Asset Browser: Support dragging catalogs to move them in the hierarchy

Uses the additions to the UI tree-view API from the previous commit to
enable drag & drop of asset catalogs. The catalogs will be moved in the
tree including children.
A remaining issue is that a catalog with children will always be
collapsed when dropping. I need to find a way to fix that in the
tree-view API.

There are a few improvements I can think of for the tree-item drag &
drop support, but time for these is too short. These can be done as
normal cleanups at some point.

2 files changed, 30 insertions, 0 deletions

diff --git a/source/blender/editors/asset/ED_asset_catalog.hh b/source/blender/editors/asset/ED_asset_catalog.hh
index 8b8fc4d3574..8da8fc0d6c9 100644
--- a/source/blender/editors/asset/ED_asset_catalog.hh
+++ b/source/blender/editors/asset/ED_asset_catalog.hh
@@ -37,3 +37,6 @@ void ED_asset_catalog_remove(AssetLibrary *library, const blender::bke::CatalogI
 void ED_asset_catalog_rename(AssetLibrary *library,
                              blender::bke::CatalogID catalog_id,
                              blender::StringRefNull new_name);
+void ED_asset_catalog_move(AssetLibrary *library,
+                           blender::bke::CatalogID src_catalog_id,
+                           blender::bke::CatalogID dst_parent_catalog_id);
diff --git a/source/blender/editors/asset/intern/asset_catalog.cc b/source/blender/editors/asset/intern/asset_catalog.cc
index f3ba12a6324..8e1e5be2e47 100644
--- a/source/blender/editors/asset/intern/asset_catalog.cc
+++ b/source/blender/editors/asset/intern/asset_catalog.cc
@@ -121,6 +121,33 @@ void ED_asset_catalog_rename(::AssetLibrary *library,
   WM_main_add_notifier(NC_SPACE | ND_SPACE_ASSET_PARAMS, nullptr);
 }
 
+void ED_asset_catalog_move(::AssetLibrary *library,
+                           const CatalogID src_catalog_id,
+                           const CatalogID dst_parent_catalog_id)
+{
+  bke::AssetCatalogService *catalog_service = BKE_asset_library_get_catalog_service(library);
+  if (!catalog_service) {
+    BLI_assert_unreachable();
+    return;
+  }
+
+  AssetCatalog *src_catalog = catalog_service->find_catalog(src_catalog_id);
+  AssetCatalog *dst_catalog = catalog_service->find_catalog(dst_parent_catalog_id);
+
+  const AssetCatalogPath new_path = dst_catalog->path / StringRef(src_catalog->path.name());
+  const AssetCatalogPath clean_new_path = new_path.cleanup();
+
+  if (new_path == src_catalog->path || clean_new_path == src_catalog->path) {
+    /* Nothing changed, so don't bother renaming for nothing. */
+    return;
+  }
+
+  catalog_service->undo_push();
+  catalog_service->tag_has_unsaved_changes(src_catalog);
+  catalog_service->update_catalog_path(src_catalog_id, clean_new_path);
+  WM_main_add_notifier(NC_SPACE | ND_SPACE_ASSET_PARAMS, nullptr);
+}
+
 void ED_asset_catalogs_save_from_main_path(::AssetLibrary *library, const Main *bmain)
 {
   bke::AssetCatalogService *catalog_service = BKE_asset_library_get_catalog_service(library);