Asset Browser: Support dragging assets into catalogs

With this it is possible to select any number of assets in the Asset
Browser and drag them into catalogs. The assets will be moved to that
catalog then. However, this will only work in the "Current File" asset
library, since that is the only library that allows changing assets,
which is what's done here.

While dragging assets over the tree row, a tooltip is shown explaining
what's going to happen.

In preparation to this, the new UI tree-view API was already extended
with custom drop support, see 4ee2d9df428d.

----

Changes here to the `wmDrag` code were needed to support dragging multiple
assets. Some of it is considered temporary because a) a proper #AssetHandle
design should replace some ugly parts of this patch and b) the multi-item
support in `wmDrag` isn't that great yet. The entire API will have to be
written anyway (see D4071).

Maniphest Tasks: T91573

Differential Revision: https://developer.blender.org/D12713

Reviewed by: Sybren Stüvel

1 files changed, 12 insertions, 4 deletions

diff --git a/source/blender/blenkernel/intern/asset_catalog.cc b/source/blender/blenkernel/intern/asset_catalog.cc
index 2c7cf28d60d..577d916288a 100644
--- a/source/blender/blenkernel/intern/asset_catalog.cc
+++ b/source/blender/blenkernel/intern/asset_catalog.cc
@@ -426,8 +426,9 @@ void AssetCatalogService::create_missing_catalogs()
 
 AssetCatalogTreeItem::AssetCatalogTreeItem(StringRef name,
                                            CatalogID catalog_id,
+                                           StringRef simple_name,
                                            const AssetCatalogTreeItem *parent)
-    : name_(name), catalog_id_(catalog_id), parent_(parent)
+    : name_(name), catalog_id_(catalog_id), simple_name_(simple_name), parent_(parent)
 {
 }
 
@@ -436,11 +437,16 @@ CatalogID AssetCatalogTreeItem::get_catalog_id() const
   return catalog_id_;
 }
 
-StringRef AssetCatalogTreeItem::get_name() const
+StringRefNull AssetCatalogTreeItem::get_name() const
 {
   return name_;
 }
 
+StringRefNull AssetCatalogTreeItem::get_simple_name() const
+{
+  return simple_name_;
+}
+
 AssetCatalogPath AssetCatalogTreeItem::catalog_path() const
 {
   AssetCatalogPath current_path = name_;
@@ -482,8 +488,10 @@ void AssetCatalogTree::insert_item(const AssetCatalog &catalog)
     /* Insert new tree element - if no matching one is there yet! */
     auto [key_and_item, was_inserted] = current_item_children->emplace(
         component_name,
-        AssetCatalogTreeItem(
-            component_name, is_last_component ? catalog.catalog_id : nil_id, parent));
+        AssetCatalogTreeItem(component_name,
+                             is_last_component ? catalog.catalog_id : nil_id,
+                             is_last_component ? catalog.simple_name : "",
+                             parent));
     AssetCatalogTreeItem &item = key_and_item->second;
 
     /* If full path of this catalog already exists as parent path of a previously read catalog,