Grease Pencil sketches get included when doing OpenGL previews for scene strips in sequencer

After double checking the sequencer code, there doesn't seem to be any reason to
exclude these from the sequencer previews. This makes it possible to use the
sequencer to non-destructively chain together difference Grease Pencil animated
shots together without having to render each image sequence first, allowing for
a smoother workflow.

Just in case the initial assumption isn't entirely correct, I've put in place
an extra arg to the relevant functions which can be hooked up to a suitable
option on the scene strip later to turn this on/off as needed.

6 files changed, 9 insertions, 6 deletions

diff --git a/source/blender/blenkernel/BKE_sequencer.h b/source/blender/blenkernel/BKE_sequencer.h
index 97cd5bd1bcb..5a0c7ac1ce1 100644
--- a/source/blender/blenkernel/BKE_sequencer.h
+++ b/source/blender/blenkernel/BKE_sequencer.h
@@ -393,7 +393,7 @@ struct Sequence *BKE_sequencer_add_sound_strip(struct bContext *C, ListBase *seq
 struct Sequence *BKE_sequencer_add_movie_strip(struct bContext *C, ListBase *seqbasep, struct SeqLoadInfo *seq_load);
 
 /* view3d draw callback, run when not in background view */
-typedef struct ImBuf *(*SequencerDrawView)(struct Scene *, struct Object *, int, int, unsigned int, int, bool, bool, int, char[256]);
+typedef struct ImBuf *(*SequencerDrawView)(struct Scene *, struct Object *, int, int, unsigned int, int, bool, bool, bool, int, char[256]);
 extern SequencerDrawView sequencer_view3d_cb;
 
 /* copy/paste */
diff --git a/source/blender/blenkernel/intern/sequencer.c b/source/blender/blenkernel/intern/sequencer.c
index 86a2b1d8b61..06eecc4b015 100644
--- a/source/blender/blenkernel/intern/sequencer.c
+++ b/source/blender/blenkernel/intern/sequencer.c
@@ -2586,7 +2586,7 @@ static ImBuf *seq_render_scene_strip(const SeqRenderData *context, Sequence *seq
 		ibuf = sequencer_view3d_cb(scene, camera, width, height, IB_rect,
 		                           context->scene->r.seq_prev_type,
 		                           (context->scene->r.seq_flag & R_SEQ_SOLID_TEX) != 0,
-		                           true, scene->r.alphamode, err_out);
+		                           true, true, scene->r.alphamode, err_out);
 		if (ibuf == NULL) {
 			fprintf(stderr, "seq_render_scene_strip failed to get opengl buffer: %s\n", err_out);
 		}
diff --git a/source/blender/editors/include/ED_view3d.h b/source/blender/editors/include/ED_view3d.h
index bd4f37cfb1e..76ad4ba7bdb 100644
--- a/source/blender/editors/include/ED_view3d.h
+++ b/source/blender/editors/include/ED_view3d.h
@@ -309,7 +309,7 @@ void ED_view3d_draw_offscreen(struct Scene *scene, struct View3D *v3d, struct AR
 struct ImBuf *ED_view3d_draw_offscreen_imbuf(struct Scene *scene, struct View3D *v3d, struct ARegion *ar, int sizex, int sizey, unsigned int flag,
                                              bool draw_background, int alpha_mode, char err_out[256]);
 struct ImBuf *ED_view3d_draw_offscreen_imbuf_simple(struct Scene *scene, struct Object *camera, int width, int height, unsigned int flag, int drawtype,
-                                                    bool use_solid_tex, bool draw_background, int alpha_mode, char err_out[256]);
+                                                    bool use_solid_tex, bool use_gpencil, bool draw_background, int alpha_mode, char err_out[256]);
 void ED_view3d_offscreen_sky_color_get(struct Scene *scene, float sky_color[3]);
 
 struct Base *ED_view3d_give_base_under_cursor(struct bContext *C, const int mval[2]);
diff --git a/source/blender/editors/render/render_opengl.c b/source/blender/editors/render/render_opengl.c
index 433630f6ed4..7df281b70bd 100644
--- a/source/blender/editors/render/render_opengl.c
+++ b/source/blender/editors/render/render_opengl.c
@@ -272,7 +272,7 @@ static void screen_opengl_render_apply(OGLRender *oglrender)
 		/* shouldnt suddenly give errors mid-render but possible */
 		char err_out[256] = "unknown";
 		ImBuf *ibuf_view = ED_view3d_draw_offscreen_imbuf_simple(scene, scene->camera, oglrender->sizex, oglrender->sizey,
-		                                                         IB_rect, OB_SOLID, false, true,
+		                                                         IB_rect, OB_SOLID, false, true, true,
 		                                                         (draw_sky) ? R_ADDSKY : R_ALPHAPREMUL, err_out);
 		camera = scene->camera;
 
diff --git a/source/blender/editors/space_view3d/view3d_draw.c b/source/blender/editors/space_view3d/view3d_draw.c
index bc5ef14e8bc..9a815976073 100644
--- a/source/blender/editors/space_view3d/view3d_draw.c
+++ b/source/blender/editors/space_view3d/view3d_draw.c
@@ -3147,7 +3147,7 @@ ImBuf *ED_view3d_draw_offscreen_imbuf(Scene *scene, View3D *v3d, ARegion *ar, in
 
 /* creates own 3d views, used by the sequencer */
 ImBuf *ED_view3d_draw_offscreen_imbuf_simple(Scene *scene, Object *camera, int width, int height, unsigned int flag, int drawtype,
-                                             bool use_solid_tex, bool draw_background, int alpha_mode, char err_out[256])
+                                             bool use_solid_tex, bool use_gpencil, bool draw_background, int alpha_mode, char err_out[256])
 {
 	View3D v3d = {NULL};
 	ARegion ar = {NULL};
@@ -3162,6 +3162,9 @@ ImBuf *ED_view3d_draw_offscreen_imbuf_simple(Scene *scene, Object *camera, int w
 	v3d.lay = scene->lay;
 	v3d.drawtype = drawtype;
 	v3d.flag2 = V3D_RENDER_OVERRIDE;
+	
+	if (use_gpencil)
+		v3d.flag2 |= V3D_SHOW_GPENCIL;
 
 	if (use_solid_tex)
 		v3d.flag2 |= V3D_SOLID_TEX;
diff --git a/source/blender/windowmanager/intern/wm_files.c b/source/blender/windowmanager/intern/wm_files.c
index 412d65dc5ca..c1c31f6795d 100644
--- a/source/blender/windowmanager/intern/wm_files.c
+++ b/source/blender/windowmanager/intern/wm_files.c
@@ -840,7 +840,7 @@ static ImBuf *blend_file_thumb(Scene *scene, bScreen *screen, int **thumb_pt)
 	if (scene->camera) {
 		ibuf = ED_view3d_draw_offscreen_imbuf_simple(scene, scene->camera,
 		                                             BLEN_THUMB_SIZE * 2, BLEN_THUMB_SIZE * 2,
-		                                             IB_rect, OB_SOLID, false, false, R_ADDSKY, err_out);
+		                                             IB_rect, OB_SOLID, false, false, false, R_ADDSKY, err_out);
 	}
 	else {
 		ibuf = ED_view3d_draw_offscreen_imbuf(scene, v3d, ar, BLEN_THUMB_SIZE * 2, BLEN_THUMB_SIZE * 2,