GPencil: Only brushes with pinned materials have materials

Using GP_BRUSH_MATERIAL_PINNED to switch between active material and brush material, instead of updating all brushes on active material changes. This will allow brushes to have no material and therefore to not inflate the user count.

This fix T62465.

Patch contributed by @matc
Reviewers: @brecht @antoniov @billreynish @mendio

5 files changed, 150 insertions, 32 deletions

diff --git a/source/blender/blenkernel/BKE_brush.h b/source/blender/blenkernel/BKE_brush.h
index 9360962317c..30746af0b53 100644
--- a/source/blender/blenkernel/BKE_brush.h
+++ b/source/blender/blenkernel/BKE_brush.h
@@ -56,7 +56,6 @@ void BKE_brush_free(struct Brush *brush);
 
 void BKE_brush_sculpt_reset(struct Brush *brush);
 void BKE_brush_gpencil_presets(struct bContext *C);
-void BKE_brush_update_material(struct Main *bmain, struct Material *ma, struct Brush *exclude_brush);
 
 /* image icon function */
 struct ImBuf *get_brush_icon(struct Brush *brush);
diff --git a/source/blender/blenkernel/BKE_gpencil.h b/source/blender/blenkernel/BKE_gpencil.h
index 353ba61b70d..e94ba27a8ea 100644
--- a/source/blender/blenkernel/BKE_gpencil.h
+++ b/source/blender/blenkernel/BKE_gpencil.h
@@ -132,6 +132,21 @@ void BKE_gpencil_layer_setactive(struct bGPdata *gpd, struct bGPDlayer *active);
 void BKE_gpencil_layer_delete(struct bGPdata *gpd, struct bGPDlayer *gpl);
 
 struct Material *BKE_gpencil_get_material_from_brush(struct Brush *brush);
+void BKE_gpencil_brush_set_material(struct Brush *brush, struct Material *material);
+
+struct Material *BKE_gpencil_handle_brush_material(struct Main *bmain, struct Object *ob, struct Brush *brush);
+int BKE_gpencil_handle_material(struct Main *bmain, struct Object *ob, struct Material *material);
+
+struct Material *BKE_gpencil_handle_new_material(struct Main *bmain, struct Object *ob, const char *name, int *r_index);
+
+struct Material *BKE_gpencil_get_material_for_brush(struct Object *ob, struct Brush *brush);
+int BKE_gpencil_get_material_index_for_brush(struct Object *ob, struct Brush *brush);
+
+struct Material *BKE_gpencil_current_input_toolsettings_material(struct Main *bmain, struct Object *ob, struct ToolSettings *ts);
+struct Material *BKE_gpencil_current_input_brush_material(struct Main *bmain, struct Object *ob, struct Brush *brush);
+struct Material *BKE_gpencil_current_input_material(struct Main *bmain, struct Object *ob);
+
+
 struct Material *BKE_gpencil_material_ensure(struct Main *bmain, struct Object *ob);
 
 /* object boundbox */
diff --git a/source/blender/blenkernel/intern/brush.c b/source/blender/blenkernel/intern/brush.c
index c959504f84f..ea5605d8ed1 100644
--- a/source/blender/blenkernel/intern/brush.c
+++ b/source/blender/blenkernel/intern/brush.c
@@ -540,24 +540,6 @@ void BKE_brush_gpencil_presets(bContext *C)
 
 }
 
-void BKE_brush_update_material(Main *bmain, Material *ma, Brush *exclude_brush)
-{
-	for (Brush *brush = bmain->brushes.first; brush; brush = brush->id.next) {
-		if ((exclude_brush != NULL) && (brush == exclude_brush)) {
-			continue;
-		}
-
-		if (brush->gpencil_settings != NULL) {
-			BrushGpencilSettings *gpencil_settings = brush->gpencil_settings;
-			if (((gpencil_settings->flag & GP_BRUSH_MATERIAL_PINNED) == 0) &&
-			    (gpencil_settings->material != ma))
-			{
-				gpencil_settings->material = ma;
-			}
-		}
-	}
-}
-
 struct Brush *BKE_brush_first_search(struct Main *bmain, const eObjectMode ob_mode)
 {
 	Brush *brush;
diff --git a/source/blender/blenkernel/intern/gpencil.c b/source/blender/blenkernel/intern/gpencil.c
index eb6fc9ceeeb..263bf4e57e2 100644
--- a/source/blender/blenkernel/intern/gpencil.c
+++ b/source/blender/blenkernel/intern/gpencil.c
@@ -996,6 +996,136 @@ Material *BKE_gpencil_get_material_from_brush(Brush *brush)
 	return ma;
 }
 
