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

15 files changed, 129 insertions, 49 deletions

diff --git a/release/scripts/startup/bl_ui/properties_grease_pencil_common.py b/release/scripts/startup/bl_ui/properties_grease_pencil_common.py
index 9c8f62fb906..b41be13555c 100644
--- a/release/scripts/startup/bl_ui/properties_grease_pencil_common.py
+++ b/release/scripts/startup/bl_ui/properties_grease_pencil_common.py
@@ -892,7 +892,8 @@ class GreasePencilMaterialsPanel:
             if is_view3d and brush is not None:
                 gp_settings = brush.gpencil_settings
                 if gp_settings.use_material_pin is False:
-                    ma = ob.material_slots[ob.active_material_index].material
+                    if ob.active_material_index > 0:
+                        ma = ob.material_slots[ob.active_material_index].material
                 else:
                     ma = gp_settings.material
 
diff --git a/source/blender/blenkernel/BKE_gpencil.h b/source/blender/blenkernel/BKE_gpencil.h
index f1cf87ea1b5..75e98ee31de 100644
--- a/source/blender/blenkernel/BKE_gpencil.h
+++ b/source/blender/blenkernel/BKE_gpencil.h
@@ -155,7 +155,7 @@ struct Material *BKE_gpencil_brush_material_get(struct Brush *brush);
 void BKE_gpencil_brush_material_set(struct Brush *brush, struct Material *material);
 
 /* Object */
-struct Material *BKE_gpencil_object_material_ensure_active(struct Main *bmain, struct Object *ob);
+struct Material *BKE_gpencil_object_material_ensure_active(struct Object *ob);
 struct Material *BKE_gpencil_object_material_ensure_from_brush(struct Main *bmain,
                                                                struct Object *ob,
                                                                struct Brush *brush);
@@ -179,8 +179,7 @@ struct Material *BKE_gpencil_object_material_ensure_from_active_input_toolsettin
 struct Material *BKE_gpencil_object_material_ensure_from_active_input_brush(struct Main *bmain,
                                                                             struct Object *ob,
                                                                             struct Brush *brush);
-struct Material *BKE_gpencil_object_material_ensure_from_active_input_material(struct Main *bmain,
-                                                                               struct Object *ob);
+struct Material *BKE_gpencil_object_material_ensure_from_active_input_material(struct Object *ob);
 
 /* object boundbox */
 bool BKE_gpencil_data_minmax(const struct bGPdata *gpd, float r_min[3], float r_max[3]);
diff --git a/source/blender/blenkernel/BKE_material.h b/source/blender/blenkernel/BKE_material.h
index 44a8f98e994..7ff9c4e6376 100644
--- a/source/blender/blenkernel/BKE_material.h
+++ b/source/blender/blenkernel/BKE_material.h
@@ -38,6 +38,7 @@ struct bNode;
 /* materials */
 
 void init_def_material(void);
+void BKE_material_gpencil_default_free(void);
 void BKE_material_free(struct Material *ma);
 void test_object_materials(struct Main *bmain, struct Object *ob, struct ID *id);
 void test_all_objects_materials(struct Main *bmain, struct ID *id);
@@ -46,6 +47,7 @@ void BKE_material_resize_object(struct Main *bmain,
                                 const short totcol,
                                 bool do_id_user);
 void BKE_material_init(struct Material *ma);
+void BKE_material_gpencil_init(struct Material *ma);
 void BKE_material_remap_object(struct Object *ob, const unsigned int *remap);
 void BKE_material_remap_object_calc(struct Object *ob_dst,
                                     struct Object *ob_src,
@@ -92,6 +94,7 @@ bool BKE_object_material_slot_add(struct Main *bmain, struct Object *ob);
 bool BKE_object_material_slot_remove(struct Main *bmain, struct Object *ob);
 bool BKE_object_material_slot_used(struct ID *id, short actcol);
 
