UV/VCol layers creation: add option to not init those new data.

`ED_mesh_uv_texture_add()`/`ED_mesh_color_add()` would always either
copy data from current active one, or (for UVs), generate default
'valid' UVs for every face.

This commit adds an option to not do that, just keeping default values
from raw CDLayer creation. It is only used/exposed from RNA API
currently.

This is especially useful for importer add-ons, since some formats
support multiple layers of those kind, as well as 'partial' dataset not
explicitely defining values for all mesh items.

Preliminary step to fix T62224.

1 files changed, 11 insertions, 11 deletions

diff --git a/source/blender/editors/mesh/mesh_data.c b/source/blender/editors/mesh/mesh_data.c
index a1c2f5e0121..ea64adbffa3 100644
--- a/source/blender/editors/mesh/mesh_data.c
+++ b/source/blender/editors/mesh/mesh_data.c
@@ -250,7 +250,7 @@ void ED_mesh_uv_loop_reset(struct bContext *C, struct Mesh *me)
 }
 
 /* note: keep in sync with ED_mesh_color_add */
-int ED_mesh_uv_texture_add(Mesh *me, const char *name, const bool active_set)
+int ED_mesh_uv_texture_add(Mesh *me, const char *name, const bool active_set, const bool do_init)
 {
 	BMEditMesh *em;
 	int layernum_dst;
@@ -267,7 +267,7 @@ int ED_mesh_uv_texture_add(Mesh *me, const char *name, const bool active_set)
 		/* CD_MLOOPUV */
 		BM_data_layer_add_named(em->bm, &em->bm->ldata, CD_MLOOPUV, name);
 		/* copy data from active UV */
-		if (layernum_dst) {
+		if (layernum_dst && do_init) {
 			const int layernum_src = CustomData_get_active_layer(&em->bm->ldata, CD_MLOOPUV);
 			BM_data_layer_copy(em->bm, &em->bm->ldata, CD_MLOOPUV, layernum_src, layernum_dst);
 
@@ -282,7 +282,7 @@ int ED_mesh_uv_texture_add(Mesh *me, const char *name, const bool active_set)
 		if (layernum_dst >= MAX_MTFACE)
 			return -1;
 
-		if (me->mloopuv) {
+		if (me->mloopuv && do_init) {
 			CustomData_add_layer_named(&me->ldata, CD_MLOOPUV, CD_DUPLICATE, me->mloopuv, me->totloop, name);
 			CustomData_add_layer_named(&me->fdata, CD_MTFACE, CD_DUPLICATE, me->mtface, me->totface, name);
 			is_init = true;
@@ -301,7 +301,7 @@ int ED_mesh_uv_texture_add(Mesh *me, const char *name, const bool active_set)
 	}
 
 	/* don't overwrite our copied coords */
-	if (is_init == false) {
+	if (!is_init && do_init) {
 		ED_mesh_uv_loop_reset_ex(me, layernum_dst);
 	}
 
@@ -321,12 +321,12 @@ void ED_mesh_uv_texture_ensure(struct Mesh *me, const char *name)
 
 		layernum_dst = CustomData_number_of_layers(&em->bm->ldata, CD_MLOOPUV);
 		if (layernum_dst == 0)
-			ED_mesh_uv_texture_add(me, name, true);
+			ED_mesh_uv_texture_add(me, name, true, true);
 	}
 	else {
 		layernum_dst = CustomData_number_of_layers(&me->ldata, CD_MLOOPUV);
 		if (layernum_dst == 0)
-			ED_mesh_uv_texture_add(me, name, true);
+			ED_mesh_uv_texture_add(me, name, true, true);
 	}
 }
 
@@ -377,7 +377,7 @@ bool ED_mesh_uv_texture_remove_named(Mesh *me, const char *name)
 }
 
 /* note: keep in sync with ED_mesh_uv_texture_add */
-int ED_mesh_color_add(Mesh *me, const char *name, const bool active_set)
+int ED_mesh_color_add(Mesh *me, const char *name, const bool active_set, const bool do_init)
 {
 	BMEditMesh *em;
 	int layernum;
@@ -393,7 +393,7 @@ int ED_mesh_color_add(Mesh *me, const char *name, const bool active_set)
 		/* CD_MLOOPCOL */
 		BM_data_layer_add_named(em->bm, &em->bm->ldata, CD_MLOOPCOL, name);
 		/* copy data from active vertex color layer */
-		if (layernum) {
+		if (layernum && do_init) {
 			const int layernum_dst = CustomData_get_active_layer(&em->bm->ldata, CD_MLOOPCOL);
 			BM_data_layer_copy(em->bm, &em->bm->ldata, CD_MLOOPCOL, layernum_dst, layernum);
 		}
@@ -407,7 +407,7 @@ int ED_mesh_color_add(Mesh *me, const char *name, const bool active_set)
 			return -1;
 		}
 
-		if (me->mloopcol) {
+		if (me->mloopcol && do_init) {
 			CustomData_add_layer_named(&me->ldata, CD_MLOOPCOL, CD_DUPLICATE, me->mloopcol, me->totloop, name);
 			CustomData_add_layer_named(&me->fdata, CD_MCOL, CD_DUPLICATE, me->mcol, me->totface, name);
 		}
@@ -499,7 +499,7 @@ static int mesh_uv_texture_add_exec(bContext *C, wmOperator *UNUSED(op))
 	Object *ob = ED_object_context(C);
 	Mesh *me = ob->data;
 
-	if (ED_mesh_uv_texture_add(me, NULL, true) == -1)
+	if (ED_mesh_uv_texture_add(me, NULL, true, true) == -1)
 		return OPERATOR_CANCELLED;
 
 	if (ob->mode & OB_MODE_TEXTURE_PAINT) {
@@ -565,7 +565,7 @@ static int mesh_vertex_color_add_exec(bContext *C, wmOperator *UNUSED(op))
 	Object *ob = ED_object_context(C);
 	Mesh *me = ob->data;
 
-	if (ED_mesh_color_add(me, NULL, true) == -1)
+	if (ED_mesh_color_add(me, NULL, true, true) == -1)
 		return OPERATOR_CANCELLED;
 
 	return OPERATOR_FINISHED;