VSE: Reduce transform code complexity

Reduce complexity of sequencer transform code by removing recursivity.
This is possible by treating meta strips (mostly) as any other strip and
containing all transform code within SEQ_ functions.

Unfortunately internally meta strips still require special treatment,
but all complexity from code all over transform code seems to be
possible to contain within one function.

Functional change:
Previously adjusting handle of single image strip moved animation.
Now animation is not moved, which is behavior for all other strips.

Reviewed By: sergey, mano-wii

Differential Revision: https://developer.blender.org/D11493

3 files changed, 12 insertions, 3 deletions

diff --git a/source/blender/sequencer/SEQ_time.h b/source/blender/sequencer/SEQ_time.h
index 67d3a2e5960..593a8fe7bf2 100644
--- a/source/blender/sequencer/SEQ_time.h
+++ b/source/blender/sequencer/SEQ_time.h
@@ -46,6 +46,7 @@ void SEQ_time_update_sequence(struct Scene *scene, struct Sequence *seq);
 void SEQ_time_update_sequence_bounds(struct Scene *scene, struct Sequence *seq);
 int SEQ_time_cmp_time_startdisp(const void *a, const void *b);
 bool SEQ_time_strip_intersects_frame(const struct Sequence *seq, const int timeline_frame);
+void SEQ_time_update_meta_strip_range(struct Scene *scene, struct Sequence *seq_meta);
 
 #ifdef __cplusplus
 }
diff --git a/source/blender/sequencer/intern/strip_time.c b/source/blender/sequencer/intern/strip_time.c
index b8b6f62c7aa..65756006fa9 100644
--- a/source/blender/sequencer/intern/strip_time.c
+++ b/source/blender/sequencer/intern/strip_time.c
@@ -184,7 +184,7 @@ static void seq_time_update_meta_strip(Scene *scene, Sequence *seq_meta)
   seq_update_sound_bounds_recursive(scene, seq_meta);
 }
 
-static void seq_time_update_meta_strip_range(Scene *scene, Sequence *seq_meta)
+void SEQ_time_update_meta_strip_range(Scene *scene, Sequence *seq_meta)
 {
   seq_time_update_meta_strip(scene, seq_meta);
 
@@ -250,7 +250,7 @@ void SEQ_time_update_sequence(Scene *scene, Sequence *seq)
     Editing *ed = SEQ_editing_get(scene, false);
     MetaStack *ms = SEQ_meta_stack_active_get(ed);
     if (ms != NULL) {
-      seq_time_update_meta_strip_range(scene, ms->parseq);
+      SEQ_time_update_meta_strip_range(scene, ms->parseq);
     }
 
     SEQ_time_update_sequence_bounds(scene, seq);
diff --git a/source/blender/sequencer/intern/strip_transform.c b/source/blender/sequencer/intern/strip_transform.c
index a02d8a1428e..b969f531e68 100644
--- a/source/blender/sequencer/intern/strip_transform.c
+++ b/source/blender/sequencer/intern/strip_transform.c
@@ -233,14 +233,22 @@ void SEQ_transform_translate_sequence(Scene *evil_scene, Sequence *seq, int delt
   SEQ_offset_animdata(evil_scene, seq, delta);
   seq->start += delta;
 
+  /* Meta strips requires special handling: their content is to be translated, and then frame range
+   * of the meta is to be updated for the updated content. */
   if (seq->type == SEQ_TYPE_META) {
     Sequence *seq_child;
     for (seq_child = seq->seqbase.first; seq_child; seq_child = seq_child->next) {
       SEQ_transform_translate_sequence(evil_scene, seq_child, delta);
     }
+    /* Ensure that meta bounds are updated, but this function prevents resets seq->start and
+     * start/end point in timeline. */
+    SEQ_time_update_meta_strip_range(evil_scene, seq);
+    /* Move meta start/end points. */
+    SEQ_transform_set_left_handle_frame(seq, seq->startdisp + delta);
+    SEQ_transform_set_right_handle_frame(seq, seq->enddisp + delta);
   }
 
-  SEQ_time_update_sequence_bounds(evil_scene, seq);
+  SEQ_time_update_sequence(evil_scene, seq);
 }
 
 /* return 0 if there weren't enough space */