+struct Material *BKE_material_gpencil_get(struct Object *ob, short act);
 struct MaterialGPencilStyle *BKE_material_gpencil_settings_get(struct Object *ob, short act);
 
 void BKE_texpaint_slot_refresh_cache(struct Scene *scene, struct Material *ma);
@@ -123,6 +126,7 @@ struct Depsgraph;
 void BKE_material_eval(struct Depsgraph *depsgraph, struct Material *material);
 
 extern struct Material defmaterial;
+extern struct Material defgpencil_material;
 
 #ifdef __cplusplus
 }
diff --git a/source/blender/blenkernel/intern/gpencil.c b/source/blender/blenkernel/intern/gpencil.c
index d4bf76ea44a..456bc0c88f9 100644
--- a/source/blender/blenkernel/intern/gpencil.c
+++ b/source/blender/blenkernel/intern/gpencil.c
@@ -1161,38 +1161,34 @@ Material *BKE_gpencil_object_material_ensure_from_active_input_brush(Main *bmain
       brush->gpencil_settings->flag &= ~GP_BRUSH_MATERIAL_PINNED;
     }
   }
-  return BKE_gpencil_object_material_ensure_from_active_input_material(bmain, ob);
+  return BKE_gpencil_object_material_ensure_from_active_input_material(ob);
 }
 
 /**
  * Guaranteed to return a material assigned to object. Returns never NULL.
  * Only use this for materials unrelated to user input.
  */
-Material *BKE_gpencil_object_material_ensure_from_active_input_material(Main *bmain, Object *ob)
+Material *BKE_gpencil_object_material_ensure_from_active_input_material(Object *ob)
 {
   Material *ma = give_current_material(ob, ob->actcol);
   if (ma) {
     return ma;
   }
-  /* If the slot is empty, remove because will be added again,
-   * if not, we will get an empty slot. */
-  if ((ob->totcol > 0) && (ob->actcol == ob->totcol)) {
-    BKE_object_material_slot_remove(bmain, ob);
-  }
-  return BKE_gpencil_object_material_new(bmain, ob, "Material", NULL);
+
+  return &defgpencil_material;
 }
 
 /* Get active color, and add all default settings if we don't find anything */
-Material *BKE_gpencil_object_material_ensure_active(Main *bmain, Object *ob)
+Material *BKE_gpencil_object_material_ensure_active(Object *ob)
 {
   Material *ma = NULL;
 
   /* sanity checks */
-  if (ELEM(NULL, bmain, ob)) {
+  if (ob == NULL) {
     return NULL;
   }
 
-  ma = BKE_gpencil_object_material_ensure_from_active_input_material(bmain, ob);
+  ma = BKE_gpencil_object_material_ensure_from_active_input_material(ob);
   if (ma->gp_style == NULL) {
     BKE_material_init_gpencil_settings(ma);
   }
@@ -2008,6 +2004,7 @@ void BKE_gpencil_material_index_reassign(bGPdata *gpd, int totcol, int index)
         /* reassign strokes */
         if ((gps->mat_nr > index) || (gps->mat_nr > totcol - 1)) {
           gps->mat_nr--;
+          CLAMP_MIN(gps->mat_nr, 0);
         }
       }
     }
diff --git a/source/blender/blenkernel/intern/material.c b/source/blender/blenkernel/intern/material.c
index 1545ae4f48f..cc9be2c5dda 100644
--- a/source/blender/blenkernel/intern/material.c
+++ b/source/blender/blenkernel/intern/material.c
@@ -71,6 +71,7 @@
 
 /* used in UI and render */
 Material defmaterial;
+Material defgpencil_material;
 
 static CLG_LogRef LOG = {"bke.material"};
 
@@ -78,6 +79,13 @@ static CLG_LogRef LOG = {"bke.material"};
 void init_def_material(void)
 {
   BKE_material_init(&defmaterial);
+  BKE_material_gpencil_init(&defgpencil_material);
+}
+
+/* Free the GPencil data of the deafult material, creator.c */
+void BKE_material_gpencil_default_free(void)
+{
+  MEM_SAFE_FREE(defgpencil_material.gp_style);
 }
 
 /** Free (or release) any data used by this material (does not free the material itself). */
@@ -144,6 +152,16 @@ void BKE_material_init(Material *ma)
   ma->blend_shadow = MA_BS_SOLID;
 }
 
