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, 12 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_modifier.h b/source/blender/blenkernel/BKE_modifier.h
index 9c5261c1583..cc53f9409fd 100644
--- a/source/blender/blenkernel/BKE_modifier.h
+++ b/source/blender/blenkernel/BKE_modifier.h
@@ -43,6 +43,7 @@ struct bArmature;
 struct Main;
 struct ModifierData;
 struct BMEditMesh;
+struct DepsNodeHandle;
 
 typedef enum {
 	/* Should not be used, only for None modifier type */
@@ -260,6 +261,17 @@ typedef struct ModifierTypeInfo {
 	                       struct Main *bmain, struct Scene *scene,
 	                       struct Object *ob, struct DagNode *obNode);
 
+	/* Add the appropriate relations to the dependency graph.
+	 *
+	 * This function is optional.
+	 */
+	/* TODO(sergey): Remove once we finalyl switched to the new depsgraph. */
+	void (*updateDepsgraph)(struct ModifierData *md,
+	                        struct Main *bmain,
+	                        struct Scene *scene,
+	                        struct Object *ob,
+	                        struct DepsNodeHandle *node);
+
 	/* Should return true if the modifier needs to be recalculated on time
 	 * changes.
 	 *