T77086 Animation: Passing Dependency Graph to Drivers

Custom driver functions need access to the dependency graph that is
triggering the evaluation of the driver. This patch passes the
dependency graph pointer through all the animation-related calls.

Instead of passing the evaluation time to functions, the code now passes
an `AnimationEvalContext` pointer:

```
typedef struct AnimationEvalContext {
  struct Depsgraph *const depsgraph;
  const float eval_time;
} AnimationEvalContext;
```

These structs are read-only, meaning that the code cannot change the
evaluation time. Note that the `depsgraph` pointer itself is const, but
it points to a non-const depsgraph.

FCurves and Drivers can be evaluated at a different time than the
current scene time, for example when evaluating NLA strips. This means
that, even though the current time is stored in the dependency graph, we
need an explicit evaluation time.

There are two functions that allow creation of `AnimationEvalContext`
objects:

- `BKE_animsys_eval_context_construct(Depsgraph *depsgraph, float
  eval_time)`, which creates a new context object from scratch, and
- `BKE_animsys_eval_context_construct_at(AnimationEvalContext
  *anim_eval_context, float eval_time)`, which can be used to create a
  `AnimationEvalContext` with the same depsgraph, but at a different
  time. This makes it possible to later add fields without changing any
  of the code that just want to change the eval time.

This also provides a fix for T75553, although it does require a change
to the custom driver function. The driver should call
`custom_function(depsgraph)`, and the function should use that depsgraph
instead of information from `bpy.context`.

Reviewed By: brecht, sergey

Differential Revision: https://developer.blender.org/D8047

2 files changed, 15 insertions, 5 deletions

diff --git a/source/blender/editors/armature/pose_lib.c b/source/blender/editors/armature/pose_lib.c
index 6ce9ed06f1a..c9d0478270a 100644
--- a/source/blender/editors/armature/pose_lib.c
+++ b/source/blender/editors/armature/pose_lib.c
@@ -1023,7 +1023,8 @@ static void poselib_backup_free_data(tPoseLib_PreviewData *pld)
  * - gets the string to print in the header
  * - this code is based on the code for extract_pose_from_action in blenkernel/action.c
  */
-static void poselib_apply_pose(tPoseLib_PreviewData *pld)
+static void poselib_apply_pose(tPoseLib_PreviewData *pld,
+                               const AnimationEvalContext *anim_eval_context)
 {
   PointerRNA *ptr = &pld->rna_ptr;
   bArmature *arm = pld->arm;
@@ -1049,6 +1050,8 @@ static void poselib_apply_pose(tPoseLib_PreviewData *pld)
   group_ok_cb = ANIM_editkeyframes_ok(BEZT_OK_FRAMERANGE);
   ked.f1 = ((float)frame) - 0.5f;
   ked.f2 = ((float)frame) + 0.5f;
+  AnimationEvalContext anim_context_at_frame = BKE_animsys_eval_context_construct_at(
+      anim_eval_context, frame);
 
   /* start applying - only those channels which have a key at this point in time! */
   for (agrp = act->groups.first; agrp; agrp = agrp->next) {
@@ -1075,7 +1078,7 @@ static void poselib_apply_pose(tPoseLib_PreviewData *pld)
         }
 
         if (ok) {
-          animsys_evaluate_action_group(ptr, act, agrp, (float)frame);
+          animsys_evaluate_action_group(ptr, act, agrp, &anim_context_at_frame);
         }
       }
     }
@@ -1150,7 +1153,11 @@ static void poselib_preview_apply(bContext *C, wmOperator *op)
     /* pose should be the right one to draw (unless we're temporarily not showing it) */
     if ((pld->flag & PL_PREVIEW_SHOWORIGINAL) == 0) {
       RNA_int_set(op->ptr, "pose_index", BLI_findindex(&pld->act->markers, pld->marker));
-      poselib_apply_pose(pld);
+      struct Depsgraph *depsgraph = CTX_data_depsgraph_pointer(C);
+
+      const AnimationEvalContext anim_eval_context = BKE_animsys_eval_context_construct(
+          depsgraph, 0.0f /* poselib_apply_pose() determines its own evaluation time. */);
+      poselib_apply_pose(pld, &anim_eval_context);
     }
     else {
       RNA_int_set(op->ptr, "pose_index", -2); /* -2 means don't apply any pose */
diff --git a/source/blender/editors/armature/pose_transform.c b/source/blender/editors/armature/pose_transform.c
index 1d2bf152777..615d59c3154 100644
--- a/source/blender/editors/armature/pose_transform.c
+++ b/source/blender/editors/armature/pose_transform.c
@@ -1219,7 +1219,9 @@ static int pose_clear_user_transforms_exec(bContext *C, wmOperator *op)
   ViewLayer *view_layer = CTX_data_view_layer(C);
   View3D *v3d = CTX_wm_view3d(C);
   Scene *scene = CTX_data_scene(C);
-  float cframe = (float)CFRA;
+  Depsgraph *depsgraph = CTX_data_depsgraph_pointer(C);
+  const AnimationEvalContext anim_eval_context = BKE_animsys_eval_context_construct(depsgraph,
+                                                                                    (float)CFRA);
   const bool only_select = RNA_boolean_get(op->ptr, "only_selected");
 
   FOREACH_OBJECT_IN_MODE_BEGIN (view_layer, v3d, OB_ARMATURE, OB_MODE_POSE, ob) {
@@ -1240,7 +1242,8 @@ static int pose_clear_user_transforms_exec(bContext *C, wmOperator *op)
       workob.adt = ob->adt;
       workob.pose = dummyPose;
 
-      BKE_animsys_evaluate_animdata(&workob.id, workob.adt, cframe, ADT_RECALC_ANIM, false);
+      BKE_animsys_evaluate_animdata(
+          &workob.id, workob.adt, &anim_eval_context, ADT_RECALC_ANIM, false);
 
       /* copy back values, but on selected bones only  */
       for (pchan = dummyPose->chanbase.first; pchan; pchan = pchan->next) {