+void BKE_material_gpencil_init(Material *ma)
+{
+  BKE_material_init(ma);
+
+  /* grease pencil settings */
+  strcpy(ma->id.name, "MADefault GPencil");
+  BKE_material_init_gpencil_settings(ma);
+  add_v3_fl(&ma->gp_style->stroke_rgba[0], 0.6f);
+}
+
 Material *BKE_material_add(Main *bmain, const char *name)
 {
   Material *ma;
@@ -580,6 +598,17 @@ Material *give_current_material(Object *ob, short act)
   return ma_p ? *ma_p : NULL;
 }
 
+Material *BKE_material_gpencil_get(Object *ob, short act)
+{
+  Material *ma = give_current_material(ob, act);
+  if (ma != NULL) {
+    return ma;
+  }
+  else {
+    return &defgpencil_material;
+  }
+}
+
 MaterialGPencilStyle *BKE_material_gpencil_settings_get(Object *ob, short act)
 {
   Material *ma = give_current_material(ob, act);
@@ -591,7 +620,7 @@ MaterialGPencilStyle *BKE_material_gpencil_settings_get(Object *ob, short act)
     return ma->gp_style;
   }
   else {
-    return NULL;
+    return defgpencil_material.gp_style;
   }
 }
 
@@ -1070,10 +1099,6 @@ bool BKE_object_material_slot_remove(Main *bmain, Object *ob)
   }
   /* check indices from gpencil */
   else if (ob->type == OB_GPENCIL) {
-    /* need one color */
-    if (ob->totcol == 0) {
-      BKE_gpencil_object_material_ensure_from_active_input_material(bmain, ob);
-    }
     BKE_gpencil_material_index_reassign((bGPdata *)ob->data, ob->totcol, actcol - 1);
   }
 
diff --git a/source/blender/editors/gpencil/gpencil_add_monkey.c b/source/blender/editors/gpencil/gpencil_add_monkey.c
index c4528518009..139697ad0e3 100644
--- a/source/blender/editors/gpencil/gpencil_add_monkey.c
+++ b/source/blender/editors/gpencil/gpencil_add_monkey.c
@@ -54,7 +54,7 @@ static int gpencil_monkey_color(
   short *totcol = give_totcolp(ob);
   Material *ma = NULL;
   for (short i = 0; i < *totcol; i++) {
-    ma = give_current_material(ob, i + 1);
+    ma = BKE_material_gpencil_get(ob, i + 1);
     if (STREQ(ma->id.name, pct->name)) {
       return i;
     }
diff --git a/source/blender/editors/gpencil/gpencil_add_stroke.c b/source/blender/editors/gpencil/gpencil_add_stroke.c
index 80e239c9ae5..74617599eaa 100644
--- a/source/blender/editors/gpencil/gpencil_add_stroke.c
+++ b/source/blender/editors/gpencil/gpencil_add_stroke.c
@@ -53,7 +53,7 @@ static int gp_stroke_material(Main *bmain, Object *ob, const ColorTemplate *pct,
   short *totcol = give_totcolp(ob);
   Material *ma = NULL;
   for (short i = 0; i < *totcol; i++) {
-    ma = give_current_material(ob, i + 1);
+    ma = BKE_material_gpencil_get(ob, i + 1);
     if (STREQ(ma->id.name, pct->name)) {
       return i;
     }
diff --git a/source/blender/editors/gpencil/gpencil_data.c b/source/blender/editors/gpencil/gpencil_data.c
index 34beceddfa2..e763eec1b0d 100644
--- a/source/blender/editors/gpencil/gpencil_data.c
+++ b/source/blender/editors/gpencil/gpencil_data.c
@@ -538,10 +538,12 @@ static int gp_layer_duplicate_object_exec(bContext *C, wmOperator *op)
        * otherwise add the slot with the material
        */
       Material *ma_src = give_current_material(ob_src, gps_src->mat_nr + 1);
-      int idx = BKE_gpencil_object_material_ensure(bmain, ob_dst, ma_src);
+      if (ma_src != NULL) {
+        int idx = BKE_gpencil_object_material_ensure(bmain, ob_dst, ma_src);
 