+void BKE_gpencil_brush_set_material(Brush *brush, Material *ma)
+{
+	BLI_assert(brush);
+	BLI_assert(brush->gpencil_settings);
+	if (brush->gpencil_settings->material != ma) {
+		if (brush->gpencil_settings->material) {
+			id_us_min(&brush->gpencil_settings->material->id);
+		}
+		if (ma) {
+			id_us_plus(&ma->id);
+		}
+		brush->gpencil_settings->material = ma;
+	}
+}
+
+/* Adds the pinned material to the object if necessary. */
+Material *BKE_gpencil_handle_brush_material(Main *bmain, Object *ob, Brush *brush)
+{
+	if (brush->gpencil_settings->flag & GP_BRUSH_MATERIAL_PINNED) {
+		Material *ma = BKE_gpencil_get_material_from_brush(brush);
+
+		/* check if the material is already on object material slots and add it if missing */
+		if (ma && BKE_gpencil_get_material_index(ob, ma) < 0) {
+			BKE_object_material_slot_add(bmain, ob);
+			assign_material(bmain, ob, ma, ob->totcol, BKE_MAT_ASSIGN_USERPREF);
+		}
+
+		return ma;
+	}
+	else {
+		/* using active material instead */
+		return give_current_material(ob, ob->actcol);
+	}
+}
+
+/* Assigns the material to object (if not already present) and returns its index (mat_nr). */
+int BKE_gpencil_handle_material(Main *bmain, Object *ob, Material *material)
+{
+	if (!material) {
+		return -1;
+	}
+	int index = BKE_gpencil_get_material_index(ob, material);
+	if (index < 0) {
+		BKE_object_material_slot_add(bmain, ob);
+		assign_material(bmain, ob, material, ob->totcol, BKE_MAT_ASSIGN_USERPREF);
+		return ob->totcol - 1;
+	}
+	return index;
+}
+
+/** Creates a new gpencil material and assigns it to object.
+ *
+ * \param *r_index: value is set to zero based index of the new material if r_index is not NULL
+ */
+Material *BKE_gpencil_handle_new_material(Main *bmain, Object *ob, const char *name, int *r_index)
+{
+	Material *ma = BKE_material_add_gpencil(bmain, name);
+	id_us_min(&ma->id); /* no users yet */
+
+	BKE_object_material_slot_add(bmain, ob);
+	assign_material(bmain, ob, ma, ob->totcol, BKE_MAT_ASSIGN_USERPREF);
+
+	if (r_index) {
+		*r_index = ob->actcol - 1;
+	}
+	return ma;
+}
+
+/* Returns the material for a brush with respect to its pinned state. */
+Material *BKE_gpencil_get_material_for_brush(Object *ob, Brush *brush)
+{
+	if (brush->gpencil_settings->flag & GP_BRUSH_MATERIAL_PINNED) {
+		Material *ma = BKE_gpencil_get_material_from_brush(brush);
+		return ma;
+	}
+	else {
+		return give_current_material(ob, ob->actcol);
+	}
+}
+
+/* Returns the material index for a brush with respect to its pinned state. */
+int BKE_gpencil_get_material_index_for_brush(Object *ob, Brush *brush)
+{
+	if (brush->gpencil_settings->flag & GP_BRUSH_MATERIAL_PINNED) {
+		return BKE_gpencil_get_material_index(ob, brush->gpencil_settings->material);
+	}
+	else {
+		return ob->actcol - 1;
+	}
+}
+
+/* Guaranteed to return a material assigned to object. Returns never NULL. */
+Material *BKE_gpencil_current_input_toolsettings_material(Main *bmain, Object *ob, ToolSettings *ts)
+{
+	if (ts && ts->gp_paint && ts->gp_paint->paint.brush) {
+		return BKE_gpencil_current_input_brush_material(bmain, ob, ts->gp_paint->paint.brush);
+	}
+	else {
+		return BKE_gpencil_current_input_brush_material(bmain, ob, NULL);
+	}
+}
+
+/* Guaranteed to return a material assigned to object. Returns never NULL. */
+Material *BKE_gpencil_current_input_brush_material(Main *bmain, Object *ob, Brush *brush)
+{
+	Material *ma;
+	if (brush) {
+		ma = BKE_gpencil_handle_brush_material(bmain, ob, brush);
+		if (!ma && brush->gpencil_settings->flag & GP_BRUSH_MATERIAL_PINNED) {
+			/* it is easier to just unpin a NULL material, instead of setting a new one */
+			brush->gpencil_settings->flag &= ~GP_BRUSH_MATERIAL_PINNED;
+		}
+	}
+	if (ma) {
+		return ma;
+	}
+	return BKE_gpencil_current_input_material(bmain, ob);
+}
+
+/* Guaranteed to return a material assigned to object. Returns never NULL. Only use this for materials unrelated to user input */
+Material *BKE_gpencil_current_input_material(Main *bmain, Object *ob)
+{
+	Material *ma;
+	ma = give_current_material(ob, ob->actcol);
+	if (ma) {
+		return ma;
+	}
+	return BKE_gpencil_handle_new_material(bmain, ob, "Material", NULL);
+}
+
 /* Get active color, and add all default settings if we don't find anything */
 Material *BKE_gpencil_material_ensure(Main *bmain, Object *ob)
 {
@@ -1005,15 +1135,8 @@ Material *BKE_gpencil_material_ensure(Main *bmain, Object *ob)
 	if (ELEM(NULL, bmain, ob))
 		return NULL;
 
