source/blender/blenkernel/BKE_grease_pencil.hh

@@ -292,6 +292,12 @@ class LayerGroup : public ::GreasePencilLayerTreeGroup {
   Span<const Layer *> layers() const;
   Span<Layer *> layers_for_write();
 
+  /**
+   * Returns a pointer to the layer with \a name. If no such layer was found, returns nullptr.
+   */
+  const Layer *find_layer_by_name(StringRefNull name) const;
+  Layer *find_layer_by_name(StringRefNull name);
+
   /**
    * Print the nodes. For debugging purposes.
    */

source/blender/blenkernel/intern/grease_pencil.cc

@@ -103,6 +103,12 @@ static void grease_pencil_copy_data(Main * /*bmain*/,
   new (&grease_pencil_dst->root_group)
       bke::greasepencil::LayerGroup(grease_pencil_src->root_group.wrap());
 
+  /* Set active layer. */
+  if (grease_pencil_src->has_active_layer()) {
+    grease_pencil_dst->active_layer = grease_pencil_dst->find_layer_by_name(
+        grease_pencil_src->active_layer->wrap().name());
+  }
+
   /* Duplicate runtime data. */
   if (grease_pencil_src->runtime) {
     grease_pencil_dst->runtime = MEM_new<bke::GreasePencilRuntime>(__func__,
@@ -185,7 +191,6 @@ static void grease_pencil_blend_read_data(BlendDataReader *reader, ID *id)
   BLO_read_pointer_array(reader, reinterpret_cast<void **>(&grease_pencil->material_array));
 
   grease_pencil->runtime = MEM_new<blender::bke::GreasePencilRuntime>(__func__);
-  // grease_pencil->load_layer_tree_from_storage();
 }
 
 static void grease_pencil_blend_read_lib(BlendLibReader *reader, ID *id)
@@ -601,6 +606,26 @@ Span<Layer *> LayerGroup::layers_for_write()
   return this->runtime->layer_cache_.as_span();
 }
 
+const Layer *LayerGroup::find_layer_by_name(const StringRefNull name) const
+{
+  for (const Layer *layer : this->layers()) {
+    if (StringRef(layer->name()) == StringRef(name)) {
+      return layer;
+    }
+  }
+  return nullptr;
+}
+
+Layer *LayerGroup::find_layer_by_name(const StringRefNull name)
+{
+  for (Layer *layer : this->layers_for_write()) {
+    if (StringRef(layer->name()) == StringRef(name)) {
+      return layer;
+    }
+  }
+  return nullptr;
+}
+
 void LayerGroup::print_nodes(StringRefNull header) const
 {
   std::cout << header << std::endl;
@@ -615,10 +640,10 @@ void LayerGroup::print_nodes(StringRefNull header) const
       std::cout << "  ";
     }
     if (node->is_layer()) {
-      std::cout << node->name;
+      std::cout << StringRefNull(node->name);
     }
     else if (node->is_group()) {
-      std::cout << node->name << ": ";
+      std::cout << StringRefNull(node->name) << ": ";
       LISTBASE_FOREACH_BACKWARD (GreasePencilLayerTreeNode *, child_, &node->as_group().children) {
         TreeNode *child = reinterpret_cast<TreeNode *>(child_);
         next_node.push(std::make_pair(indent + 1, child));
@@ -626,6 +651,7 @@ void LayerGroup::print_nodes(StringRefNull header) const
     }
     std::cout << std::endl;
   }
+  std::cout << std::endl;
 }
 
 void LayerGroup::ensure_nodes_cache() const
@@ -1054,6 +1080,27 @@ blender::Span<blender::bke::greasepencil::Layer *> GreasePencil::layers_for_writ
   return this->root_group.wrap().layers_for_write();
 }
 
+blender::bke::greasepencil::Layer &GreasePencil::add_layer(
+    blender::bke::greasepencil::LayerGroup &group, const blender::StringRefNull name)
+{
+  using namespace blender;
+  StringRefNull checked_name;
+  /* TODO: Check for name collisions and resolve them. */
+  return group.add_layer(name);
+}
+
+const blender::bke::greasepencil::Layer *GreasePencil::find_layer_by_name(
+    const blender::StringRefNull name) const
+{
+  return this->root_group.wrap().find_layer_by_name(name);
+}
+
+blender::bke::greasepencil::Layer *GreasePencil::find_layer_by_name(
+    const blender::StringRefNull name)
+{
+  return this->root_group.wrap().find_layer_by_name(name);
+}
+
 void GreasePencil::print_layer_tree()
 {
   using namespace blender::bke::greasepencil;

source/blender/blenkernel/intern/grease_pencil_convert_legacy.cc

@@ -188,10 +188,11 @@ void legacy_gpencil_to_grease_pencil(Main &bmain, GreasePencil &grease_pencil, b
       MEM_cnew_array<GreasePencilDrawing *>(num_drawings, __func__));
 
   int i = 0, layer_idx = 0;
-  LayerGroup &root_goup = grease_pencil.root_group.wrap();
+  LayerGroup &root_group = grease_pencil.root_group.wrap();
   LISTBASE_FOREACH_INDEX (bGPDlayer *, gpl, &gpd.layers, layer_idx) {
     /* Create a new layer. */
-    Layer &new_layer = root_goup.add_layer(StringRefNull(gpl->info, BLI_strnlen(gpl->info, 128)));
+    Layer &new_layer = grease_pencil.add_layer(
+        root_group, StringRefNull(gpl->info, BLI_strnlen(gpl->info, 128)));
 
     /* Flags. */
     SET_FLAG_FROM_TEST(new_layer.base.flag, (gpl->flag & GP_LAYER_HIDE), GP_LAYER_TREE_NODE_HIDE);
@@ -239,8 +240,6 @@ void legacy_gpencil_to_grease_pencil(Main &bmain, GreasePencil &grease_pencil, b
     }
 
     /* TODO: Update drawing user counts. */
-
-    new_layer.tag_frames_map_keys_changed();
   }
 
   /* Convert the onion skinning settings. */
@@ -257,8 +256,6 @@ void legacy_gpencil_to_grease_pencil(Main &bmain, GreasePencil &grease_pencil, b
   copy_v3_v3(grease_pencil.onion_skinning_settings.color_before, gpd.gcolor_prev);
   copy_v3_v3(grease_pencil.onion_skinning_settings.color_after, gpd.gcolor_next);
 
-  // grease_pencil.runtime->set_active_layer_index(active_layer_index);
-
   BKE_id_materials_copy(&bmain, &gpd.id, &grease_pencil.id);
 }
 

source/blender/makesdna/DNA_grease_pencil_types.h

@@ -442,6 +442,12 @@ typedef struct GreasePencil {
   blender::Span<blender::bke::greasepencil::Layer *> layers_for_write();
 
   bool has_active_layer() const;
+  blender::bke::greasepencil::Layer &add_layer(blender::bke::greasepencil::LayerGroup &group,
+                                               blender::StringRefNull name);
+
+  const blender::bke::greasepencil::Layer *find_layer_by_name(blender::StringRefNull name) const;
+  blender::bke::greasepencil::Layer *find_layer_by_name(blender::StringRefNull name);
+
   void add_empty_drawings(int add_size);
   void remove_drawing(int index);