Node callback for handling link insertion and swapping of occupied inputs.

Nodes have a feature for moving existing links to unoccupied sockets when connecting
to an already used input. This is based on the standard legacy socket types (value/float,
vector, color/rgba) and works reasonably well for shader, compositor and texture nodes.

For new pynode systems, however, the hardcoded nature of that feature has major drawbacks:
* It does not take different type systems into account, leading to meaningless connections
  when sockets are swapped and making the feature useless or outright debilitating.
* Advanced socket behaviors would be possible with a registerable callback, e.g. creating
  extensible input lists that move existing connections down to make room for a new link.

Now any handling of new links is done via the 'insert_links' callback, which can also be
registered through the RNA API. For the legacy shader/compo/tex nodes the behavior is the
same, using a C callback.

Note on the 'use_swap' flag: this has been removed because it was meaningless anyway:
It was disabled only for the insert-node-on-link feature, which works only for
completely unconnected nodes anyway, so there would be nothing to swap in the first place.

1 files changed, 1 insertions, 0 deletions

diff --git a/source/blender/nodes/texture/nodes/node_texture_common.c b/source/blender/nodes/texture/nodes/node_texture_common.c
index 914f1ef5110..79a4c4e3a6b 100644
--- a/source/blender/nodes/texture/nodes/node_texture_common.c
+++ b/source/blender/nodes/texture/nodes/node_texture_common.c
@@ -166,6 +166,7 @@ void register_node_type_tex_group(void)
 	ntype.type = NODE_GROUP;
 	ntype.poll = tex_node_poll_default;
 	ntype.poll_instance = node_group_poll_instance;
+	ntype.insert_link = node_insert_link_default;
 	ntype.update_internal_links = node_update_internal_links_default;
 	ntype.ext.srna = RNA_struct_find("TextureNodeGroup");
 	BLI_assert(ntype.ext.srna != NULL);