void FSequencerNodeTree::MakeSectionInterfaces( UMovieSceneTrack& Track, TSharedRef<FTrackNode>& SectionAreaNode )
{
	const TArray<UMovieSceneSection*>& MovieSceneSections = Track.GetAllSections();

	TSharedRef<FMovieSceneTrackEditor> Editor = FindOrAddTypeEditor( Track );

	for (int32 SectionIndex = 0; SectionIndex < MovieSceneSections.Num(); ++SectionIndex )
	{
		UMovieSceneSection* SectionObject = MovieSceneSections[SectionIndex];
		TSharedRef<ISequencerSection> Section = Editor->MakeSectionInterface( *SectionObject, &Track );

		// Ask the section to generate it's inner layout
		FSectionLayoutBuilder Builder( SectionAreaNode );
		Section->GenerateSectionLayout( Builder );

		SectionAreaNode->AddSection( Section );
	}

	SectionAreaNode->FixRowIndices();
}
void FSequencerNodeTree::Update()
{
	// @todo Sequencer - This update pass is too aggressive.  Some nodes may still be valid
	Empty();

	UMovieScene* MovieScene = Sequencer.GetFocusedMovieSceneSequence()->GetMovieScene();

	TArray< TSharedRef<FSequencerDisplayNode> > NewRootNodes;

	// Get the master tracks  so we can get sections from them
	const TArray<UMovieSceneTrack*>& MasterTracks = MovieScene->GetMasterTracks();

	for( UMovieSceneTrack* Track : MasterTracks )
	{
		UMovieSceneTrack& TrackRef = *Track;

		TSharedRef<FTrackNode> SectionNode = MakeShareable( new FTrackNode( TrackRef.GetTrackName(), TrackRef, *FindOrAddTypeEditor(TrackRef), NULL, *this ) );
		NewRootNodes.Add( SectionNode );
	
		MakeSectionInterfaces( TrackRef, SectionNode );
	}


	const TArray<FMovieSceneBinding>& Bindings = MovieScene->GetBindings();

	TMap<FGuid, const FMovieSceneBinding*> GuidToBindingMap;
	for (const FMovieSceneBinding& Binding : Bindings)
	{
		GuidToBindingMap.Add(Binding.GetObjectGuid(), &Binding);
	}

	// Make nodes for all object bindings
	TArray< TSharedRef<FSequencerDisplayNode> > NewObjectNodes;
	for( const FMovieSceneBinding& Binding : Bindings )
	{
		TSharedRef<FObjectBindingNode> ObjectBindingNode = AddObjectBinding( Binding.GetName(), Binding.GetObjectGuid(), GuidToBindingMap, NewObjectNodes );

		const TArray<UMovieSceneTrack*>& Tracks = Binding.GetTracks();

		for( UMovieSceneTrack* Track : Tracks )
		{
			UMovieSceneTrack& TrackRef = *Track;

			FName SectionName = TrackRef.GetTrackName();
			check( SectionName != NAME_None );

			TSharedRef<FTrackNode> SectionAreaNode = ObjectBindingNode->AddSectionAreaNode( SectionName, TrackRef, *FindOrAddTypeEditor( TrackRef ) );
			MakeSectionInterfaces( TrackRef, SectionAreaNode );
		}
	}

	struct FObjectNodeSorter
	{
		bool operator()( const TSharedRef<FSequencerDisplayNode>& A, const TSharedRef<FSequencerDisplayNode>& B ) const
		{
			if (A->GetType() == ESequencerNode::Object && B->GetType() != ESequencerNode::Object)
			{
				return true;
			}
			if (A->GetType() != ESequencerNode::Object && B->GetType() == ESequencerNode::Object)
			{
				return false;
			}
			if ( A->GetType() == ESequencerNode::Object && B->GetType() == ESequencerNode::Object )
			{
				return A->GetDisplayName().ToString() < B->GetDisplayName().ToString();
			}
			return 0;
		}
	};

	NewObjectNodes.Sort( FObjectNodeSorter() );
	for (TSharedRef<FSequencerDisplayNode> NewObjectNode : NewObjectNodes)
	{
		NewObjectNode->SortChildNodes(FObjectNodeSorter());
	}

	NewRootNodes.Append(NewObjectNodes);

	// Look for a shot track.  It will always come first if it exists
	UMovieSceneTrack* ShotTrack = MovieScene->GetShotTrack();
	if( ShotTrack )
	{
		TSharedRef<FTrackNode> SectionNode = MakeShareable( new FTrackNode( ShotTrack->GetTrackName(), *ShotTrack, *FindOrAddTypeEditor( *ShotTrack ), NULL, *this ) );

		// Shot track always comes first
		RootNodes.Add( SectionNode );

		MakeSectionInterfaces( *ShotTrack, SectionNode );
	}

	// Add all other nodes after the shot track
	RootNodes.Append( NewRootNodes );

	// Set up virtual offsets, and expansion states
	float VerticalOffset = 0.f;
	for (auto& Node : RootNodes)
	{
		Node->Traverse_ParentFirst([&](FSequencerDisplayNode& InNode){

			float VerticalTop = VerticalOffset;
			VerticalOffset += InNode.GetNodeHeight() + InNode.GetNodePadding().Combined();
			InNode.Initialize(VerticalTop, VerticalOffset);
			return true;
		});

	}

	// Re-filter the tree after updating 
	// @todo Sequencer - Newly added sections may need to be visible even when there is a filter
	FilterNodes( FilterString );
}