LibOverride: Add initial support for adding new NLA tracks.

Also makes NLA tracks and strips overridable.

User can either edit existing strips in existing NLA tracks (but not add or remove them), and/or add new NLA tracks after those comming from the linked data.

Most of the work was as usual checking operators and adding protections against illegal operations in override context.

Note that since we can only rely on indices to deal with local added tracks, we forbid any local track being before any linked/original track.

Maniphest Tasks: T72629

Differential Revision: https://developer.blender.org/D9611

1 files changed, 47 insertions, 5 deletions

diff --git a/source/blender/editors/animation/anim_channels_edit.c b/source/blender/editors/animation/anim_channels_edit.c
index ba3796ad245..124992bed71 100644
--- a/source/blender/editors/animation/anim_channels_edit.c
+++ b/source/blender/editors/animation/anim_channels_edit.c
@@ -49,6 +49,7 @@
 #include "BKE_gpencil.h"
 #include "BKE_lib_id.h"
 #include "BKE_mask.h"
+#include "BKE_nla.h"
 #include "BKE_scene.h"
 
 #include "DEG_depsgraph.h"
@@ -1063,18 +1064,27 @@ static void rearrange_animchannels_filter_visible(ListBase *anim_data_visible,
                                                   eAnim_ChannelType type)
 {
   ListBase anim_data = {NULL, NULL};
-  bAnimListElem *ale, *ale_next;
-  int filter = (ANIMFILTER_DATA_VISIBLE | ANIMFILTER_LIST_VISIBLE | ANIMFILTER_LIST_CHANNELS);
+  eAnimFilter_Flags filter = (ANIMFILTER_DATA_VISIBLE | ANIMFILTER_LIST_VISIBLE |
+                              ANIMFILTER_LIST_CHANNELS);
 
   /* get all visible channels */
   ANIM_animdata_filter(ac, &anim_data, filter, ac->data, ac->datatype);
 
   /* now, only keep the ones that are of the types we are interested in */
-  for (ale = anim_data.first; ale; ale = ale_next) {
-    ale_next = ale->next;
-
+  LISTBASE_FOREACH_MUTABLE (bAnimListElem *, ale, &anim_data) {
     if (ale->type != type) {
       BLI_freelinkN(&anim_data, ale);
+      continue;
+    }
+
+    if (type == ANIMTYPE_NLATRACK) {
+      NlaTrack *nlt = (NlaTrack *)ale->data;
+
+      if (BKE_nlatrack_is_nonlocal_in_liboverride(ale->id, nlt)) {
+        /* No re-arrangement of non-local tracks of override data. */
+        BLI_freelinkN(&anim_data, ale);
+        continue;
+      }
     }
   }
 
@@ -1146,6 +1156,7 @@ static void rearrange_nla_channels(bAnimContext *ac, AnimData *adt, eRearrangeAn
 {
   AnimChanRearrangeFp rearrange_func;
   ListBase anim_data_visible = {NULL, NULL};
+  const bool is_liboverride = ID_IS_OVERRIDE_LIBRARY(ac->obact);
 
   /* hack: invert mode so that functions will work in right order */
   mode *= -1;
@@ -1156,6 +1167,29 @@ static void rearrange_nla_channels(bAnimContext *ac, AnimData *adt, eRearrangeAn
     return;
   }
 
+  /* In liboverride case, we need to extract non-local NLA tracks from current anim data before we
+   * can perform the move, and add then back afterwards. It's the only way to prevent them from
+   * being affected by the reordering.
+   *
+   * Note that both override apply code for NLA tracks collection, and NLA editing code, are
+   * responsible to ensure that non-local tracks always remain first in the list. */
+  ListBase extracted_nonlocal_nla_tracks = {NULL, NULL};
+  if (is_liboverride) {
+    NlaTrack *nla_track;
+    for (nla_track = adt->nla_tracks.first; nla_track != NULL; nla_track = nla_track->next) {
+      if (!BKE_nlatrack_is_nonlocal_in_liboverride(&ac->obact->id, nla_track)) {
+        break;
+      }
+    }
+    if (nla_track != NULL && nla_track->prev != NULL) {
+      extracted_nonlocal_nla_tracks.first = adt->nla_tracks.first;
+      extracted_nonlocal_nla_tracks.last = nla_track->prev;
+      adt->nla_tracks.first = nla_track;
+      nla_track->prev->next = NULL;
+      nla_track->prev = NULL;
+    }
+  }
+
   /* Filter visible data. */
   rearrange_animchannels_filter_visible(&anim_data_visible, ac, ANIMTYPE_NLATRACK);
 
@@ -1163,6 +1197,14 @@ static void rearrange_nla_channels(bAnimContext *ac, AnimData *adt, eRearrangeAn
   rearrange_animchannel_islands(
       &adt->nla_tracks, rearrange_func, mode, ANIMTYPE_NLATRACK, &anim_data_visible);
 
+  /* Add back non-local NLA tracks at the begining of the animation data's list. */
+  if (!BLI_listbase_is_empty(&extracted_nonlocal_nla_tracks)) {
+    BLI_assert(is_liboverride);
+    ((NlaTrack *)extracted_nonlocal_nla_tracks.last)->next = adt->nla_tracks.first;
+    ((NlaTrack *)adt->nla_tracks.first)->prev = extracted_nonlocal_nla_tracks.last;
+    adt->nla_tracks.first = extracted_nonlocal_nla_tracks.first;
+  }
+
   /* free temp data */
   BLI_freelistN(&anim_data_visible);
 }