-      /* Reassign the stroke material to the right slot in destination object. */
-      gps_dst->mat_nr = idx;
+        /* Reassign the stroke material to the right slot in destination object. */
+        gps_dst->mat_nr = idx;
+      }
 
       /* add new stroke to frame */
       BLI_addtail(&gpf_dst->strokes, gps_dst);
@@ -1423,7 +1425,7 @@ static int gp_stroke_change_color_exec(bContext *C, wmOperator *op)
   bGPdata *gpd = ED_gpencil_data_get_active(C);
   Object *ob = CTX_data_active_object(C);
   if (name[0] == '\0') {
-    ma = give_current_material(ob, ob->actcol);
+    ma = BKE_material_gpencil_get(ob, ob->actcol);
   }
   else {
     ma = (Material *)BKE_libblock_find_name(bmain, ID_MA, name);
@@ -1543,9 +1545,10 @@ static int gp_stroke_lock_color_exec(bContext *C, wmOperator *UNUSED(op))
           }
           /* unlock color */
           Material *tmp_ma = give_current_material(ob, gps->mat_nr + 1);
-
-          tmp_ma->gp_style->flag &= ~GP_STYLE_COLOR_LOCKED;
-          DEG_id_tag_update(&tmp_ma->id, ID_RECALC_COPY_ON_WRITE);
+          if (tmp_ma) {
+            tmp_ma->gp_style->flag &= ~GP_STYLE_COLOR_LOCKED;
+            DEG_id_tag_update(&tmp_ma->id, ID_RECALC_COPY_ON_WRITE);
+          }
         }
       }
     }
@@ -2295,7 +2298,7 @@ int ED_gpencil_join_objects_exec(bContext *C, wmOperator *op)
         short *totcol = give_totcolp(ob_src);
 
         for (short i = 0; i < *totcol; i++) {
-          Material *tmp_ma = give_current_material(ob_src, i + 1);
+          Material *tmp_ma = BKE_material_gpencil_get(ob_src, i + 1);
           BKE_gpencil_object_material_ensure(bmain, ob_dst, tmp_ma);
         }
 
@@ -2329,7 +2332,7 @@ int ED_gpencil_join_objects_exec(bContext *C, wmOperator *op)
             for (bGPDstroke *gps = gpf->strokes.first; gps; gps = gps->next) {
 
               /* Reassign material. Look old material and try to find in destination. */
-              ma_src = give_current_material(ob_src, gps->mat_nr + 1);
+              ma_src = BKE_material_gpencil_get(ob_src, gps->mat_nr + 1);
               gps->mat_nr = BKE_gpencil_object_material_ensure(bmain, ob_dst, ma_src);
 
               bGPDspoint *pt;
@@ -2437,7 +2440,7 @@ static int gpencil_lock_layer_exec(bContext *C, wmOperator *UNUSED(op))
   }
 
   for (short i = 0; i < *totcol; i++) {
-    ma = give_current_material(ob, i + 1);
+    ma = BKE_material_gpencil_get(ob, i + 1);
     if (ma) {
       gp_style = ma->gp_style;
       gp_style->flag |= GP_STYLE_COLOR_LOCKED;
@@ -2457,7 +2460,7 @@ static int gpencil_lock_layer_exec(bContext *C, wmOperator *UNUSED(op))
           continue;
         }
 
-        ma = give_current_material(ob, gps->mat_nr + 1);
+        ma = BKE_material_gpencil_get(ob, gps->mat_nr + 1);
         DEG_id_tag_update(&ma->id, ID_RECALC_COPY_ON_WRITE);
 
         gp_style = ma->gp_style;
@@ -2500,7 +2503,7 @@ static int gpencil_color_isolate_exec(bContext *C, wmOperator *op)
 {
   bGPdata *gpd = ED_gpencil_data_get_active(C);
   Object *ob = CTX_data_active_object(C);
-  Material *active_ma = give_current_material(ob, ob->actcol);
+  Material *active_ma = BKE_material_gpencil_get(ob, ob->actcol);
   MaterialGPencilStyle *active_color = BKE_material_gpencil_settings_get(ob, ob->actcol);
   MaterialGPencilStyle *gp_style;
 
