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_ViewerOperation.h b/source/blender/compositor/operations/COM_ViewerOperation.h
index 34954382b82..dcc7ffa3730 100644
--- a/source/blender/compositor/operations/COM_ViewerOperation.h
+++ b/source/blender/compositor/operations/COM_ViewerOperation.h
@@ -39,7 +39,7 @@ private:
 	OrderOfChunks m_chunkOrder;
 	bool m_doDepthBuffer;
 	ImBuf *m_ibuf;
-	bool m_ignoreAlpha;
+	bool m_useAlphaInput;
 	
 	const ColorManagedViewSettings *m_viewSettings;
 	const ColorManagedDisplaySettings *m_displaySettings;
@@ -66,7 +66,7 @@ public:
 	OrderOfChunks getChunkOrder() const { return this->m_chunkOrder; }
 	const CompositorPriority getRenderPriority() const;
 	bool isViewerOperation() const { return true; }
-	void setIgnoreAlpha(bool value) { this->m_ignoreAlpha = value; }
+	void setUseAlphaInput(bool value) { this->m_useAlphaInput = value; }
 
 	void setViewSettings(const ColorManagedViewSettings *viewSettings) { this->m_viewSettings = viewSettings; }
 	void setDisplaySettings(const ColorManagedDisplaySettings *displaySettings) { this->m_displaySettings = displaySettings; }