Fix T40986: crash on using the viewer node inside of group nodes.

Viewers were activated both inside the active group as well as the top
level tree (the latter being a quick fix for getting a fallback viewer).
This caused a race condition on the shared viewer image.

Now the active viewer is defined at node conversion time in the converter
so that only one can be active at a time without each node having to
follow complicated rules for exclusion.

1 files changed, 22 insertions, 1 deletions

diff --git a/source/blender/compositor/intern/COM_NodeOperationBuilder.cpp b/source/blender/compositor/intern/COM_NodeOperationBuilder.cpp
index a90bac847c0..6554926991c 100644
--- a/source/blender/compositor/intern/COM_NodeOperationBuilder.cpp
+++ b/source/blender/compositor/intern/COM_NodeOperationBuilder.cpp
@@ -38,12 +38,14 @@ extern "C" {
 #include "COM_SocketProxyOperation.h"
 #include "COM_ReadBufferOperation.h"
 #include "COM_WriteBufferOperation.h"
+#include "COM_ViewerOperation.h"
 
 #include "COM_NodeOperationBuilder.h" /* own include */
 
 NodeOperationBuilder::NodeOperationBuilder(const CompositorContext *context, bNodeTree *b_nodetree) :
     m_context(context),
-    m_current_node(NULL)
+    m_current_node(NULL),
+    m_active_viewer(NULL)
 {
 	m_graph.from_bNodeTree(*context, b_nodetree);
 }
@@ -239,6 +241,25 @@ void NodeOperationBuilder::addNodeInputPreview(NodeInput *input)
 	}
 }
 
+void NodeOperationBuilder::registerViewer(ViewerOperation *viewer)
+{
+	if (m_active_viewer) {
+		if (m_current_node->isInActiveGroup()) {
+			/* deactivate previous viewer */
+			m_active_viewer->setActive(false);
+			
+			m_active_viewer = viewer;
+			viewer->setActive(true);
+		}
+	}
+	else {
+		if (m_current_node->getbNodeTree() == m_context->getbNodeTree()) {
+			m_active_viewer = viewer;
+			viewer->setActive(true);
+		}
+	}
+}
+
 /****************************
  **** Optimization Steps ****
  ****************************/