1 files changed, 78 insertions, 6 deletions

diff --git a/source/blender/editors/animation/anim_ops.c b/source/blender/editors/animation/anim_ops.c
index 72d9bff545a..6f3277397c5 100644
--- a/source/blender/editors/animation/anim_ops.c
+++ b/source/blender/editors/animation/anim_ops.c
@@ -51,8 +51,10 @@
 
 #include "DEG_depsgraph.h"
 
+#include "SEQ_iterator.h"
 #include "SEQ_sequencer.h"
 #include "SEQ_time.h"
+#include "SEQ_transform.h"
 
 #include "anim_intern.h"
 
@@ -81,6 +83,49 @@ static bool change_frame_poll(bContext *C)
   return false;
 }
 
+static int seq_snap_threshold_get_frame_distance(bContext *C)
+{
+  const int snap_distance = SEQ_tool_settings_snap_distance_get(CTX_data_scene(C));
+  const ARegion *region = CTX_wm_region(C);
+  return round_fl_to_int(UI_view2d_region_to_view_x(&region->v2d, snap_distance) -
+                         UI_view2d_region_to_view_x(&region->v2d, 0));
+}
+
+static void seq_frame_snap_update_best(const int position,
+                                       const int timeline_frame,
+                                       int *r_best_frame,
+                                       int *r_best_distance)
+{
+  if (abs(position - timeline_frame) < *r_best_distance) {
+    *r_best_distance = abs(position - timeline_frame);
+    *r_best_frame = position;
+  }
+}
+
+static int seq_frame_apply_snap(bContext *C, Scene *scene, const int timeline_frame)
+{
+
+  ListBase *seqbase = SEQ_active_seqbase_get(SEQ_editing_get(scene, false));
+  SeqCollection *strips = SEQ_query_all_strips(seqbase);
+
+  int best_frame = 0;
+  int best_distance = MAXFRAME;
+  Sequence *seq;
+  SEQ_ITERATOR_FOREACH (seq, strips) {
+    seq_frame_snap_update_best(
+        SEQ_transform_get_left_handle_frame(seq), timeline_frame, &best_frame, &best_distance);
+    seq_frame_snap_update_best(
+        SEQ_transform_get_right_handle_frame(seq), timeline_frame, &best_frame, &best_distance);
+  }
+  SEQ_collection_free(strips);
+
+  if (best_distance < seq_snap_threshold_get_frame_distance(C)) {
+    return best_frame;
+  }
+
+  return timeline_frame;
+}
+
 /* Set the new frame number */
 static void change_frame_apply(bContext *C, wmOperator *op)
 {
@@ -90,7 +135,7 @@ static void change_frame_apply(bContext *C, wmOperator *op)
 
   if (do_snap) {
     if (CTX_wm_space_seq(C)) {
-      frame = SEQ_time_find_next_prev_edit(scene, frame, SEQ_SIDE_BOTH, true, false, false);
+      frame = seq_frame_apply_snap(C, scene, frame);
     }
     else {
       frame = BKE_scene_frame_snap_by_seconds(scene, 1.0, frame);
@@ -181,6 +226,18 @@ static void change_frame_seq_preview_end(bContext *C)
   }
 }
 
+static bool use_sequencer_snapping(bContext *C)
+{
+  if (!CTX_wm_space_seq(C)) {
+    return false;
+  }
+
+  Scene *scene = CTX_data_scene(C);
+  short snap_flag = SEQ_tool_settings_snap_flag_get(scene);
+  return (scene->toolsettings->snap_flag & SCE_SNAP_SEQ) &&
+         (snap_flag & SEQ_SNAP_CURRENT_FRAME_TO_STRIPS);
+}
+
 /* Modal Operator init */
 static int change_frame_invoke(bContext *C, wmOperator *op, const wmEvent *event)
 {
@@ -190,6 +247,10 @@ static int change_frame_invoke(bContext *C, wmOperator *op, const wmEvent *event
    */
   RNA_float_set(op->ptr, "frame", frame_from_event(C, event));
 
+  if (use_sequencer_snapping(C)) {
+    RNA_boolean_set(op->ptr, "snap", true);
+  }
+
   change_frame_seq_preview_begin(C, event);
 
   change_frame_apply(C, op);
@@ -231,11 +292,22 @@ static int change_frame_modal(bContext *C, wmOperator *op, const wmEvent *event)
 
     case EVT_LEFTCTRLKEY:
     case EVT_RIGHTCTRLKEY:
-      if (event->val == KM_RELEASE) {
-        RNA_boolean_set(op->ptr, "snap", false);
+      /* Use Ctrl key to invert snapping in sequencer. */
+      if (use_sequencer_snapping(C)) {
+        if (event->val == KM_RELEASE) {
+          RNA_boolean_set(op->ptr, "snap", true);
+        }
+        else if (event->val == KM_PRESS) {
+          RNA_boolean_set(op->ptr, "snap", false);
+        }
       }
-      else if (event->val == KM_PRESS) {
-        RNA_boolean_set(op->ptr, "snap", true);
+      else {
+        if (event->val == KM_RELEASE) {
+          RNA_boolean_set(op->ptr, "snap", false);
+        }
+        else if (event->val == KM_PRESS) {
+          RNA_boolean_set(op->ptr, "snap", true);
+        }
       }
       break;
   }
@@ -465,7 +537,7 @@ static void ANIM_OT_previewrange_set(wmOperatorType *ot)
   /* rna */
   /* used to define frame range.
    *
-   * note: border Y values are not used,
+   * NOTE: border Y values are not used,
    * but are needed by box_select gesture operator stuff */
   WM_operator_properties_border(ot);
 }