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

7 files changed, 107 insertions, 46 deletions

diff --git a/source/blender/editors/space_sequencer/sequencer_edit.c b/source/blender/editors/space_sequencer/sequencer_edit.c
index 16f663110ec..76dd43586d1 100644
--- a/source/blender/editors/space_sequencer/sequencer_edit.c
+++ b/source/blender/editors/space_sequencer/sequencer_edit.c
@@ -1911,11 +1911,9 @@ static int sequencer_meta_toggle_exec(bContext *C, wmOperator *UNUSED(op))
   SEQ_prefetch_stop(scene);
 
   if (active_seq && active_seq->type == SEQ_TYPE_META && active_seq->flag & SELECT) {
-    /* Enter meta-strip. */
-    SEQ_meta_stack_alloc(ed, active_seq);
-    SEQ_seqbase_active_set(ed, &active_seq->seqbase);
-    SEQ_channels_displayed_set(ed, &active_seq->channels);
+    /* Deselect active meta seq. */
     SEQ_select_active_set(scene, NULL);
+    SEQ_meta_stack_set(scene, active_seq);
   }
   else {
     /* Exit meta-strip if possible. */
@@ -1923,14 +1921,12 @@ static int sequencer_meta_toggle_exec(bContext *C, wmOperator *UNUSED(op))
       return OPERATOR_CANCELLED;
     }
 
-    MetaStack *ms = SEQ_meta_stack_active_get(ed);
-    SEQ_seqbase_active_set(ed, ms->oldbasep);
-    SEQ_channels_displayed_set(ed, ms->old_channels);
-    SEQ_select_active_set(scene, ms->parseq);
-    SEQ_meta_stack_free(ed, ms);
+    /* Display parent meta. */
+    Sequence *meta_parent = SEQ_meta_stack_pop(ed);
+    SEQ_select_active_set(scene, meta_parent);
   }
 
-  DEG_id_tag_update(&scene->id, ID_RECALC_SEQUENCER_STRIPS);
+  // DEG_id_tag_update(&scene->id, ID_RECALC_SEQUENCER_STRIPS);
   WM_event_add_notifier(C, NC_SCENE | ND_SEQUENCER, scene);
 
   return OPERATOR_FINISHED;
diff --git a/source/blender/makesrna/intern/rna_sequencer.c b/source/blender/makesrna/intern/rna_sequencer.c
index 100d90df5d6..9bfdcda79a7 100644
--- a/source/blender/makesrna/intern/rna_sequencer.c
+++ b/source/blender/makesrna/intern/rna_sequencer.c
@@ -43,6 +43,7 @@
 #include "SEQ_prefetch.h"
 #include "SEQ_proxy.h"
 #include "SEQ_relations.h"
+#include "SEQ_select.h"
 #include "SEQ_sequencer.h"
 #include "SEQ_sound.h"
 #include "SEQ_time.h"
@@ -1107,6 +1108,26 @@ static void rna_SequenceEditor_overlay_frame_set(PointerRNA *ptr, int value)
   }
 }
 
+static void rna_SequenceEditor_display_stack(ID *id,
+                                             Editing *ed,
+                                             ReportList *reports,
+                                             Sequence *seqm)
+{
+  /* Check for non-meta sequence */
+  if (seqm != NULL && seqm->type != SEQ_TYPE_META && SEQ_exists_in_seqbase(seqm, &ed->seqbase)) {
+    BKE_report(reports, RPT_ERROR, "Sequence type must be 'META'");
+    return;
+  }
+
+  /* Get editing base of meta sequence */
+  Scene *scene = (Scene *)id;
+  SEQ_meta_stack_set(scene, seqm);
+  /* De-activate strip. This is to prevent strip from different timeline being drawn. */
+  SEQ_select_active_set(scene, NULL);
+
+  WM_main_add_notifier(NC_SCENE | ND_SEQUENCER, scene);
+}
+
 static bool modifier_seq_cmp_fn(Sequence *seq, void *arg_pt)
 {
   SequenceSearchData *data = arg_pt;
@@ -2116,6 +2137,8 @@ static void rna_def_channel(BlenderRNA *brna)
 static void rna_def_editor(BlenderRNA *brna)
 {
   StructRNA *srna;
+  FunctionRNA *func;
+  PropertyRNA *parm;
   PropertyRNA *prop;
 