-	ma = give_current_material(ob, ob->actcol);
-	if (ma == NULL) {
-		if (ob->totcol == 0) {
-			BKE_object_material_slot_add(bmain, ob);
-		}
-		ma = BKE_material_add_gpencil(bmain, DATA_("Material"));
-		assign_material(bmain, ob, ma, ob->totcol, BKE_MAT_ASSIGN_USERPREF);
-	}
-	else if (ma->gp_style == NULL) {
+	ma = BKE_gpencil_current_input_material(bmain, ob);
+	if (ma->gp_style == NULL) {
 		BKE_material_init_gpencil_settings(ma);
 	}
 
@@ -1538,7 +1661,7 @@ void BKE_gpencil_stats_update(bGPdata *gpd)
 
 }
 
-/* get material index */
+/* get material index (0-based like mat_nr not actcol) */
 int BKE_gpencil_get_material_index(Object *ob, Material *ma)
 {
 	short *totcol = give_totcolp(ob);
@@ -1546,11 +1669,11 @@ int BKE_gpencil_get_material_index(Object *ob, Material *ma)
 	for (short i = 0; i < *totcol; i++) {
 		read_ma = give_current_material(ob, i + 1);
 		if (ma == read_ma) {
-			return i + 1;
+			return i;
 		}
 	}
 
-	return 0;
+	return -1;
 }
 
 /* Get points of stroke always flat to view not affected by camera view or view position */
diff --git a/source/blender/blenkernel/intern/material.c b/source/blender/blenkernel/intern/material.c
index 88a96ff098e..f708984e51f 100644
--- a/source/blender/blenkernel/intern/material.c
+++ b/source/blender/blenkernel/intern/material.c
@@ -164,7 +164,6 @@ Material *BKE_material_add_gpencil(Main *bmain, const char *name)
 	/* grease pencil settings */
 	if (ma != NULL) {
 		BKE_material_init_gpencil_settings(ma);
-		BKE_brush_update_material(bmain, ma, NULL);
 	}
 	return ma;
 }