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, 37 insertions, 15 deletions

diff --git a/source/blender/blenkernel/intern/nla.c b/source/blender/blenkernel/intern/nla.c
index 56bd83140bf..ebd9317fcf1 100644
--- a/source/blender/blenkernel/intern/nla.c
+++ b/source/blender/blenkernel/intern/nla.c
@@ -280,7 +280,7 @@ void BKE_nla_tracks_copy(Main *bmain, ListBase *dst, ListBase *src, const int fl
 /* Add a NLA Track to the given AnimData
  * - prev: NLA-Track to add the new one after
  */
-NlaTrack *BKE_nlatrack_add(AnimData *adt, NlaTrack *prev)
+NlaTrack *BKE_nlatrack_add(AnimData *adt, NlaTrack *prev, const bool is_liboverride)
 {
   NlaTrack *nlt;
 
@@ -293,11 +293,15 @@ NlaTrack *BKE_nlatrack_add(AnimData *adt, NlaTrack *prev)
   nlt = MEM_callocN(sizeof(NlaTrack), "NlaTrack");
 
   /* set settings requiring the track to not be part of the stack yet */
-  nlt->flag = NLATRACK_SELECTED;
+  nlt->flag = NLATRACK_SELECTED | NLATRACK_OVERRIDELIBRARY_LOCAL;
   nlt->index = BLI_listbase_count(&adt->nla_tracks);
 
   /* add track to stack, and make it the active one */
-  if (prev) {
+  if (is_liboverride) {
+    for (; prev != NULL && (prev->flag & NLATRACK_OVERRIDELIBRARY_LOCAL) == 0; prev = prev->next) {
+    }
+  }
+  if (prev != NULL) {
     BLI_insertlinkafter(&adt->nla_tracks, prev, nlt);
   }
   else {
@@ -359,7 +363,7 @@ NlaStrip *BKE_nlastrip_new(bAction *act)
 
 /* Add new NLA-strip to the top of the NLA stack - i.e.
  * into the last track if space, or a new one otherwise. */
-NlaStrip *BKE_nlastack_add_strip(AnimData *adt, bAction *act)
+NlaStrip *BKE_nlastack_add_strip(AnimData *adt, bAction *act, const bool is_liboverride)
 {
   NlaStrip *strip;
   NlaTrack *nlt;
@@ -376,12 +380,12 @@ NlaStrip *BKE_nlastack_add_strip(AnimData *adt, bAction *act)
   }
 
   /* firstly try adding strip to last track, but if that fails, add to a new track */
-  if (BKE_nlatrack_add_strip(adt->nla_tracks.last, strip) == 0) {
+  if (BKE_nlatrack_add_strip(adt->nla_tracks.last, strip, is_liboverride) == 0) {
     /* trying to add to the last track failed (no track or no space),
      * so add a new track to the stack, and add to that...
      */
-    nlt = BKE_nlatrack_add(adt, NULL);
-    BKE_nlatrack_add_strip(nlt, strip);
+    nlt = BKE_nlatrack_add(adt, NULL, is_liboverride);
+    BKE_nlatrack_add_strip(nlt, strip, is_liboverride);
   }
 
   /* automatically name it too */
@@ -1138,15 +1142,16 @@ void BKE_nlatrack_sort_strips(NlaTrack *nlt)
 /* Add the given NLA-Strip to the given NLA-Track, assuming that it
  * isn't currently attached to another one
  */
-bool BKE_nlatrack_add_strip(NlaTrack *nlt, NlaStrip *strip)
+bool BKE_nlatrack_add_strip(NlaTrack *nlt, NlaStrip *strip, const bool is_liboverride)
 {
   /* sanity checks */
   if (ELEM(NULL, nlt, strip)) {
     return false;
   }
 
