Fix #31725: UV map order is ignored when opening in 2.6+ versions

Issue was caused by do_versions being used pdata as reference for active/render/
stencil/clone layer indices instead of fdata.

Added some utility functions used only by do_versions to be sure this indices
are set from fdata for pre-bmesh files.

5 files changed, 67 insertions, 1 deletions

diff --git a/source/blender/blenkernel/BKE_customdata.h b/source/blender/blenkernel/BKE_customdata.h
index bbe68db8bfe..3dc68edf12b 100644
--- a/source/blender/blenkernel/BKE_customdata.h
+++ b/source/blender/blenkernel/BKE_customdata.h
@@ -321,6 +321,7 @@ void CustomData_to_bmeshpoly(struct CustomData *fdata, struct CustomData *pdata,
                              struct CustomData *ldata, int totloop, int totpoly);
 void CustomData_from_bmeshpoly(struct CustomData *fdata, struct CustomData *pdata, struct CustomData *ldata, int total);
 void CustomData_bmesh_update_active_layers(struct CustomData *fdata, struct CustomData *pdata, struct CustomData *ldata);
+void CustomData_bmesh_do_versions_update_active_layers(struct CustomData *fdata, struct CustomData *pdata, struct CustomData *ldata);
 void CustomData_bmesh_init_pool(struct CustomData *data, int totelem, const char htype);
 
 /* External file storage */
diff --git a/source/blender/blenkernel/BKE_mesh.h b/source/blender/blenkernel/BKE_mesh.h
index 1878e43f577..887340622ad 100644
--- a/source/blender/blenkernel/BKE_mesh.h
+++ b/source/blender/blenkernel/BKE_mesh.h
@@ -151,6 +151,7 @@ void copy_dverts(struct MDeformVert *dst, struct MDeformVert *src, int totvert);
 void BKE_mesh_delete_material_index(struct Mesh *me, short index);
 void BKE_mesh_smooth_flag_set(struct Object *meshOb, int enableSmooth);
 void BKE_mesh_convert_mfaces_to_mpolys(struct Mesh *mesh);
+void BKE_mesh_do_versions_convert_mfaces_to_mpolys(struct Mesh *mesh);
 void BKE_mesh_convert_mfaces_to_mpolys_ex(struct ID *id,
                                           struct CustomData *fdata, struct CustomData *ldata, struct CustomData *pdata,
                                           int totedge_i, int totface_i, int totloop_i, int totpoly_i,
diff --git a/source/blender/blenkernel/intern/customdata.c b/source/blender/blenkernel/intern/customdata.c
index 5dc50dca45a..f551b2d18a4 100644
--- a/source/blender/blenkernel/intern/customdata.c
+++ b/source/blender/blenkernel/intern/customdata.c
@@ -2219,6 +2219,48 @@ void CustomData_bmesh_update_active_layers(CustomData *fdata, CustomData *pdata,
 	}
 }
 
