GPencil: Use default material when slot material is empty

When a material slot is empty, the default material is used.

The default color used is Gray to get a good contrast in dense scenes with dark and white background.

Reviewers: brecht, dfelinto, mendio, pepeland

Differential Revision: https://developer.blender.org/D5625

1 files changed, 8 insertions, 0 deletions

diff --git a/source/blender/editors/gpencil/gpencil_paint.c b/source/blender/editors/gpencil/gpencil_paint.c
index 900883bd0af..3217c94eebd 100644
--- a/source/blender/editors/gpencil/gpencil_paint.c
+++ b/source/blender/editors/gpencil/gpencil_paint.c
@@ -1244,6 +1244,14 @@ static void gp_stroke_newfrombuffer(tGPsdata *p)
 
   /* Save material index */
   gps->mat_nr = BKE_gpencil_object_material_get_index_from_brush(p->ob, p->brush);
+  if (gps->mat_nr < 0) {
+    if (p->ob->actcol - 1 < 0) {
+      gps->mat_nr = 0;
+    }
+    else {
+      gps->mat_nr = p->ob->actcol - 1;
+    }
+  }
 
   /* calculate UVs along the stroke */
   ED_gpencil_calc_stroke_uv(obact, gps);