-  /* do not allow adding strips if this track is locked */
-  if (nlt->flag & NLATRACK_PROTECTED) {
+  /* Do not allow adding strips if this track is locked, or not a local one in liboverride case. */
+  if (nlt->flag & NLATRACK_PROTECTED ||
+      (is_liboverride && (nlt->flag & NLATRACK_OVERRIDELIBRARY_LOCAL) == 0)) {
     return false;
   }
 
@@ -1186,6 +1191,18 @@ bool BKE_nlatrack_get_bounds(NlaTrack *nlt, float bounds[2])
   return true;
 }
 
+/**
+ * Check whether given NLA track is not local (i.e. from linked data) when the object is a library
+ * override.
+ *
+ * \param nlt May be NULL, in which case we consider it as a non-local track case.
+ */
+bool BKE_nlatrack_is_nonlocal_in_liboverride(const ID *id, const NlaTrack *nlt)
+{
+  return (ID_IS_OVERRIDE_LIBRARY(id) &&
+          (nlt == NULL || (nlt->flag & NLATRACK_OVERRIDELIBRARY_LOCAL) == 0));
+}
+
 /* NLA Strips -------------------------------------- */
 
 /* Find the active NLA-strip within the given track */
@@ -1857,7 +1874,7 @@ bool BKE_nla_action_is_stashed(AnimData *adt, bAction *act)
 /* "Stash" an action (i.e. store it as a track/layer in the NLA, but non-contributing)
  * to retain it in the file for future uses
  */
-bool BKE_nla_action_stash(AnimData *adt)
+bool BKE_nla_action_stash(AnimData *adt, const bool is_liboverride)
 {
   NlaTrack *prev_track = NULL;
   NlaTrack *nlt;
@@ -1881,7 +1898,7 @@ bool BKE_nla_action_stash(AnimData *adt)
     }
   }
 
-  nlt = BKE_nlatrack_add(adt, prev_track);
+  nlt = BKE_nlatrack_add(adt, prev_track, is_liboverride);
   BLI_assert(nlt != NULL);
 
   /* We need to ensure that if there wasn't any previous instance,
@@ -1901,7 +1918,7 @@ bool BKE_nla_action_stash(AnimData *adt)
   strip = BKE_nlastrip_new(adt->action);
   BLI_assert(strip != NULL);
 
-  BKE_nlatrack_add_strip(nlt, strip);
+  BKE_nlatrack_add_strip(nlt, strip, is_liboverride);
   BKE_nlastrip_validate_name(adt, strip);
 
   /* mark the stash track and strip so that they doesn't disturb the stack animation,
@@ -1931,7 +1948,7 @@ bool BKE_nla_action_stash(AnimData *adt)
  * so no checks for this are performed.
  */
 /* TODO: maybe we should have checks for this too... */
-void BKE_nla_action_pushdown(AnimData *adt)
+void BKE_nla_action_pushdown(AnimData *adt, const bool is_liboverride)
 {
   NlaStrip *strip;
   const bool is_first = (adt) && (adt->nla_tracks.first == NULL);
@@ -1952,7 +1969,7 @@ void BKE_nla_action_pushdown(AnimData *adt)
   }
 
   /* add a new NLA strip to the track, which references the active action */
-  strip = BKE_nlastack_add_strip(adt, adt->action);
+  strip = BKE_nlastack_add_strip(adt, adt->action, is_liboverride);
   if (strip == NULL) {
     return;
   }
@@ -2273,6 +2290,11 @@ void BKE_nla_blend_read_lib(BlendLibReader *reader, ID *id, ListBase *tracks)
 {
   /* we only care about the NLA strips inside the tracks */
   LISTBASE_FOREACH (NlaTrack *, nlt, tracks) {
+    /* If linking from a library, clear 'local' library override flag. */
+    if (id->lib != NULL) {
+      nlt->flag &= ~NLATRACK_OVERRIDELIBRARY_LOCAL;
+    }
+
     blend_lib_read_nla_strips(reader, id, &nlt->strips);
   }
 }