
+static std::atomic<uint32_t> _currentWebCount(0);
 static const uint32_t MAX_CONCURRENT_WEB_VIEWS = 20;
 
 static QTouchDevice _touchDevice;
@@ -356,16 +357,15 @@ void WebEntityRenderer::buildWebSurface(const EntityItemPointer& entity, const Q
 
 void WebEntityRenderer::destroyWebSurface() {
     QSharedPointer<OffscreenQmlSurface> webSurface;
-    ContentType contentType = ContentType::NoContent;
     withWriteLock([&] {
         webSurface.swap(_webSurface);
-        _contentType = contentType;
+        _contentType = ContentType::NoContent;
-    });
 
         if (webSurface) {
             --_currentWebCount;
             WebEntityRenderer::releaseWebSurface(webSurface, _cachedWebSurface, _connections);
         }
+    });
 }
 
 glm::vec2 WebEntityRenderer::getWindowSize(const TypedEntityPointer& entity) const {