From a40a562db21152bd94a393b2226d5586b8606c04 Mon Sep 17 00:00:00 2001
From: Brad Hefta-Gaub <brad@highfidelity.io>
Date: Thu, 11 Feb 2016 09:30:06 -0800
Subject: [PATCH] handle two conner cases where preload would get called twice

---
 .../src/EntityTreeRenderer.cpp                |  3 ++-
 libraries/entities/src/EntityItem.h           | 20 +++++++++++++++++++
 libraries/entities/src/EntityTree.cpp         |  3 +++
 libraries/entities/src/EntityTreeElement.cpp  |  8 +++++++-
 4 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/libraries/entities-renderer/src/EntityTreeRenderer.cpp b/libraries/entities-renderer/src/EntityTreeRenderer.cpp
index 0ea35e6c5a..1967e14d6e 100644
--- a/libraries/entities-renderer/src/EntityTreeRenderer.cpp
+++ b/libraries/entities-renderer/src/EntityTreeRenderer.cpp
@@ -690,10 +690,11 @@ void EntityTreeRenderer::entitySciptChanging(const EntityItemID& entityID, const
 void EntityTreeRenderer::checkAndCallPreload(const EntityItemID& entityID, const bool reload) {
     if (_tree && !_shuttingDown) {
         EntityItemPointer entity = getTree()->findEntityByEntityItemID(entityID);
-        if (entity && !entity->getScript().isEmpty()) {
+        if (entity && entity->shouldPreloadScript()) {
             QString scriptUrl = entity->getScript();
             scriptUrl = ResourceManager::normalizeURL(scriptUrl);
             _entitiesScriptEngine->loadEntityScript(entityID, scriptUrl, reload);
+            entity->scriptHasPreloaded();
         }
     }
 }
diff --git a/libraries/entities/src/EntityItem.h b/libraries/entities/src/EntityItem.h
index 55741823f1..da10886b97 100644
--- a/libraries/entities/src/EntityItem.h
+++ b/libraries/entities/src/EntityItem.h
@@ -404,6 +404,20 @@ public:
 
     virtual void loader() {} // called indirectly when urls for geometry are updated
 
+    /// Has the entity been added to an entity tree? This is useful in some state decisions
+    /// for example whether or not to send out a scriptChanging signal.
+    void markAsAddedToTree() { _isAddedToTree = true; }
+    bool isAddedToTree() const { return _isAddedToTree; }
+
+    /// Should the external entity script mechanism call a preload for this entity.
+    /// Due to the asyncronous nature of signals for add entity and script changing
+    /// it's possible for two similar signals to cross paths. This method allows the
+    /// entity to definitively state if the preload signal should be sent.
+    bool shouldPreloadScript() const { return !_script.isEmpty() &&  
+                                _loadedScript != _script && _loadedScriptTimestamp != _scriptTimestamp; }
+
+    void scriptHasPreloaded() { _loadedScript = _script; _loadedScriptTimestamp = _scriptTimestamp; }
+
 protected:
 
     void setSimulated(bool simulated) { _simulated = simulated; }
@@ -506,6 +520,12 @@ protected:
     mutable QHash<QUuid, quint64> _previouslyDeletedActions;
 
     QUuid _sourceUUID; /// the server node UUID we came from
+
+    bool _isAddedToTree { false }; /// this is false until the entity has been added to an entity tree
+
+    QString _loadedScript; /// the value of _script when the last preload signal was sent
+    quint64 _loadedScriptTimestamp { 0 };  /// the value of _scriptTimestamp when the last preload signal was sent
+
 };
 
 #endif // hifi_EntityItem_h
diff --git a/libraries/entities/src/EntityTree.cpp b/libraries/entities/src/EntityTree.cpp
index 4c3412edd3..fc463b6f21 100644
--- a/libraries/entities/src/EntityTree.cpp
+++ b/libraries/entities/src/EntityTree.cpp
@@ -92,6 +92,9 @@ void EntityTree::postAddEntity(EntityItemPointer entity) {
 
     // find and hook up any entities with this entity as a (previously) missing parent
     fixupMissingParents();
+
+    // indicate that the entity has been added to the tree
+    entity->markAsAddedToTree();
 }
 
 bool EntityTree::updateEntity(const EntityItemID& entityID, const EntityItemProperties& properties, const SharedNodePointer& senderNode) {
diff --git a/libraries/entities/src/EntityTreeElement.cpp b/libraries/entities/src/EntityTreeElement.cpp
index 1e798f2e0c..d58faa81fe 100644
--- a/libraries/entities/src/EntityTreeElement.cpp
+++ b/libraries/entities/src/EntityTreeElement.cpp
@@ -921,7 +921,13 @@ int EntityTreeElement::readElementDataFromBuffer(const unsigned char* data, int
                     QString entityScriptAfter = entityItem->getScript();
                     quint64 entityScriptTimestampAfter = entityItem->getScriptTimestamp();
                     bool reload = entityScriptTimestampBefore != entityScriptTimestampAfter;
-                    if (entityScriptBefore != entityScriptAfter || reload) {
+
+                    // If the script value has changed on us, or it's timestamp has changed to force
+                    // a reload then we want to send out a script changing signal... UNLESS this is the
+                    // first time we've read the entity information, in which case, the entity has
+                    // not yet been added to the tree, and we want to wait for the addEntity. In other
+                    // words it's not a "change" in the script, if it's a first time load.
+                    if (entityItem->isAddedToTree() && (entityScriptBefore != entityScriptAfter || reload)) {
                         _myTree->emitEntityScriptChanging(entityItemID, reload); // the entity script has changed
                     }