VSE: Move remove gaps operator logic to module code

Logic was broken into finding gaps and ofsetting strips.
Functions were modified so they work on explicitly defined seqbase,
so they can be used as python API functions.

Functional changes:
 - Improve performance by calculating gap length and offseting strips
   at once. Previously strips were offset by one frame.
 - Calculate gap from start frame. Previously gap was considered only
   inbetween strips.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D9730

1 files changed, 12 insertions, 0 deletions

diff --git a/source/blender/sequencer/intern/strip_time.h b/source/blender/sequencer/intern/strip_time.h
index e4fb7f1d2ec..e435ff1ec5d 100644
--- a/source/blender/sequencer/intern/strip_time.h
+++ b/source/blender/sequencer/intern/strip_time.h
@@ -29,10 +29,22 @@ extern "C" {
 
 struct Scene;
 struct Sequence;
+struct ListBase;
 
 float seq_give_frame_index(struct Sequence *seq, float timeline_frame);
 void seq_update_sound_bounds_recursive(struct Scene *scene, struct Sequence *metaseq);
 
+/* Describes gap between strips in timeline. */
+typedef struct GapInfo {
+  int gap_start_frame; /* Start frame of the gap. */
+  int gap_length;      /* Length of the gap. */
+  bool gap_exists;     /* False if there are no gaps. */
+} GapInfo;
+void seq_time_gap_info_get(const struct Scene *scene,
+                           struct ListBase *seqbase,
+                           const int initial_frame,
+                           struct GapInfo *r_gap_info);
+
 #ifdef __cplusplus
 }
 #endif