@@ -2520,7 +2523,7 @@ static int gpencil_color_isolate_exec(bContext *C, wmOperator *op)
   Material *ma = NULL;
   short *totcol = give_totcolp(ob);
   for (short i = 0; i < *totcol; i++) {
-    ma = give_current_material(ob, i + 1);
+    ma = BKE_material_gpencil_get(ob, i + 1);
     /* Skip if this is the active one */
     if ((ma == NULL) || (ma == active_ma)) {
       continue;
@@ -2540,7 +2543,7 @@ static int gpencil_color_isolate_exec(bContext *C, wmOperator *op)
   if (isolate) {
     /* Set flags on all "other" colors */
     for (short i = 0; i < *totcol; i++) {
-      ma = give_current_material(ob, i + 1);
+      ma = BKE_material_gpencil_get(ob, i + 1);
       if (ma == NULL) {
         continue;
       }
@@ -2557,7 +2560,7 @@ static int gpencil_color_isolate_exec(bContext *C, wmOperator *op)
   else {
     /* Clear flags - Restore everything else */
     for (short i = 0; i < *totcol; i++) {
-      ma = give_current_material(ob, i + 1);
+      ma = BKE_material_gpencil_get(ob, i + 1);
       if (ma == NULL) {
         continue;
       }
@@ -2622,7 +2625,7 @@ static int gpencil_color_hide_exec(bContext *C, wmOperator *op)
     /* hide unselected */
     MaterialGPencilStyle *color = NULL;
     for (short i = 0; i < *totcol; i++) {
-      ma = give_current_material(ob, i + 1);
+      ma = BKE_material_gpencil_get(ob, i + 1);
       if (ma) {
         color = ma->gp_style;
         if (active_color != color) {
@@ -2685,7 +2688,7 @@ static int gpencil_color_reveal_exec(bContext *C, wmOperator *UNUSED(op))
   MaterialGPencilStyle *gp_style = NULL;
 
   for (short i = 0; i < *totcol; i++) {
-    ma = give_current_material(ob, i + 1);
+    ma = BKE_material_gpencil_get(ob, i + 1);
     if (ma) {
       gp_style = ma->gp_style;
       gp_style->flag &= ~GP_STYLE_COLOR_HIDE;
@@ -2738,7 +2741,7 @@ static int gpencil_color_lock_all_exec(bContext *C, wmOperator *UNUSED(op))
   MaterialGPencilStyle *gp_style = NULL;
 
   for (short i = 0; i < *totcol; i++) {
-    ma = give_current_material(ob, i + 1);
+    ma = BKE_material_gpencil_get(ob, i + 1);
     if (ma) {
       gp_style = ma->gp_style;
       gp_style->flag |= GP_STYLE_COLOR_LOCKED;
@@ -2791,7 +2794,7 @@ static int gpencil_color_unlock_all_exec(bContext *C, wmOperator *UNUSED(op))
   MaterialGPencilStyle *gp_style = NULL;
 
