VSE: Add precise drag and drop and strip previews

This patch adds the drag and drop strip previews in the VSE.
It also adds two new functions to the drag and drop API.

1. "draw_in_view" for callbacks that wants to draw elements in local viewport coordinates
2. "on_drag_start" that can be used for prefetching data only once at the start of the drag.

Reviewed By: Julian, Campbell

Differential Revision: http://developer.blender.org/D14560

1 files changed, 15 insertions, 0 deletions

diff --git a/source/blender/editors/include/ED_transform.h b/source/blender/editors/include/ED_transform.h
index 66c17ff8115..82cc518f029 100644
--- a/source/blender/editors/include/ED_transform.h
+++ b/source/blender/editors/include/ED_transform.h
@@ -202,6 +202,21 @@ int ED_transform_calc_gizmo_stats(const struct bContext *C,
                                   const struct TransformCalcParams *params,
                                   struct TransformBounds *tbounds);
 
+/**
+ * Iterates over all the strips and finds the closest snapping candidate of either \a frame_1 or \a
+ * frame_2. The closest snapping candidate will be the closest start or end frame of an existing
+ * strip.
+ * \returns True if there was anything to snap to.
+ */
+bool ED_transform_snap_sequencer_to_closest_strip_calc(struct Scene *scene,
+                                                       struct ARegion *region,
+                                                       int frame_1,
+                                                       int frame_2,
+                                                       int *r_snap_distance,
+                                                       float *r_snap_frame);
+
+void ED_draw_sequencer_snap_point(struct bContext *C, float snap_point);
+
 #ifdef __cplusplus
 }
 #endif