Avoid node tree update tag when changed nodes which are not affecting result

This was we don't have re-compo or viewport re-rendering happening when changing
nodes which are not connected to the output at all (for example when adding new
nodes or changing settings for unconnected nodes).

Only basic operations are covered for now. checks could be added to more tools
when needed.

Currently it's not fully optimal implementation, but seems to work fast enough.
Don't see reliable alternative to that -- keeping tag in the node wouldn't work
because of the node groups (which are probably already broken, but should be
easy to solve with current approach). So guess it's more matter of optimizing
path search from a node to output.

Before processing forward let's check whether it's indeed something we want
and whether the approach is indeed not fully bad.

Reviewers: campbellbarton, mont29

Subscribers: sebastian_k

Differential Revision: https://developer.blender.org/D1765

1 files changed, 98 insertions, 8 deletions

diff --git a/source/blender/editors/space_node/node_relationships.c b/source/blender/editors/space_node/node_relationships.c
index 0852b6164d3..50d7df6ee20 100644
--- a/source/blender/editors/space_node/node_relationships.c
+++ b/source/blender/editors/space_node/node_relationships.c
@@ -59,6 +59,55 @@
 
 #include "node_intern.h"  /* own include */
 
+/* ****************** Relations helpers *********************** */
+
+static bool ntree_check_nodes_connected_dfs(bNodeTree *ntree,
+                                            bNode *from,
+                                            bNode *to)
+{
+	if (from->flag & NODE_TEST) {
+		return false;
+	}
+	from->flag |= NODE_TEST;
+	for (bNodeLink *link = ntree->links.first; link != NULL; link = link->next) {
+		if (link->fromnode == from) {
+			if (link->tonode == to) {
+				return true;
+			}
+			else {
+				if (ntree_check_nodes_connected_dfs(ntree, link->tonode, to)) {
+					return true;
+				}
+			}
+		}
+	}
+	return false;
+}
+
+static bool ntree_check_nodes_connected(bNodeTree *ntree, bNode *from, bNode *to)
+{
+	if (from == to) {
+		return true;
+	}
+	ntreeNodeFlagSet(ntree, NODE_TEST, false);
+	return ntree_check_nodes_connected_dfs(ntree, from, to);
+}
+
+bool node_connected_to_output(bNodeTree *ntree, bNode *node)
+{
+	for (bNode *current_node = ntree->nodes.first;
+	     current_node != NULL;
+	     current_node = current_node->next)
+	{
+		if (current_node->flag & NODE_DO_OUTPUT) {
+			if (ntree_check_nodes_connected(ntree, node, current_node)) {
+				return true;
+			}
+		}
+	}
+	return false;
+}
+
 /* ****************** Add *********************** */
 
 
@@ -468,7 +517,8 @@ static void node_link_exit(bContext *C, wmOperator *op, bool apply_links)
 	bNodeTree *ntree = snode->edittree;
 	bNodeLinkDrag *nldrag = op->customdata;
 	LinkData *linkdata;
-	
+	bool do_tag_update = false;
+
 	/* avoid updates while applying links */
 	ntree->is_updating = true;
 	for (linkdata = nldrag->links.first; linkdata; linkdata = linkdata->next) {
@@ -493,15 +543,27 @@ static void node_link_exit(bContext *C, wmOperator *op, bool apply_links)
 			
 			/* we might need to remove a link */
 			node_remove_extra_links(snode, link);
+
+			if (link->tonode) {
+				do_tag_update |= (do_tag_update || node_connected_to_output(ntree, link->tonode));
+			}
 		}
-		else
+		else {
+			/* See note below, but basically TEST flag means that the link
+			 * was connected to output (or to a node which affects the
+			 * output).
+			 */
+			do_tag_update |= (link->flag & NODE_LINK_TEST) != 0;
 			nodeRemLink(ntree, link);
+		}
 	}
 	ntree->is_updating = false;
 	
 	ntreeUpdateTree(CTX_data_main(C), ntree);
 	snode_notify(C, snode);
-	snode_dag_update(C, snode);
+	if (do_tag_update) {
+		snode_dag_update(C, snode);
+	}
 	