   for (short i = 0; i < *totcol; i++) {
-    ma = give_current_material(ob, i + 1);
+    ma = BKE_material_gpencil_get(ob, i + 1);
     if (ma) {
       gp_style = ma->gp_style;
       gp_style->flag &= ~GP_STYLE_COLOR_LOCKED;
diff --git a/source/blender/editors/gpencil/gpencil_edit.c b/source/blender/editors/gpencil/gpencil_edit.c
index 709374fa519..8442c906ac1 100644
--- a/source/blender/editors/gpencil/gpencil_edit.c
+++ b/source/blender/editors/gpencil/gpencil_edit.c
@@ -1191,10 +1191,15 @@ static int gp_strokes_copy_exec(bContext *C, wmOperator *op)
     GHash *ma_to_name = gp_strokes_copypastebuf_colors_material_to_name_create(bmain);
     for (bGPDstroke *gps = gp_strokes_copypastebuf.first; gps; gps = gps->next) {
       if (ED_gpencil_stroke_can_use(C, gps)) {
+        Material *ma = give_current_material(ob, gps->mat_nr + 1);
+        /* Avoid default material. */
+        if (ma == NULL) {
+          continue;
+        }
+
         char **ma_name_val;
         if (!BLI_ghash_ensure_p(
                 gp_strokes_copypastebuf_colors, &gps->mat_nr, (void ***)&ma_name_val)) {
-          Material *ma = give_current_material(ob, gps->mat_nr + 1);
           char *ma_name = BLI_ghash_lookup(ma_to_name, ma);
           *ma_name_val = MEM_dupallocN(ma_name);
         }
@@ -1361,7 +1366,7 @@ static int gp_strokes_paste_exec(bContext *C, wmOperator *op)
         /* Remap material */
         Material *ma = BLI_ghash_lookup(new_colors, POINTER_FROM_INT(new_stroke->mat_nr));
         new_stroke->mat_nr = BKE_gpencil_object_material_get_index(ob, ma);
-        BLI_assert(new_stroke->mat_nr >= 0); /* have to add the material first */
+        CLAMP_MIN(new_stroke->mat_nr, 0);
       }
     }
   }
@@ -4068,7 +4073,7 @@ static int gp_stroke_separate_exec(bContext *C, wmOperator *op)
               /* add duplicate materials */
 
               /* XXX same material can be in multiple slots. */
-              ma = give_current_material(ob, gps->mat_nr + 1);
+              ma = BKE_material_gpencil_get(ob, gps->mat_nr + 1);
 
               idx = BKE_gpencil_object_material_ensure(bmain, ob_dst, ma);
 
@@ -4141,7 +4146,7 @@ static int gp_stroke_separate_exec(bContext *C, wmOperator *op)
           if (ED_gpencil_stroke_can_use(C, gps) == false) {
             continue;
           }
-          ma = give_current_material(ob, gps->mat_nr + 1);
+          ma = BKE_material_gpencil_get(ob, gps->mat_nr + 1);
           gps->mat_nr = BKE_gpencil_object_material_ensure(bmain, ob_dst, ma);
         }
       }
diff --git a/source/blender/editors/gpencil/gpencil_fill.c b/source/blender/editors/gpencil/gpencil_fill.c
index 5637e755198..372973e1040 100644
--- a/source/blender/editors/gpencil/gpencil_fill.c
+++ b/source/blender/editors/gpencil/gpencil_fill.c
@@ -48,6 +48,7 @@
 #include "BKE_context.h"
 #include "BKE_screen.h"
 #include "BKE_paint.h"
+#include "BKE_report.h"
 
 #include "ED_gpencil.h"
 #include "ED_screen.h"
@@ -1038,7 +1039,15 @@ static void gpencil_stroke_from_buffer(tGPDfill *tgpf)
   gps->flag |= GP_STROKE_CYCLIC;
   gps->flag |= GP_STROKE_3DSPACE;
 
-  gps->mat_nr = BKE_gpencil_object_material_ensure(tgpf->bmain, tgpf->ob, tgpf->mat);
+  gps->mat_nr = BKE_gpencil_object_material_get_index_from_brush(tgpf->ob, brush);
+  if (gps->mat_nr < 0) {
+    if (tgpf->ob->actcol - 1 < 0) {
+      gps->mat_nr = 0;
+    }
+    else {
+      gps->mat_nr = tgpf->ob->actcol - 1;
+    }
+  }
 
   /* allocate memory for storage points */
   gps->totpoints = tgpf->sbuffer_used;
@@ -1346,8 +1355,28 @@ static int gpencil_fill_init(bContext *C, wmOperator *op)
 /* start of interactive part of operator */
 static int gpencil_fill_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(event))
 {
+  Object *ob = CTX_data_active_object(C);
+  ToolSettings *ts = CTX_data_tool_settings(C);
+  Brush *brush = BKE_paint_brush(&ts->gp_paint->paint);
   tGPDfill *tgpf = NULL;
 
