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these functions have been replaced by a non-virtual recursive core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, 17 insertions, 14 deletions

diff --git a/source/blender/compositor/intern/COM_Debug.h b/source/blender/compositor/intern/COM_Debug.h
index cc108157769..204e7e4f57c 100644
--- a/source/blender/compositor/intern/COM_Debug.h
+++ b/source/blender/compositor/intern/COM_Debug.h
@@ -27,7 +27,6 @@
 
 #include "COM_defines.h"
 
-class NodeBase;
 class Node;
 class NodeOperation;
 class ExecutionSystem;
@@ -41,37 +40,41 @@ public:
 		EG_FINISHED
 	} GroupState;
 	
-	typedef std::map<NodeBase *, std::string> NodeNameMap;
-	typedef std::map<ExecutionGroup *, GroupState> GroupStateMap;
+	typedef std::map<const Node *, std::string> NodeNameMap;
+	typedef std::map<const NodeOperation *, std::string> OpNameMap;
+	typedef std::map<const ExecutionGroup *, GroupState> GroupStateMap;
 	
-	static std::string node_name(NodeBase *node);
+	static std::string node_name(const Node *node);
+	static std::string operation_name(const NodeOperation *op);
 	
 	static void convert_started();
-	static void execute_started(ExecutionSystem *system);
+	static void execute_started(const ExecutionSystem *system);
 	
-	static void node_added(Node *node);
-	static void node_to_operations(Node *node);
-	static void operation_added(NodeOperation *operation);
-	static void operation_read_write_buffer(NodeOperation *operation);
+	static void node_added(const Node *node);
+	static void node_to_operations(const Node *node);
+	static void operation_added(const NodeOperation *operation);
+	static void operation_read_write_buffer(const NodeOperation *operation);
 	
-	static void execution_group_started(ExecutionGroup *group);
-	static void execution_group_finished(ExecutionGroup *group);
+	static void execution_group_started(const ExecutionGroup *group);
+	static void execution_group_finished(const ExecutionGroup *group);
 	
-	static void graphviz(ExecutionSystem *system);
+	static void graphviz(const ExecutionSystem *system);
 	
 #ifdef COM_DEBUG
 protected:
-	static int graphviz_operation(ExecutionSystem *system, NodeOperation *operation, ExecutionGroup *group, char *str, int maxlen);
+	static int graphviz_operation(const ExecutionSystem *system, const NodeOperation *operation, const ExecutionGroup *group, char *str, int maxlen);
 	static int graphviz_legend_color(const char *name, const char *color, char *str, int maxlen);
 	static int graphviz_legend_line(const char *name, const char *color, const char *style, char *str, int maxlen);
 	static int graphviz_legend_group(const char *name, const char *color, const char *style, char *str, int maxlen);
 	static int graphviz_legend(char *str, int maxlen);
-	static bool graphviz_system(ExecutionSystem *system, char *str, int maxlen);
+	static bool graphviz_system(const ExecutionSystem *system, char *str, int maxlen);
 	
 private:
 	static int m_file_index;
 	static NodeNameMap m_node_names;			/**< map nodes to usable names for debug output */
+	static OpNameMap m_op_names;				/**< map operations to usable names for debug output */
 	static std::string m_current_node_name;		/**< base name for all operations added by a node */
+	static std::string m_current_op_name;		/**< base name for automatic sub-operations */
 	static GroupStateMap m_group_states;		/**< for visualizing group states */
 #endif
 };