VSE: Refactor delete operator and API

Operator logic is limited to iterating over selection and executing
same code as python API does.

Functional changes:

 - No attempt to preserve effects is made. Dependant effects are deleted.
 - No attempt to change meta strip boundaries.

Partially fixes T73828

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D6892

4 files changed, 70 insertions, 118 deletions

diff --git a/source/blender/blenkernel/BKE_sequencer.h b/source/blender/blenkernel/BKE_sequencer.h
index c32abbb41c6..2873a13d1f7 100644
--- a/source/blender/blenkernel/BKE_sequencer.h
+++ b/source/blender/blenkernel/BKE_sequencer.h
@@ -625,6 +625,10 @@ void BKE_sequencer_color_balance_apply(struct StripColorBalance *cb,
 void BKE_sequencer_all_free_anim_ibufs(struct Scene *scene, int cfra);
 bool BKE_sequencer_check_scene_recursion(struct Scene *scene, struct ReportList *reports);
 bool BKE_sequencer_render_loop_check(struct Sequence *seq_main, struct Sequence *seq);
+void BKE_sequencer_flag_for_removal(struct Scene *scene,
+                                    struct ListBase *seqbase,
+                                    struct Sequence *seq);
+void BKE_sequencer_remove_flagged_sequences(struct Scene *scene, struct ListBase *seqbase);
 
 #ifdef __cplusplus
 }
diff --git a/source/blender/blenkernel/intern/sequencer.c b/source/blender/blenkernel/intern/sequencer.c
index 742b20c7de9..4b2d42c704e 100644
--- a/source/blender/blenkernel/intern/sequencer.c
+++ b/source/blender/blenkernel/intern/sequencer.c
@@ -6069,3 +6069,61 @@ bool BKE_sequencer_render_loop_check(Sequence *seq_main, Sequence *seq)
 
   return false;
 }
+
+static void sequencer_flag_users_for_removal(Scene *scene, ListBase *seqbase, Sequence *seq)
+{
+  LISTBASE_FOREACH (Sequence *, user_seq, seqbase) {
+    /* Look in metas for usage of seq. */
+    if (user_seq->type == SEQ_TYPE_META) {
+      sequencer_flag_users_for_removal(scene, &user_seq->seqbase, seq);
+    }
+
+    /* Clear seq from modifiers. */
+    SequenceModifierData *smd;
+    for (smd = user_seq->modifiers.first; smd; smd = smd->next) {
+      if (smd->mask_sequence == seq) {
+        smd->mask_sequence = NULL;
+      }
+    }
+
+    /* Remove effects, that use seq. */
+    if ((user_seq->seq1 && user_seq->seq1 == seq) || (user_seq->seq2 && user_seq->seq2 == seq) ||
+        (user_seq->seq3 && user_seq->seq3 == seq)) {
+      user_seq->flag |= SEQ_FLAG_DELETE;
+      /* Strips can be used as mask even if not in same seqbase. */
+      sequencer_flag_users_for_removal(scene, &scene->ed->seqbase, user_seq);
+    }
+  }
+}
+
+/* Flag seq and its users (effects) for removal. */
+void BKE_sequencer_flag_for_removal(Scene *scene, ListBase *seqbase, Sequence *seq)
+{
+  if (seq == NULL || (seq->flag & SEQ_FLAG_DELETE) != 0) {
+    return;
+  }
+
+  /* Flag and remove meta children. */
+  if (seq->type == SEQ_TYPE_META) {
+    LISTBASE_FOREACH (Sequence *, meta_child, &seq->seqbase) {
+      BKE_sequencer_flag_for_removal(scene, &seq->seqbase, meta_child);
+    }
+  }
+
+  seq->flag |= SEQ_FLAG_DELETE;
+  sequencer_flag_users_for_removal(scene, seqbase, seq);
+}
+
+/* Remove all flagged sequences, return true if sequence is removed. */
+void BKE_sequencer_remove_flagged_sequences(Scene *scene, ListBase *seqbase)
+{
+  LISTBASE_FOREACH_MUTABLE (Sequence *, seq, seqbase) {
+    if (seq->flag & SEQ_FLAG_DELETE) {
+      if (seq->type == SEQ_TYPE_META) {
+        BKE_sequencer_remove_flagged_sequences(scene, &seq->seqbase);
+      }
+      BLI_remlink(seqbase, seq);
+      BKE_sequence_free(scene, seq, true);
+    }
+  }
+}
diff --git a/source/blender/editors/space_sequencer/sequencer_edit.c b/source/blender/editors/space_sequencer/sequencer_edit.c
index ce4fc0ff538..604d2f2a108 100644
--- a/source/blender/editors/space_sequencer/sequencer_edit.c
+++ b/source/blender/editors/space_sequencer/sequencer_edit.c
@@ -666,74 +666,6 @@ int seq_effect_find_selected(Scene *scene,
 /** \name Delete Utilities
  * \{ */
 
