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these functions have been replaced by a non-virtual recursive core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, 22 insertions, 12 deletions

diff --git a/source/blender/compositor/intern/COM_Converter.h b/source/blender/compositor/intern/COM_Converter.h
index 15bda0839fa..c1ad45bbf54 100644
--- a/source/blender/compositor/intern/COM_Converter.h
+++ b/source/blender/compositor/intern/COM_Converter.h
@@ -23,8 +23,13 @@
 #ifndef _COM_Converter_h
 #define _COM_Converter_h
 
-#include "DNA_node_types.h"
-#include "COM_Node.h"
+struct bNode;
+
+class Node;
+class NodeOperation;
+class NodeOperationInput;
+class NodeOperationOutput;
+class NodeOperationBuilder;
 
 /**
  * @brief Conversion methods for the compositor
@@ -35,37 +40,42 @@ public:
 	 * @brief Convert/wraps a bNode in its Node instance.
 	 *
 	 * For all nodetypes a wrapper class is created.
-	 * Muted nodes are wrapped with MuteNode.
 	 *
 	 * @note When adding a new node to blender, this method needs to be changed to return the correct Node instance.
 	 *
 	 * @see Node
-	 * @see MuteNode
 	 */
-	static Node *convert(bNode *b_node, bool fast);
+	static Node *convert(bNode *b_node);
+	
+	/**
+	 * @brief True if the node is considered 'fast'.
+	 *
+	 * Slow nodes will be skipped if fast execution is required.
+	 */
+	static bool is_fast_node(bNode *b_node);
 	
 	/**
 	 * @brief This method will add a datetype conversion rule when the to-socket does not support the from-socket actual data type.
 	 *
 	 * @note this method is called when conversion is needed.
 	 *
-	 * @param connection the SocketConnection what needs conversion
+	 * @param link the NodeLink what needs conversion
 	 * @param system the ExecutionSystem to add the conversion to.
-	 * @see SocketConnection - a link between two sockets
+	 * @see NodeLink - a link between two sockets
 	 */
-	static void convertDataType(SocketConnection *connection, ExecutionSystem *system);
+	static NodeOperation *convertDataType(NodeOperationOutput *from, NodeOperationInput *to);
 	
 	/**
-	 * @brief This method will add a resolution rule based on the settings of the InputSocket.
+	 * @brief This method will add a resolution rule based on the settings of the NodeInput.
 	 *
 	 * @note Conversion logic is implemented in this method
 	 * @see InputSocketResizeMode for the possible conversions.
 	 *
-	 * @param connection the SocketConnection what needs conversion
+	 * @param link the NodeLink what needs conversion
 	 * @param system the ExecutionSystem to add the conversion to.
-	 * @see SocketConnection - a link between two sockets
+	 * @see NodeLink - a link between two sockets
 	 */
-	static void convertResolution(SocketConnection *connection, ExecutionSystem *system);
+	static void convertResolution(NodeOperationBuilder &builder, NodeOperationOutput *fromSocket, NodeOperationInput *toSocket);
 
 #ifdef WITH_CXX_GUARDEDALLOC
 	MEM_CXX_CLASS_ALLOC_FUNCS("COM:Converter")