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, 2 insertions, 2 deletions

diff --git a/source/blender/compositor/operations/COM_CompositorOperation.h b/source/blender/compositor/operations/COM_CompositorOperation.h
index d33e89ed742..771c32ffd12 100644
--- a/source/blender/compositor/operations/COM_CompositorOperation.h
+++ b/source/blender/compositor/operations/COM_CompositorOperation.h
@@ -69,7 +69,7 @@ private:
 	/**
 	 * @brief Ignore any alpha input
 	 */
-	bool m_ignoreAlpha;
+	bool m_useAlphaInput;
 
 	/**
 	 * @brief operation is active for calculating final compo result
@@ -86,7 +86,7 @@ public:
 	void deinitExecution();
 	const CompositorPriority getRenderPriority() const { return COM_PRIORITY_MEDIUM; }
 	void determineResolution(unsigned int resolution[2], unsigned int preferredResolution[2]);
-	void setIgnoreAlpha(bool value) { this->m_ignoreAlpha = value; }
+	void setUseAlphaInput(bool value) { this->m_useAlphaInput = value; }
 	void setActive(bool active) { this->m_active = active; }
 };
 #endif