VSE: Add API function to select displayed meta strip

Use function `sequence_editor.display_stack(meta_strip)` to set
displayed timeline content.

To view top-level timeline, that does not belong to any meta strip, pass
`None` as argument.

Differential Revision: https://developer.blender.org/D12048

3 files changed, 60 insertions, 25 deletions

diff --git a/source/blender/sequencer/intern/sequencer.c b/source/blender/sequencer/intern/sequencer.c
index ad57412034a..71f4aef6916 100644
--- a/source/blender/sequencer/intern/sequencer.c
+++ b/source/blender/sequencer/intern/sequencer.c
@@ -397,23 +397,23 @@ void SEQ_seqbase_active_set(Editing *ed, ListBase *seqbase)
   ed->seqbasep = seqbase;
 }
 
-MetaStack *SEQ_meta_stack_alloc(Editing *ed, Sequence *seq_meta)
+static MetaStack *seq_meta_stack_alloc(const Scene *scene, Sequence *seq_meta)
 {
+  Editing *ed = SEQ_editing_get(scene);
+
   MetaStack *ms = MEM_mallocN(sizeof(MetaStack), "metastack");
-  BLI_addtail(&ed->metastack, ms);
+  BLI_addhead(&ed->metastack, ms);
   ms->parseq = seq_meta;
-  ms->oldbasep = ed->seqbasep;
-  ms->old_channels = ed->displayed_channels;
+
+  /* Reference to previously displayed timeline data. */
+  Sequence *higher_level_meta = seq_sequence_lookup_meta_by_seq(scene, seq_meta);
+  ms->oldbasep = higher_level_meta ? &higher_level_meta->seqbase : &ed->seqbase;
+  ms->old_channels = higher_level_meta ? &higher_level_meta->channels : &ed->channels;
+
   copy_v2_v2_int(ms->disp_range, &ms->parseq->startdisp);
   return ms;
 }
 
-void SEQ_meta_stack_free(Editing *ed, MetaStack *ms)
-{
-  BLI_remlink(&ed->metastack, ms);
-  MEM_freeN(ms);
-}
-
 MetaStack *SEQ_meta_stack_active_get(const Editing *ed)
 {
   if (ed == NULL) {
@@ -423,6 +423,41 @@ MetaStack *SEQ_meta_stack_active_get(const Editing *ed)
   return ed->metastack.last;
 }
 
+void SEQ_meta_stack_set(const Scene *scene, Sequence *seqm)
+{
+  Editing *ed = SEQ_editing_get(scene);
+  /* Clear metastack */
+  BLI_freelistN(&ed->metastack);
+
+  if (seqm != NULL) {
+    /* Allocate meta stack in a way, that represents meta hierarchy in timeline. */
+    seq_meta_stack_alloc(scene, seqm);
+    Sequence *meta_parent = seqm;
+    while (meta_parent = seq_sequence_lookup_meta_by_seq(scene, meta_parent)) {
+      seq_meta_stack_alloc(scene, meta_parent);
+    }
+
+    SEQ_seqbase_active_set(ed, &seqm->seqbase);
+    SEQ_channels_displayed_set(ed, &seqm->channels);
+  }
+  else {
+    /* Go to top level, exiting meta strip. */
+    SEQ_seqbase_active_set(ed, &ed->seqbase);
+    SEQ_channels_displayed_set(ed, &ed->channels);
+  }
+}
+
+Sequence *SEQ_meta_stack_pop(Editing *ed)
+{
+  MetaStack *ms = SEQ_meta_stack_active_get(ed);
+  Sequence *meta_parent = ms->parseq;
+  SEQ_seqbase_active_set(ed, ms->oldbasep);
+  SEQ_channels_displayed_set(ed, ms->old_channels);
+  BLI_remlink(&ed->metastack, ms);
+  MEM_freeN(ms);
+  return meta_parent;
+}
+
 /** \} */
 
 /* -------------------------------------------------------------------- */
diff --git a/source/blender/sequencer/intern/strip_edit.c b/source/blender/sequencer/intern/strip_edit.c
index bd439e3c9f8..4a88eab0fe2 100644
--- a/source/blender/sequencer/intern/strip_edit.c
+++ b/source/blender/sequencer/intern/strip_edit.c
@@ -192,19 +192,6 @@ void SEQ_edit_remove_flagged_sequences(Scene *scene, ListBase *seqbase)
   }
 }
 
-static bool seq_exists_in_seqbase(Sequence *seq, ListBase *seqbase)
-{
-  LISTBASE_FOREACH (Sequence *, seq_test, seqbase) {
-    if (seq_test->type == SEQ_TYPE_META && seq_exists_in_seqbase(seq, &seq_test->seqbase)) {
-      return true;
-    }
-    if (seq_test == seq) {
-      return true;
-    }
-  }
-  return false;
-}
-
 bool SEQ_edit_move_strip_to_seqbase(Scene *scene,
                                     ListBase *seqbase,
                                     Sequence *seq,
@@ -247,12 +234,12 @@ bool SEQ_edit_move_strip_to_meta(Scene *scene,
     return false;
   }
 
-  if (src_seq->type == SEQ_TYPE_META && seq_exists_in_seqbase(dst_seqm, &src_seq->seqbase)) {
+  if (src_seq->type == SEQ_TYPE_META && SEQ_exists_in_seqbase(dst_seqm, &src_seq->seqbase)) {
     *error_str = N_("Moved strip is parent of provided meta strip");
     return false;
   }
 
-  if (!seq_exists_in_seqbase(dst_seqm, &ed->seqbase)) {
+  if (!SEQ_exists_in_seqbase(dst_seqm, &ed->seqbase)) {
     *error_str = N_("Can not move strip to different scene");
     return false;
   }
diff --git a/source/blender/sequencer/intern/strip_relations.c b/source/blender/sequencer/intern/strip_relations.c
index 4acf2763ce5..a123212cb6e 100644
--- a/source/blender/sequencer/intern/strip_relations.c
+++ b/source/blender/sequencer/intern/strip_relations.c
@@ -457,3 +457,16 @@ struct Sequence *SEQ_find_metastrip_by_sequence(ListBase *seqbase, Sequence *met
 
   return NULL;
 }
+
+bool SEQ_exists_in_seqbase(const Sequence *seq, const ListBase *seqbase)
+{
+  LISTBASE_FOREACH (Sequence *, seq_test, seqbase) {
+    if (seq_test->type == SEQ_TYPE_META && SEQ_exists_in_seqbase(seq, &seq_test->seqbase)) {
+      return true;
+    }
+    if (seq_test == seq) {
+      return true;
+    }
+  }
+  return false;
+}