Fix: NLA Track Solo flag handling, in depsgraph and F-Curve iteration

This fixes the (unreported) issue where solo'ing an NLA track would only
play back animation when _any_ of the tracks were unmuted.

Some code considered a track to be muted when its `NLATRACK_MUTED` flag
was set regardless of the `NLATRACK_SOLO` flag, whereas other code did
consider the `NLATRACK_SOLO` flag.

Now all the code is consistent with what actual animation evaluation is
doing.

Pull Request: https://projects.blender.org/blender/blender/pulls/134500

source/blender/blenkernel/BKE_nla.hh

@@ -141,6 +141,14 @@ void BKE_nlatrack_remove(ListBase *tracks, NlaTrack *nlt);
  */
 void BKE_nlatrack_remove_and_free(ListBase *tracks, NlaTrack *nlt, bool do_id_user);
 
+/**
+ * Return whether this NLA track is enabled.
+ *
+ * If any track is solo'ed: returns true when this is the solo'ed one.
+ * If no track is solo'ed: returns true when this track is not muted.
+ */
+bool BKE_nlatrack_is_enabled(const AnimData &adt, const NlaTrack &nlt);
+
 /**
  * Compute the length of the passed strip's clip, unless the clip length
  * is zero in which case a non-zero value is returned.

source/blender/blenkernel/intern/anim_data.cc

@@ -1272,7 +1272,7 @@ static void adt_apply_all_fcurves_cb(ID *id,
 
   /* NLA Data - Animation Data for Strips */
   LISTBASE_FOREACH (NlaTrack *, nlt, &adt->nla_tracks) {
-    if (nlt->flag & NLATRACK_MUTED) {
+    if (!BKE_nlatrack_is_enabled(*adt, *nlt)) {
       continue;
     }
     nlastrips_apply_all_curves_cb(id, &nlt->strips, func);

source/blender/blenkernel/intern/anim_sys.cc

@@ -3200,21 +3200,9 @@ static void animsys_evaluate_nla_domain(PointerRNA *ptr, NlaEvalData *channels,
 
   /* NLA Data - Animation Data for Strips */
   LISTBASE_FOREACH (NlaTrack *, nlt, &adt->nla_tracks) {
-    /* solo and muting are mutually exclusive... */
-    if (adt->flag & ADT_NLA_SOLO_TRACK) {
-      /* skip if there is a solo track, but this isn't it */
-      if ((nlt->flag & NLATRACK_SOLO) == 0) {
-        continue;
-      }
-      /* else - mute doesn't matter */
+    if (!BKE_nlatrack_is_enabled(*adt, *nlt)) {
+      continue;
     }
-    else {
-      /* no solo tracks - skip track if muted */
-      if (nlt->flag & NLATRACK_MUTED) {
-        continue;
-      }
-    }
-
     nla_eval_domain_strips(ptr, channels, &nlt->strips, touched_actions);
   }
 
@@ -3325,21 +3313,7 @@ static bool is_nlatrack_evaluatable(const AnimData *adt, const NlaTrack *nlt)
     return false;
   }
 
-  /* Solo and muting are mutually exclusive. */
-  if (adt->flag & ADT_NLA_SOLO_TRACK) {
-    /* Skip if there is a solo track, but this isn't it. */
-    if ((nlt->flag & NLATRACK_SOLO) == 0) {
-      return false;
-    }
-  }
-  else {
-    /* Skip track if muted. */
-    if (nlt->flag & NLATRACK_MUTED) {
-      return false;
-    }
-  }
-
-  return true;
+  return BKE_nlatrack_is_enabled(*adt, *nlt);
 }
 
 /**

source/blender/blenkernel/intern/nla.cc

@@ -667,6 +667,15 @@ void BKE_nlatrack_remove_and_free(ListBase *tracks, NlaTrack *nlt, bool do_id_us
   BKE_nlatrack_free(nlt, do_id_user);
 }
 
+bool BKE_nlatrack_is_enabled(const AnimData &adt, const NlaTrack &nlt)
+{
+  if (adt.flag & ADT_NLA_SOLO_TRACK) {
+    return (nlt.flag & NLATRACK_SOLO);
+  }
+
+  return !(nlt.flag & NLATRACK_MUTED);
+}
+
 /* *************************************************** */
 /* NLA Evaluation <-> Editing Stuff */
 

source/blender/depsgraph/intern/builder/deg_builder_nodes.cc

@@ -77,6 +77,7 @@
 #include "BKE_mesh.hh"
 #include "BKE_modifier.hh"
 #include "BKE_movieclip.h"
+#include "BKE_nla.hh"
 #include "BKE_node.hh"
 #include "BKE_node_runtime.hh"
 #include "BKE_object.hh"
@@ -1253,7 +1254,7 @@ void DepsgraphNodeBuilder::build_animdata(ID *id)
   }
   /* NLA strips contain actions. */
   LISTBASE_FOREACH (NlaTrack *, nlt, &adt->nla_tracks) {
-    if (nlt->flag & NLATRACK_MUTED) {
+    if (!BKE_nlatrack_is_enabled(*adt, *nlt)) {
       continue;
     }
     build_animdata_nlastrip_targets(&nlt->strips);

source/blender/depsgraph/intern/builder/deg_builder_relations.cc

@@ -75,6 +75,7 @@
 #include "BKE_material.hh"
 #include "BKE_mball.hh"
 #include "BKE_modifier.hh"
+#include "BKE_nla.hh"
 #include "BKE_node.hh"
 #include "BKE_node_runtime.hh"
 #include "BKE_object.hh"
@@ -1616,7 +1617,7 @@ void DepsgraphRelationBuilder::build_animdata_curves(ID *id)
     build_animdata_action_targets(id, adt->slot_handle, adt_key, operation_from, adt->action);
   }
   LISTBASE_FOREACH (NlaTrack *, nlt, &adt->nla_tracks) {
-    if (nlt->flag & NLATRACK_MUTED) {
+    if (!BKE_nlatrack_is_enabled(*adt, *nlt)) {
       continue;
     }
     build_animdata_nlastrip_targets(id, adt_key, operation_from, &nlt->strips);