Fix #33253: VSE preview doesn't display compositor

There were two issues in scene strip rendering:

- It will skip rendering if scene doesn't have camera but uses compositor
- G.is_break will cancel preview rendering

Also removed Use Sequencer from scene's strip settings, it's not supported.

1 files changed, 9 insertions, 0 deletions

diff --git a/source/blender/editors/space_sequencer/sequencer_draw.c b/source/blender/editors/space_sequencer/sequencer_draw.c
index 37e57a1e850..5fefafaa54a 100644
--- a/source/blender/editors/space_sequencer/sequencer_draw.c
+++ b/source/blender/editors/space_sequencer/sequencer_draw.c
@@ -822,6 +822,7 @@ ImBuf *sequencer_ibuf_get(struct Main *bmain, Scene *scene, SpaceSeq *sseq, int
 	int rectx, recty;
 	float render_size = 0.0;
 	float proxy_size = 100.0;
+	short is_break = G.is_break;
 
 	render_size = sseq->render_size;
 	if (render_size == 0) {
@@ -840,6 +841,11 @@ ImBuf *sequencer_ibuf_get(struct Main *bmain, Scene *scene, SpaceSeq *sseq, int
 
 	context = BKE_sequencer_new_render_data(bmain, scene, rectx, recty, proxy_size);
 
+	/* sequencer could start rendering, in this case we need to be sure it wouldn't be canceled
+	 * by Esc pressed somewhere in the past
+	 */
+	G.is_break = FALSE;
+
 	if (special_seq_update)
 		ibuf = BKE_sequencer_give_ibuf_direct(context, cfra + frame_ofs, special_seq_update);
 	else if (!U.prefetchframes) // XXX || (G.f & G_PLAYANIM) == 0) {
@@ -847,6 +853,9 @@ ImBuf *sequencer_ibuf_get(struct Main *bmain, Scene *scene, SpaceSeq *sseq, int
 	else
 		ibuf = BKE_sequencer_give_ibuf_threaded(context, cfra + frame_ofs, sseq->chanshown);
 
+	/* restore state so real rendering would be canceled (if needed) */
+	G.is_break = is_break;
+
 	return ibuf;
 }