+/* update active indices for active/render/clone/stencil custom data layers
+ * based on indices from fdata layers
+ * used by do_versions in readfile.c when creating pdata and ldata for pre-bmesh
+ * meshes and needed to preserve active/render/clone/stencil flags set in pre-bmesh files
+ */
+void CustomData_bmesh_do_versions_update_active_layers(CustomData *fdata, CustomData *pdata, CustomData *ldata)
+{
+	int act;
+
+	if (CustomData_has_layer(fdata, CD_MTFACE)) {
+		act = CustomData_get_active_layer(fdata, CD_MTFACE);
+		CustomData_set_layer_active(pdata, CD_MTEXPOLY, act);
+		CustomData_set_layer_active(ldata, CD_MLOOPUV, act);
+
+		act = CustomData_get_render_layer(fdata, CD_MTFACE);
+		CustomData_set_layer_render(pdata, CD_MTEXPOLY, act);
+		CustomData_set_layer_render(ldata, CD_MLOOPUV, act);
+
+		act = CustomData_get_clone_layer(fdata, CD_MTFACE);
+		CustomData_set_layer_clone(pdata, CD_MTEXPOLY, act);
+		CustomData_set_layer_clone(ldata, CD_MLOOPUV, act);
+
+		act = CustomData_get_stencil_layer(fdata, CD_MTFACE);
+		CustomData_set_layer_stencil(pdata, CD_MTEXPOLY, act);
+		CustomData_set_layer_stencil(ldata, CD_MLOOPUV, act);
+	}
+
+	if (CustomData_has_layer(fdata, CD_MCOL)) {
+		act = CustomData_get_active_layer(fdata, CD_MCOL);
+		CustomData_set_layer_active(ldata, CD_MLOOPCOL, act);
+
+		act = CustomData_get_render_layer(fdata, CD_MCOL);
+		CustomData_set_layer_render(ldata, CD_MLOOPCOL, act);
+
+		act = CustomData_get_clone_layer(fdata, CD_MCOL);
+		CustomData_set_layer_clone(ldata, CD_MLOOPCOL, act);
+
+		act = CustomData_get_stencil_layer(fdata, CD_MCOL);
+		CustomData_set_layer_stencil(ldata, CD_MLOOPCOL, act);
+	}
+}
+
 void CustomData_bmesh_init_pool(CustomData *data, int totelem, const char htype)
 {
 	int chunksize;
diff --git a/source/blender/blenkernel/intern/mesh.c b/source/blender/blenkernel/intern/mesh.c
index ed93f27fe5c..d0b9e73e295 100644
--- a/source/blender/blenkernel/intern/mesh.c
+++ b/source/blender/blenkernel/intern/mesh.c
@@ -2038,6 +2038,28 @@ void BKE_mesh_convert_mfaces_to_mpolys(Mesh *mesh)
 	mesh_update_customdata_pointers(mesh, TRUE);
 }
 
+/* the same as BKE_mesh_convert_mfaces_to_mpolys but oriented to be used in do_versions from readfile.c
+ * the difference is how active/render/clone/stencil indices are handled here
+ *
+ * normally thay're being set from pdata which totally makes sense for meshes which are already
+ * converted to bmesh structures, but when loading older files indices shall be updated in other
+ * way around, so newly added pdata and ldata would have this indices set based on fdata layer
+ *
+ * this is normally only needed when reading older files, in all other cases BKE_mesh_convert_mfaces_to_mpolys
+ * shall be always used
+ */
+void BKE_mesh_do_versions_convert_mfaces_to_mpolys(Mesh *mesh)
+{
+	BKE_mesh_convert_mfaces_to_mpolys_ex(&mesh->id, &mesh->fdata, &mesh->ldata, &mesh->pdata,
+	                                     mesh->totedge, mesh->totface, mesh->totloop, mesh->totpoly,
+	                                     mesh->medge, mesh->mface,
+	                                     &mesh->totloop, &mesh->totpoly, &mesh->mloop, &mesh->mpoly);
+
+	CustomData_bmesh_do_versions_update_active_layers(&mesh->fdata, &mesh->pdata, &mesh->ldata);
+
+	mesh_update_customdata_pointers(mesh, TRUE);
+}
+
 void BKE_mesh_convert_mfaces_to_mpolys_ex(ID *id, CustomData *fdata, CustomData *ldata, CustomData *pdata,
                                           int totedge_i, int totface_i, int totloop_i, int totpoly_i,
                                           MEdge *medge, MFace *mface,
diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index 8fccae91870..cdf344beb4d 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -3684,7 +3684,7 @@ static void lib_link_mesh(FileData *fd, Main *main)
 				Main *gmain = G.main;
 				G.main = main;
 				
-				BKE_mesh_convert_mfaces_to_mpolys(me);
+				BKE_mesh_do_versions_convert_mfaces_to_mpolys(me);
 				
 				G.main = gmain;
 			}