Depsgraph: First draft of graph filtering API implementation

When this works correctly, we should be able to feed in an existing
depsgraph instance, and get out a "filtered" copy of it that contains
only the subset of nodes needed to evaluate what we're interested in.

The current implementation only filters on ID blocks/nodes,
and starts by building a full new depsgraph instance first.
I'd originally intended to do it per operation instead, copying
over individual nodes as appropriate to have the smallest and least
memory intensive graph possible. However, I ended up running into
into problems with function binding + COW arguments, hence the
current slow solution.

1 files changed, 29 insertions, 0 deletions

diff --git a/source/blender/depsgraph/DEG_depsgraph_query.h b/source/blender/depsgraph/DEG_depsgraph_query.h
index 41650769fcf..b7ecd0544e4 100644
--- a/source/blender/depsgraph/DEG_depsgraph_query.h
+++ b/source/blender/depsgraph/DEG_depsgraph_query.h
@@ -34,6 +34,7 @@
 #define __DEG_DEPSGRAPH_QUERY_H__
 
 #include "DEG_depsgraph.h"
+#include "DEG_depsgraph_build.h"
 
 struct ID;
 
@@ -207,6 +208,34 @@ void DEG_foreach_dependent_ID(const Depsgraph *depsgraph,
 void DEG_foreach_ID(const Depsgraph *depsgraph,
                     DEGForeachIDCallback callback, void *user_data);
 
+/* ********************* DEG graph filtering ****************** */
+
+/* ComponentKey for nodes we want to be able to evaluate in the filtered graph */
+typedef struct DEG_FilterTarget {
+	struct DEG_FilterTarget *next, *prev;
+
+	struct ID *id;
+	/* TODO: component identifiers - Component Type, Subdata/Component Name */
+} DEG_FilterTarget;
+
+typedef enum eDEG_FilterQuery_Granularity {
+	DEG_FILTER_NODES_ALL           = 0,
+	DEG_FILTER_NODES_NO_OPS        = 1,
+	DEG_FILTER_NODES_ID_ONLY       = 2,
+} eDEG_FilterQuery_Granularity;
+
+
+typedef struct DEG_FilterQuery {
+	/* List of DEG_FilterTarget's */
+	struct ListBase targets;
+
+	/* Level of detail in the resulting graph */
+	eDEG_FilterQuery_Granularity detail_level;
+} DEG_FilterQuery;
+
+/* Obtain a new graph instance that only contains the subset of desired nodes */
+Depsgraph *DEG_graph_filter(const Depsgraph *depsgraph, struct Main *bmain, DEG_FilterQuery *query);
+
 
 #ifdef __cplusplus
 } /* extern "C" */