VSE: Better handling of effect strip splitting

Splitting of effect strip alone wasn't handled properly. Previously
this resulted in duplicating effect strip, and it was broken at least
from 2.79.

Change in rB8ec6b34b8eb2 was intended to allow splitting strips
individually, so it can be used as RNA API function but also so it
requires as little glue logic as possible.

This is fixed by splitting all dependent strips at once in 2 separate
ListBases for left and right strips. Strips can be finally moved into
original `ListBase`.

With this fix it is still possible to split strips individually with
little glue logic. RNA API function could return list of split strips
as well, currently at least one strip in chain will be provided so
chain can be reconstructed on python side.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D10209

1 files changed, 58 insertions, 23 deletions

diff --git a/source/blender/sequencer/intern/strip_edit.c b/source/blender/sequencer/intern/strip_edit.c
index a26fb0244b6..b5b0dc2770e 100644
--- a/source/blender/sequencer/intern/strip_edit.c
+++ b/source/blender/sequencer/intern/strip_edit.c
@@ -39,6 +39,7 @@
 #include "BKE_sound.h"
 
 #include "strip_time.h"
+#include "utils.h"
 
 #include "SEQ_add.h"
 #include "SEQ_edit.h"
@@ -348,6 +349,29 @@ static void seq_split_set_left_offset(Sequence *seq, int timeline_frame)
   SEQ_transform_set_left_handle_frame(seq, timeline_frame);
 }
 
+static void seq_edit_split_handle_strip_offsets(Main *bmain,
+                                                Scene *scene,
+                                                Sequence *left_seq,
+                                                Sequence *right_seq,
+                                                const int timeline_frame,
+                                                const eSeqSplitMethod method)
+{
+  switch (method) {
+    case SEQ_SPLIT_SOFT:
+      seq_split_set_left_offset(right_seq, timeline_frame);
+      seq_split_set_right_offset(left_seq, timeline_frame);
+      break;
+    case SEQ_SPLIT_HARD:
+      seq_split_set_right_hold_offset(left_seq, timeline_frame);
+      seq_split_set_left_hold_offset(right_seq, timeline_frame);
+      SEQ_add_reload_new_file(bmain, scene, left_seq, false);
+      SEQ_add_reload_new_file(bmain, scene, right_seq, false);
+      break;
+  }
+  SEQ_time_update_sequence(scene, left_seq);
+  SEQ_time_update_sequence(scene, right_seq);
+}
+
 /**
  * Split Sequence at timeline_frame in two.
  *
@@ -370,33 +394,44 @@ Sequence *SEQ_edit_strip_split(Main *bmain,
     return NULL;
   }
 
-  if (method == SEQ_SPLIT_HARD) {
-    /* Precaution, needed because the length saved on-disk may not match the length saved in the
-     * blend file, or our code may have minor differences reading file length between versions.
-     * This causes hard-split to fail, see: T47862. */
-    SEQ_add_reload_new_file(bmain, scene, seq, true);
-    SEQ_time_update_sequence(scene, seq);
+  SeqCollection *collection = SEQ_collection_create();
+  SEQ_collection_append_strip(seq, collection);
+  SEQ_collection_expand(seqbase, collection, SEQ_query_strip_effect_chain);
+
+  /* Move strips in collection from seqbase to new ListBase. */
+  ListBase left_strips = {NULL, NULL};
+  SEQ_ITERATOR_FOREACH (seq, collection) {
+    BLI_remlink(seqbase, seq);
+    BLI_addtail(&left_strips, seq);
   }
 
-  Sequence *left_seq = seq;
-  Sequence *right_seq = SEQ_sequence_dupli_recursive(
-      scene, scene, seqbase, seq, SEQ_DUPE_UNIQUE_NAME | SEQ_DUPE_ANIM);
+  /* Sort list, so that no strip can depend on next strip in list.
+   * This is important for SEQ_time_update_sequence functionality. */
+  seq_sort_seqbase(&left_strips);
+
+  /* Duplicate ListBase. */
+  ListBase right_strips = {NULL, NULL};
+  SEQ_sequence_base_dupli_recursive(
+      scene, scene, &right_strips, &left_strips, SEQ_DUPE_ANIM | SEQ_DUPE_ALL, 0);
+
+  /* Split strips. */
+  Sequence *left_seq = left_strips.first;
+  Sequence *right_seq = right_strips.first;
+  Sequence *return_seq = right_strips.first;
+  while (left_seq && right_seq) {
+    seq_edit_split_handle_strip_offsets(bmain, scene, left_seq, right_seq, timeline_frame, method);
+    left_seq = left_seq->next;
+    right_seq = right_seq->next;
+  }
 
-  switch (method) {
-    case SEQ_SPLIT_SOFT:
-      seq_split_set_left_offset(right_seq, timeline_frame);
-      seq_split_set_right_offset(left_seq, timeline_frame);
-      break;
-    case SEQ_SPLIT_HARD:
-      seq_split_set_right_hold_offset(left_seq, timeline_frame);
-      seq_split_set_left_hold_offset(right_seq, timeline_frame);
-      SEQ_add_reload_new_file(bmain, scene, left_seq, false);
-      SEQ_add_reload_new_file(bmain, scene, right_seq, false);
-      break;
+  /* Move strips back to seqbase. Move right strips first, so left strips don't change name. */
+  BLI_movelisttolist(seqbase, &right_strips);
+  BLI_movelisttolist(seqbase, &left_strips);
+  LISTBASE_FOREACH (Sequence *, seq_iter, seqbase) {
+    SEQ_ensure_unique_name(seq_iter, scene);
   }
-  SEQ_time_update_sequence(scene, left_seq);
-  SEQ_time_update_sequence(scene, right_seq);
-  return right_seq;
+
+  return return_seq;
 }
 
 /**