 	BLI_remlink(&snode->linkdrag, nldrag);
 	/* links->data pointers are either held by the tree or freed already */
@@ -632,7 +694,18 @@ static bNodeLinkDrag *node_link_init(SpaceNode *snode, float cursor[2], bool det
 					*oplink = *link;
 					oplink->next = oplink->prev = NULL;
 					oplink->flag |= NODE_LINK_VALID;
-					
+
+					/* The link could be disconnected and in that case we
+					 * wouldn't be able to check whether tag update is
+					 * needed or not when releasing mouse button. So we
+					 * cache whether the link affects output or not here
+					 * using TEST flag.
+					 */
+					oplink->flag &= ~NODE_LINK_TEST;
+					if (node_connected_to_output(snode->edittree, link->tonode)) {
+						oplink->flag |= NODE_LINK_TEST;
+					}
+
 					BLI_addtail(&nldrag->links, linkdata);
 					nodeRemLink(snode->edittree, link);
 				}
@@ -647,7 +720,11 @@ static bNodeLinkDrag *node_link_init(SpaceNode *snode, float cursor[2], bool det
 			oplink->fromnode = node;
 			oplink->fromsock = sock;
 			oplink->flag |= NODE_LINK_VALID;
-			
+			oplink->flag &= ~NODE_LINK_TEST;
+			if (node_connected_to_output(snode->edittree, node)) {
+				oplink->flag |= NODE_LINK_TEST;
+			}
+
 			BLI_addtail(&nldrag->links, linkdata);
 		}
 	}
@@ -668,7 +745,11 @@ static bNodeLinkDrag *node_link_init(SpaceNode *snode, float cursor[2], bool det
 					*oplink = *link;
 					oplink->next = oplink->prev = NULL;
 					oplink->flag |= NODE_LINK_VALID;
-					
+					oplink->flag &= ~NODE_LINK_TEST;
+					if (node_connected_to_output(snode->edittree, link->tonode)) {
+						oplink->flag |= NODE_LINK_TEST;
+					}
+
 					BLI_addtail(&nldrag->links, linkdata);
 					nodeRemLink(snode->edittree, link);
 					
@@ -687,7 +768,11 @@ static bNodeLinkDrag *node_link_init(SpaceNode *snode, float cursor[2], bool det
 			oplink->tonode = node;
 			oplink->tosock = sock;
 			oplink->flag |= NODE_LINK_VALID;
-			
+			oplink->flag &= ~NODE_LINK_TEST;
+			if (node_connected_to_output(snode->edittree, node)) {
+				oplink->flag |= NODE_LINK_TEST;
+			}
+
 			BLI_addtail(&nldrag->links, linkdata);
 		}
 	}
@@ -817,6 +902,7 @@ static int cut_links_exec(bContext *C, wmOperator *op)
 	ARegion *ar = CTX_wm_region(C);
 	float mcoords[256][2];
 	int i = 0;
+	bool do_tag_update = false;
 
 	RNA_BEGIN (op->ptr, itemptr, "path")
 	{
@@ -849,6 +935,8 @@ static int cut_links_exec(bContext *C, wmOperator *op)
 					found = true;
 				}
 
+				do_tag_update |= (do_tag_update || node_connected_to_output(snode->edittree, link->tonode));
+
 				snode_update(snode, link->tonode);
 				nodeRemLink(snode->edittree, link);
 			}
@@ -857,7 +945,9 @@ static int cut_links_exec(bContext *C, wmOperator *op)
 		if (found) {
 			ntreeUpdateTree(CTX_data_main(C), snode->edittree);
 			snode_notify(C, snode);
-			snode_dag_update(C, snode);
+			if (do_tag_update) {
+				snode_dag_update(C, snode);
+			}
 
 			return OPERATOR_FINISHED;
 		}