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, 10 insertions, 0 deletions

diff --git a/source/blender/compositor/intern/COM_NodeConverter.cpp b/source/blender/compositor/intern/COM_NodeConverter.cpp
index 5965eade389..81a10a58cc5 100644
--- a/source/blender/compositor/intern/COM_NodeConverter.cpp
+++ b/source/blender/compositor/intern/COM_NodeConverter.cpp
@@ -156,3 +156,13 @@ void NodeConverter::addOutputVector(NodeOutput *output, const float value[3])
 	m_builder->addOperation(operation);
 	m_builder->mapOutputSocket(output, operation->getOutputSocket());
 }
+
+void NodeConverter::registerViewer(ViewerOperation *viewer)
+{
+	m_builder->registerViewer(viewer);
+}
+
+ViewerOperation *NodeConverter::active_viewer() const
+{
+	return m_builder->active_viewer();
+}