-static Sequence *del_seq_find_replace_recurs(Scene *scene, Sequence *seq)
-{
-  Sequence *seq1, *seq2, *seq3;
-
-  /* Try to find a replacement input sequence, and flag for later deletion if
-   * no replacement can be found. */
-
-  if (!seq) {
-    return NULL;
-  }
-  if (!(seq->type & SEQ_TYPE_EFFECT)) {
-    return ((seq->flag & SELECT) ? NULL : seq);
-  }
-  if (!(seq->flag & SELECT)) {
-    /* Try to find replacement for effect inputs. */
-    seq1 = del_seq_find_replace_recurs(scene, seq->seq1);
-    seq2 = del_seq_find_replace_recurs(scene, seq->seq2);
-    seq3 = del_seq_find_replace_recurs(scene, seq->seq3);
-
-    if (seq1 == seq->seq1 && seq2 == seq->seq2 && seq3 == seq->seq3) {
-      /* Pass. */
-    }
-    else if (seq1 || seq2 || seq3) {
-      seq->seq1 = (seq1) ? seq1 : (seq2) ? seq2 : seq3;
-      seq->seq2 = (seq2) ? seq2 : (seq1) ? seq1 : seq3;
-      seq->seq3 = (seq3) ? seq3 : (seq1) ? seq1 : seq2;
-
-      BKE_sequencer_update_changed_seq_and_deps(scene, seq, 1, 1);
-    }
-    else {
-      seq->flag |= SELECT; /* Mark for delete. */
-    }
-  }
-
-  if (seq->flag & SELECT) {
-    if ((seq1 = del_seq_find_replace_recurs(scene, seq->seq1))) {
-      return seq1;
-    }
-    if ((seq2 = del_seq_find_replace_recurs(scene, seq->seq2))) {
-      return seq2;
-    }
-    if ((seq3 = del_seq_find_replace_recurs(scene, seq->seq3))) {
-      return seq3;
-    }
-    return NULL;
-  }
-  return seq;
-}
-
-static void del_seq_clear_modifiers_recurs(Scene *scene, Sequence *deleting_sequence)
-{
-  Editing *ed = BKE_sequencer_editing_get(scene, false);
-  Sequence *current_sequence;
-
-  SEQP_BEGIN (ed, current_sequence) {
-    if (!(current_sequence->flag & SELECT) && current_sequence != deleting_sequence) {
-      SequenceModifierData *smd;
-
-      for (smd = current_sequence->modifiers.first; smd; smd = smd->next) {
-        if (smd->mask_sequence == deleting_sequence) {
-          smd->mask_sequence = NULL;
-        }
-      }
-    }
-  }
-  SEQ_END;
-}
-
 static void recurs_del_seq_flag(Scene *scene, ListBase *lb, short flag, short deleteall)
 {
   Sequence *seq, *seqn;
@@ -2582,61 +2514,18 @@ static int sequencer_delete_exec(bContext *C, wmOperator *UNUSED(op))
   Scene *scene = CTX_data_scene(C);
   Editing *ed = BKE_sequencer_editing_get(scene, false);
   Sequence *seq;
-  MetaStack *ms;
-  bool nothing_selected = true;
-
-  BKE_sequencer_prefetch_stop(scene);
-
-  seq = BKE_sequencer_active_get(scene);
-  if (seq && seq->flag & SELECT) { /* Avoid a loop since this is likely to be selected. */
-    nothing_selected = false;
-  }
-  else {
-    for (seq = ed->seqbasep->first; seq; seq = seq->next) {
-      if (seq->flag & SELECT) {
-        nothing_selected = false;
-        break;
-      }
-    }
-  }
-
-  if (nothing_selected) {
-    return OPERATOR_FINISHED;
-  }
 
-  /* For effects and modifiers, try to find a replacement input. */
-  for (seq = ed->seqbasep->first; seq; seq = seq->next) {
-    if (!(seq->flag & SELECT)) {
-      if ((seq->type & SEQ_TYPE_EFFECT)) {
-        del_seq_find_replace_recurs(scene, seq);
-      }
-    }
-    else {
-      del_seq_clear_modifiers_recurs(scene, seq);
+  SEQP_BEGIN (scene->ed, seq) {
+    if (seq->flag & SELECT) {
+      BKE_sequencer_flag_for_removal(scene, ed->seqbasep, seq);
     }
   }
-
-  /* Delete all selected strips. */
-  recurs_del_seq_flag(scene, ed->seqbasep, SELECT, 0);
-
-  /* Update lengths, etc. */
-  seq = ed->seqbasep->first;
-  while (seq) {
-    BKE_sequence_calc(scene, seq);
-    seq = seq->next;
-  }
-
-  /* Free parent metas. */
-  ms = ed->metastack.last;
-  while (ms) {
-    BKE_sequence_calc(scene, ms->parseq);
-    ms = ms->prev;
-  }
+  SEQ_END;
+  BKE_sequencer_remove_flagged_sequences(scene, ed->seqbasep);
 
   DEG_id_tag_update(&scene->id, ID_RECALC_SEQUENCER_STRIPS);
   DEG_relations_tag_update(bmain);
   WM_event_add_notifier(C, NC_SCENE | ND_SEQUENCER, scene);
-
   return OPERATOR_FINISHED;
 }
 
diff --git a/source/blender/makesrna/intern/rna_sequencer_api.c b/source/blender/makesrna/intern/rna_sequencer_api.c
index 4157747455d..59cedf8fcb8 100644
--- a/source/blender/makesrna/intern/rna_sequencer_api.c
+++ b/source/blender/makesrna/intern/rna_sequencer_api.c
@@ -370,13 +370,14 @@ static void rna_Sequences_remove(
   Sequence *seq = seq_ptr->data;
   Scene *scene = (Scene *)id;
 
-  if (BLI_remlink_safe(&ed->seqbase, seq) == false) {
+  if (BLI_findindex(&ed->seqbase, seq) == -1) {
     BKE_reportf(
         reports, RPT_ERROR, "Sequence '%s' not in scene '%s'", seq->name + 2, scene->id.name + 2);
     return;
   }
 
-  BKE_sequence_free(scene, seq, true);
+  BKE_sequencer_flag_for_removal(scene, &ed->seqbase, seq);
+  BKE_sequencer_remove_flagged_sequences(scene, &ed->seqbase);
   RNA_POINTER_INVALIDATE(seq_ptr);
 
   DEG_relations_tag_update(bmain);