Toggle links tool for Node Editor

This commit adds a new tool, Toggle Links, to the node editor. This tool
allows the user to toggle the status (linked/not linked) between desired
sockets. The tool can be used either by using the f key or the menus.

This functionality is analogue to one found in object editing modes except
for its additional toggle functionality.

To use this tool, the user has to first select an input and an output socket.
Selecting is done by clicking with right mouse button on a socket. After the 
tool has been invoked, the link between those two sockets is toggled. The 
result may vary based on existing linkage.

There can be only one input and one output selected at maximum in a node 
tree. This means that if the user selects a socket while one of the same 
type is already selected, the old one will be deselected.

The tool complements the current way of connecting nodes. One possible use
for it is to use it to review output of nodes by using a viewer node. Just
select wanted input socket of a viewer node, set it visible and use selection 
of an output socket in conjuction with f key to show the output in the viewer
node. Select another output and hit f to see its output and so on.

1 files changed, 6 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_node_types.h b/source/blender/makesdna/DNA_node_types.h
index 5f20939fc23..b5084c41884 100644
--- a/source/blender/makesdna/DNA_node_types.h
+++ b/source/blender/makesdna/DNA_node_types.h
@@ -92,7 +92,8 @@ typedef struct bNodeSocket {
 #define SOCK_IN_USE				4
 		/* unavailable is for dynamic sockets */
 #define SOCK_UNAVAIL			8
-
+		/* flag for selection status */
+#define SOCK_SEL			16
 #
 #
 typedef struct bNodePreview {
@@ -167,6 +168,10 @@ typedef struct bNodeTree {
 	ListBase alltypes;				/* type definitions */
 	struct bNodeType *owntype;		/* for groups or dynamic trees, no read/write */
 
+	/* selected input/output socket */
+	bNodeSocket *selin;
+	bNodeSocket *selout;
+
 	/* callbacks */
 	void (*timecursor)(int nr);
 	void (*stats_draw)(char *str);