Structural cleanup and improvements for the compositor.

Many parts of the compositor are unnecessarily complicated. This patch
aims at reducing the complexity of writing nodes and making the code
more transparent.

== Separating Nodes and Operations ==

Currently these are both mixed in the same graph, even though they have
very different purposes and are used at distinct stages in the
compositing process. The patch introduces dedicated graph classes for
nodes and for operations.

This removes the need for a lot of special case checks (isOperation etc.)
and explicit type casts. It simplifies the code since it becomes clear
at every stage what type of node we are dealing with. The compiler can
use static typing to avoid common bugs from mixing up these types and
fewer runtime sanity checks are needed.

== Simplified Node Conversion ==

Converting nodes to operations was previously based on "relinking", i.e.
nodes would start with by mirroring links in the Blender DNA node trees,
then add operations and redirect these links to them. This was very hard
to follow in many cases and required a lot of attention to avoid invalid
states.

Now there is a helper class called the NodeConverter, which is passed to
nodes and implements a much simpler API for this process. Nodes can add
operations and explicit connections as before, but defining "external"
links to the inputs/outputs of the original node now uses mapping
instead of directly modifying link data. Input data (node graph) and
result (operations graph) are cleanly separated.

== Removed Redundant Data Structures ==

A few redundant data structures have been removed, notably the
SocketConnection. These are only needed temporarily during graph
construction. For executing the compositor operations it is perfectly
sufficient to store only the direct input link pointers. A common
pointer indirection is avoided this way (which might also give a little
performance improvement).

== Avoid virtual recursive functions ==

Recursive virtual functions are evil. They are very hard to follow
during debugging. At least in the parts this patch is concerned with
these functions have been replaced by a non-virtual recursive core
function (which might then call virtual non-recursive functions if
needed). See for example NodeOperationBuilder::group_operations.

1 files changed, 103 insertions, 0 deletions

diff --git a/source/blender/compositor/intern/COM_NodeConverter.h b/source/blender/compositor/intern/COM_NodeConverter.h
new file mode 100644
index 00000000000..51a1a44cade
--- /dev/null
+++ b/source/blender/compositor/intern/COM_NodeConverter.h
@@ -0,0 +1,103 @@
+/*
+ * Copyright 2013, Blender Foundation.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * Contributor: 
+ *		Lukas Toenne
+ */
+
+#ifndef _COM_NodeCompiler_h
+#define _COM_NodeCompiler_h
+
+class NodeInput;
+class NodeOutput;
+
+class NodeOperation;
+class NodeOperationInput;
+class NodeOperationOutput;
+class NodeOperationBuilder;
+
+/** Interface type for converting a \a Node into \a NodeOperation.
+ *  This is passed to \a Node::convertToOperation methods and allows them
+ *  to register any number of operations, create links between them,
+ *  and map original node sockets to their inputs or outputs.
+ */
+class NodeConverter {
+public:
+	NodeConverter(NodeOperationBuilder *builder);
+	
+	/** Insert a new operation into the operations graph.
+	 *  The operation must be created by the node.
+	 */
+	void addOperation(NodeOperation *operation);
+	
+	/** Map input socket of the node to an operation socket.
+	 *  Links between nodes will then generate equivalent links between
+	 *  the mapped operation sockets.
+	 * 
+	 *  \note A \a Node input can be mapped to multiple \a NodeOperation inputs.
+	 */
+	void mapInputSocket(NodeInput *node_socket, NodeOperationInput *operation_socket);
+	/** Map output socket of the node to an operation socket.
+	 *  Links between nodes will then generate equivalent links between
+	 *  the mapped operation sockets.
+	 * 
+	 * \note A \a Node output can only be mapped to one \a NodeOperation output.
+	 * Any existing operation output mapping will be replaced.
+	 */
+	void mapOutputSocket(NodeOutput *node_socket, NodeOperationOutput *operation_socket);
+	
+	/** Create a proxy operation for a node input.
+	 *  This operation will be removed later and replaced
+	 *  by direct links between the connected operations.
+	 */
+	NodeOperationOutput *addInputProxy(NodeInput *input);
+	/** Create a proxy operation for a node output.
+	 *  This operation will be removed later and replaced
+	 *  by direct links between the connected operations.
+	 */
+	NodeOperationInput *addOutputProxy(NodeOutput *output);
+	
+	/** Define a constant output value. */
+	void addOutputValue(NodeOutput *output, float value);
+	/** Define a constant output color. */
+	void addOutputColor(NodeOutput *output, const float value[4]);
+	/** Define a constant output vector. */
+	void addOutputVector(NodeOutput *output, const float value[3]);
+	
+	/** Add an explicit link between two operations. */
+	void addLink(NodeOperationOutput *from, NodeOperationInput *to);
+	
+	/** Add a preview operation for a operation output. */
+	void addPreview(NodeOperationOutput *output);
+	/** Add a preview operation for a node input. */
+	void addNodeInputPreview(NodeInput *input);
+	
+	/** When a node has no valid data
+	 *  @note missing image / group pointer, or missing renderlayer from EXR
+	 */
+	NodeOperation *setInvalidOutput(NodeOutput *output);
+	
+private:
+	/** The internal builder for storing the results of the graph construction. */
+	NodeOperationBuilder *m_builder;
+
+#ifdef WITH_CXX_GUARDEDALLOC
+	MEM_CXX_CLASS_ALLOC_FUNCS("COM:NodeCompiler")
+#endif
+};
+
+#endif /* _COM_NodeCompiler_h */