Fix T39799: Backdrop (compositor) ignores alpha.

This issue is because of a somewhat "special" behavior in old code, which got lost during rB09874df:

There was a variant of the `relinkConnections` function which would leave the socket completely unconnected. This is not a valid state really (given that each unconnected input must otherwise connected to a constant `Set` type node), but was used as a way to distinguish connected alpha/depth sockets in composite and viewer output nodes.
https://developer.blender.org/diffusion/B/browse/master/source/blender/compositor/intern/COM_InputSocket.cpp;28a829893c702918afc5ac1945a06eaefa611594$69

After the large cleanup patch ({D309}) every socket is now automatically connected to a constant, such that `getInputSocketReader` will never return a NULL pointer. This breaks the previous test method, which needs to be replaced by more explicit flags. Luckily this was done only for very few output nodes (Composite, Viewer, Output-File). These now use the regular SetValueOperation default in case "use alpha" is disabled, but set this to an explicit 1.0 value instead of mapping to the node socket.

1 files changed, 7 insertions, 0 deletions

diff --git a/source/blender/compositor/intern/COM_NodeConverter.h b/source/blender/compositor/intern/COM_NodeConverter.h
index a67dafde5e1..cad8408a2bf 100644
--- a/source/blender/compositor/intern/COM_NodeConverter.h
+++ b/source/blender/compositor/intern/COM_NodeConverter.h
@@ -75,6 +75,13 @@ public:
 	 */
 	NodeOperationInput *addOutputProxy(NodeOutput *output);
 	
+	/** Define a constant input value. */
+	void addInputValue(NodeOperationInput *input, float value);
+	/** Define a constant input color. */
+	void addInputColor(NodeOperationInput *input, const float value[4]);
+	/** Define a constant input vector. */
+	void addInputVector(NodeOperationInput *input, const float value[3]);
+	
 	/** Define a constant output value. */
 	void addOutputValue(NodeOutput *output, float value);
 	/** Define a constant output color. */