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, 6 insertions, 3 deletions

diff --git a/source/blender/compositor/operations/COM_OutputFileOperation.h b/source/blender/compositor/operations/COM_OutputFileOperation.h
index 6bb2e7d7320..03278c5b149 100644
--- a/source/blender/compositor/operations/COM_OutputFileOperation.h
+++ b/source/blender/compositor/operations/COM_OutputFileOperation.h
@@ -62,11 +62,14 @@ public:
 
 /* extra info for OpenEXR layers */
 struct OutputOpenExrLayer {
-	OutputOpenExrLayer(const char *name, DataType datatype);
+	OutputOpenExrLayer(const char *name, DataType datatype, bool use_layer);
 	
 	char name[EXR_TOT_MAXNAME - 2];
-	float *outputBuffer;
 	DataType datatype;
+	bool use_layer;
+	
+	/* internals */
+	float *outputBuffer;
 	SocketReader *imageInput;
 };
 
@@ -85,7 +88,7 @@ private:
 public:
 	OutputOpenExrMultiLayerOperation(const RenderData *rd, const bNodeTree *tree, const char *path, char exr_codec);
 	
-	void add_layer(const char *name, DataType datatype);
+	void add_layer(const char *name, DataType datatype, bool use_layer);
 	
 	void executeRegion(rcti *rect, unsigned int tileNumber);
 	bool isOutputOperation(bool rendering) const { return true; }