Depsgraph: New dependency graph integration commit

This commit integrates the work done so far on the new dependency graph system,
where goal was to replace legacy depsgraph with the new one, supporting loads of
neat features like:

- More granular dependency relation nature, which solves issues with fake cycles
  in the dependencies.

- Move towards all-animatable, by better integration of drivers into the system.

- Lay down some basis for upcoming copy-on-write, overrides and so on.

The new system is living side-by-side with the previous one and disabled by
default, so nothing will become suddenly broken. The way to enable new depsgraph
is to pass `--new-depsgraph` command line argument.

It's a bit early to consider the system production-ready, there are some TODOs
and issues were discovered during the merge period, they'll be addressed ASAP.
But it's important to merge, because it's the only way to attract artists to
really start testing this system.

There are number of assorted documents related on the design of the new system:

* http://wiki.blender.org/index.php/User:Aligorith/GSoC2013_Depsgraph#Design_Documents
* http://wiki.blender.org/index.php/User:Nazg-gul/DependencyGraph

There are also some user-related information online:

* http://code.blender.org/2015/02/blender-dependency-graph-branch-for-users/
* http://code.blender.org/2015/03/more-dependency-graph-tricks/

Kudos to everyone who was involved into the project:

- Joshua "Aligorith" Leung -- design specification, initial code
- Lukas "lukas_t" Toenne -- integrating code into blender, with further fixes
- Sergey "Sergey" "Sharybin" -- some mocking around, trying to wrap up the
  project and so
- Bassam "slikdigit" Kurdali -- stressing the new system, reporting all the
  issues and recording/writing documentation.
- Everyone else who i forgot to mention here :)

1 files changed, 87 insertions, 0 deletions

diff --git a/source/blender/depsgraph/intern/depsgraph_queue.h b/source/blender/depsgraph/intern/depsgraph_queue.h
new file mode 100644
index 00000000000..bd294d4655e
--- /dev/null
+++ b/source/blender/depsgraph/intern/depsgraph_queue.h
@@ -0,0 +1,87 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2013 Blender Foundation.
+ * All rights reserved.
+ *
+ * Original Author: Joshua Leung
+ * Contributor(s): None Yet
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ *
+ * Defines for special queue type for use in Depsgraph traversals
+ */
+
+#ifndef __DEPSGRAPH_QUEUE_H__
+#define __DEPSGRAPH_QUEUE_H__
+
+struct DepsNode;
+
+struct Heap;
+struct GHash;
+
+/* *********************************************** */
+/* Dependency Graph Traversal Queue
+ *
+ * There are two parts to this:
+ * a) "Pending" Nodes - This part contains the set of nodes
+ *    which are related to those which have been visited
+ *    previously, but are not yet ready to actually be visited.
+ * b) "Scheduled" Nodes - These are the nodes whose ancestors
+ *    have all been evaluated already, which means that any
+ *    or all of them can be picked (in practically in order) to
+ *    be visited immediately.
+ *
+ * Internally, the queue makes sure that each node in the graph
+ * only gets added to the queue once. This is because there can
+ * be multiple inlinks to each node given the way that the relations
+ * work.
+ */
+
+/* Depsgraph Queue Type */
+typedef struct DepsgraphQueue {
+	/* Pending */
+	struct Heap *pending_heap;         /* (valence:int, DepsNode*) */
+	struct GHash *pending_hash;        /* (DepsNode* : HeapNode*>) */
+
+	/* Ready to be visited - fifo */
+	struct Heap *ready_heap;           /* (idx:int, DepsNode*) */
+
+	/* Size/Order counts */
+	size_t idx;                        /* total number of nodes which are/have been ready so far (including those already visited) */
+	size_t tot;                        /* total number of nodes which have passed through queue; mainly for debug */
+} DepsgraphQueue;
+
+/* ************************** */
+/* Depsgraph Queue Operations */
+
+/* Data management */
+DepsgraphQueue *DEG_queue_new(void);
+void DEG_queue_free(DepsgraphQueue *q);
+
+/* Statistics */
+size_t DEG_queue_num_pending(DepsgraphQueue *q);
+size_t DEG_queue_num_ready(DepsgraphQueue *q);
+
+size_t DEG_queue_size(DepsgraphQueue *q);
+bool DEG_queue_is_empty(DepsgraphQueue *q);
+
+/* Operations */
+void DEG_queue_push(DepsgraphQueue *q, void *dnode, float cost = 0.0f);
+void *DEG_queue_pop(DepsgraphQueue *q);
+
+#endif  /* DEPSGRAPH_QUEUE_H */