   static const EnumPropertyItem editing_storage_items[] = {
@@ -2259,6 +2282,15 @@ static void rna_def_editor(BlenderRNA *brna)
       "Prefetch Frames",
       "Render frames ahead of current frame in the background for faster playback");
   RNA_def_property_update(prop, NC_SCENE | ND_SEQUENCER, NULL);
+
+  /* functions */
+
+  func = RNA_def_function(srna, "display_stack", "rna_SequenceEditor_display_stack");
+  RNA_def_function_flag(func, FUNC_USE_SELF_ID | FUNC_USE_REPORTS);
+  RNA_def_function_ui_description(func, "Display sequences stack");
+  parm = RNA_def_pointer(
+      func, "meta_sequence", "Sequence", "Meta Sequence", "Meta to display its stack");
+  RNA_def_parameter_flags(parm, 0, PARM_REQUIRED);
 }
 
 static void rna_def_filter_video(StructRNA *srna)
diff --git a/source/blender/sequencer/SEQ_relations.h b/source/blender/sequencer/SEQ_relations.h
index 917f549f16d..9678ac1cc1c 100644
--- a/source/blender/sequencer/SEQ_relations.h
+++ b/source/blender/sequencer/SEQ_relations.h
@@ -68,6 +68,7 @@ void SEQ_cache_iterate(
 struct Sequence *SEQ_find_metastrip_by_sequence(ListBase *seqbase /* = ed->seqbase */,
                                                 struct Sequence *meta /* = NULL */,
                                                 struct Sequence *seq);
+bool SEQ_exists_in_seqbase(const struct Sequence *seq, const struct ListBase *seqbase);
 
 #ifdef __cplusplus
 }
diff --git a/source/blender/sequencer/SEQ_sequencer.h b/source/blender/sequencer/SEQ_sequencer.h
index 70cba58007f..a77ca1c7baf 100644
--- a/source/blender/sequencer/SEQ_sequencer.h
+++ b/source/blender/sequencer/SEQ_sequencer.h
@@ -70,27 +70,24 @@ void SEQ_seqbase_active_set(struct Editing *ed, struct ListBase *seqbase);
 struct Sequence *SEQ_sequence_alloc(ListBase *lb, int timeline_frame, int machine, int type);
 void SEQ_sequence_free(struct Scene *scene, struct Sequence *seq);
 /**
- * Create and initialize #MetaStack, append it to `ed->metastack` ListBase
+ * Get #MetaStack that corresponds to current level that is being viewed
  *
- * \param ed: sequence editor data
- * \param seq_meta: meta strip
- * \return pointer to created meta stack
+ * \return pointer to meta stack
  */
-struct MetaStack *SEQ_meta_stack_alloc(struct Editing *ed, struct Sequence *seq_meta);
+struct MetaStack *SEQ_meta_stack_active_get(const struct Editing *ed);
 /**
- * Get #MetaStack that corresponds to current level that is being viewed
+ * Open Meta strip content for editing.
  *
  * \param ed: sequence editor data
- * \return pointer to meta stack
+ * \param seqm: meta sequence or NULL for top level view
  */
-struct MetaStack *SEQ_meta_stack_active_get(const struct Editing *ed);
+void SEQ_meta_stack_set(const struct Scene *scene, struct Sequence *dst_seq);
 /**
- * Free #MetaStack and remove it from `ed->metastack` ListBase.
+ * Close last Meta strip open for editing.
  *
  * \param ed: sequence editor data
- * \param ms: meta stack
  */
-void SEQ_meta_stack_free(struct Editing *ed, struct MetaStack *ms);
+struct Sequence *SEQ_meta_stack_pop(struct Editing *ed);
 struct Sequence *SEQ_sequence_dupli_recursive(const struct Scene *scene_src,
                                               struct Scene *scene_dst,
                                               struct ListBase *new_seq_list,
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;
+}