Fix test failure, add comments

nyalldawson · nyalldawson · commit 80159c2c36c7 · 2018-07-16T11:38:13.000+10:00
diff --git a/src/gui/processing/qgsprocessingtoolboxmodel.cpp b/src/gui/processing/qgsprocessingtoolboxmodel.cpp
@@ -75,19 +75,15 @@ void QgsProcessingToolboxModelNode::deleteChildren()
 //
 
 QgsProcessingToolboxModelProviderNode::QgsProcessingToolboxModelProviderNode( QgsProcessingProvider *provider )
-  : mProvider( provider )
+  : mProviderId( provider->id() )
+  , mProvider( provider )
 {}
 
 QgsProcessingProvider *QgsProcessingToolboxModelProviderNode::provider()
 {
   return mProvider;
 }
 
-QString QgsProcessingToolboxModelProviderNode::providerId() const
-{
-  return mProvider ? mProvider->id() : QString();
-}
-
 //
 // QgsProcessingToolboxModelGroupNode
 //
diff --git a/src/gui/processing/qgsprocessingtoolboxmodel.h b/src/gui/processing/qgsprocessingtoolboxmodel.h
@@ -175,11 +175,17 @@ class GUI_EXPORT QgsProcessingToolboxModelProviderNode : public QgsProcessingToo
     /**
      * Returns the provider ID.
      */
-    QString providerId() const;
+    QString providerId() const { return mProviderId; }
 
   private:
 
-    QgsProcessingProvider *mProvider = nullptr;
+    // NOTE: we store both the provider ID and a pointer to the provider here intentionally.
+    // We store the provider pointer to avoid having to lookup the provider from the registry
+    // everytime the node is used (which kills performance in the filter proxy model), but
+    // we also store the provider id string in order to identify the provider that the node
+    // is linked to for cleanups after the provider is removed.
+    QString mProviderId;
+    QPointer< QgsProcessingProvider > mProvider;
 
 };
 
