VSE: Implement the bounding box (xform) tool in the seq preview window

Make the "xform" tool/gizmo available for strip transformations in the
sequencer preview window.

Because of the amount of hacks needed to make the gizmo work nicely with
multiple strips at the same time, it was decided to only show the
translate gizmo when multiple strips are selected.

This is because the transforms with multiple strips would appear buggy
because of our lack of shearing support in the transform system.
There is also currently no way to properly sync the gizmo drawing with
the transform when using multiple strips.

Reviewed By: Richard Antalik, Campbell Barton

Differential Revision: http://developer.blender.org/D12729

1 files changed, 5 insertions, 0 deletions

diff --git a/source/blender/editors/space_sequencer/sequencer_draw.c b/source/blender/editors/space_sequencer/sequencer_draw.c
index e5e241c8b7e..6e4c3c774a2 100644
--- a/source/blender/editors/space_sequencer/sequencer_draw.c
+++ b/source/blender/editors/space_sequencer/sequencer_draw.c
@@ -2250,6 +2250,11 @@ void sequencer_draw_preview(const bContext *C,
   sequencer_draw_maskedit(C, scene, region, sseq);
 #endif
 
+  /* Draw registered callbacks. */
+  GPU_framebuffer_bind(framebuffer_overlay);
+  ED_region_draw_cb_draw(C, region, REGION_DRAW_POST_VIEW);
+  GPU_framebuffer_bind_no_srgb(framebuffer_overlay);
+
   /* Scope is freed in sequencer_check_scopes when `ibuf` changes and redraw is needed. */
   if (ibuf) {
     IMB_freeImBuf(ibuf);