+  /* Fill tool needs a material (cannot use default material) */
+  bool valid = true;
+  if ((brush) && (brush->gpencil_settings->flag & GP_BRUSH_MATERIAL_PINNED)) {
+    if (brush->gpencil_settings->material == NULL) {
+      valid = false;
+    }
+  }
+  else {
+    if (give_current_material(ob, ob->actcol) == NULL) {
+      valid = false;
+    }
+  }
+  if (!valid) {
+    BKE_report(op->reports, RPT_ERROR, "Fill tool needs active material.");
+    return OPERATOR_CANCELLED;
+  }
+
   /* try to initialize context data needed */
   if (!gpencil_fill_init(C, op)) {
     gpencil_fill_exit(C, op);
diff --git a/source/blender/editors/gpencil/gpencil_merge.c b/source/blender/editors/gpencil/gpencil_merge.c
index cb11bb4cd63..930911ffac5 100644
--- a/source/blender/editors/gpencil/gpencil_merge.c
+++ b/source/blender/editors/gpencil/gpencil_merge.c
@@ -449,7 +449,7 @@ static bool gp_strokes_merge_poll(bContext *C)
 
   /* check material */
   Material *ma = NULL;
-  ma = give_current_material(ob, ob->actcol);
+  ma = BKE_material_gpencil_get(ob, ob->actcol);
   if ((ma == NULL) || (ma->gp_style == NULL)) {
     return false;
   }
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);
diff --git a/source/blender/editors/gpencil/gpencil_primitive.c b/source/blender/editors/gpencil/gpencil_primitive.c
index e4b2e5540ea..8d4c75d2e8c 100644
--- a/source/blender/editors/gpencil/gpencil_primitive.c
+++ b/source/blender/editors/gpencil/gpencil_primitive.c
@@ -330,7 +330,15 @@ static void gp_primitive_set_initdata(bContext *C, tGPDprimitive *tgpi)
 
   gps->flag |= GP_STROKE_3DSPACE;
 
-  gps->mat_nr = BKE_gpencil_object_material_get_index(tgpi->ob, tgpi->mat);
+  gps->mat_nr = BKE_gpencil_object_material_get_index_from_brush(tgpi->ob, tgpi->brush);
+  if (gps->mat_nr < 0) {
+    if (tgpi->ob->actcol - 1 < 0) {
+      gps->mat_nr = 0;
+    }
+    else {
+      gps->mat_nr = tgpi->ob->actcol - 1;
+    }
+  }
 
   /* allocate memory for storage points, but keep empty */
   gps->totpoints = 0;
diff --git a/source/blender/editors/gpencil/gpencil_utils.c b/source/blender/editors/gpencil/gpencil_utils.c
index 25b4036b8b1..d7492b5be4d 100644
--- a/source/blender/editors/gpencil/gpencil_utils.c
+++ b/source/blender/editors/gpencil/gpencil_utils.c
@@ -2064,7 +2064,7 @@ void ED_gpencil_update_color_uv(Main *bmain, Material *mat)
               if (ED_gpencil_stroke_color_use(ob, gpl, gps) == false) {
                 continue;
               }
-              gps_ma = give_current_material(ob, gps->mat_nr + 1);
+              gps_ma = BKE_material_gpencil_get(ob, gps->mat_nr + 1);
               /* update */
               if ((gps_ma) && (gps_ma == mat)) {
                 ED_gpencil_calc_stroke_uv(ob, gps);
diff --git a/source/blender/windowmanager/intern/wm_init_exit.c b/source/blender/windowmanager/intern/wm_init_exit.c
index 29cb02888ac..d08f4e236ee 100644
--- a/source/blender/windowmanager/intern/wm_init_exit.c
+++ b/source/blender/windowmanager/intern/wm_init_exit.c
@@ -524,6 +524,7 @@ void WM_exit_ex(bContext *C, const bool do_python)
 
   BKE_addon_pref_type_free();
   BKE_keyconfig_pref_type_free();
+  BKE_material_gpencil_default_free();
 
   wm_operatortype_free();
   wm_dropbox_free();