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.

3 files changed, 18 insertions, 0 deletions

diff --git a/source/blender/windowmanager/WM_api.h b/source/blender/windowmanager/WM_api.h
index 26db02be289..b5acecc4762 100644
--- a/source/blender/windowmanager/WM_api.h
+++ b/source/blender/windowmanager/WM_api.h
@@ -770,6 +770,8 @@ void WM_drag_free_imported_drag_ID(struct Main *bmain,
                                    struct wmDrag *drag,
                                    struct wmDropBox *drop);
 
+struct wmDragAssetCatalog *WM_drag_get_asset_catalog_data(const struct wmDrag *drag);
+
 void WM_drag_add_asset_list_item(wmDrag *drag,
                                  const struct bContext *C,
                                  const struct AssetLibraryReference *asset_library_ref,
diff --git a/source/blender/windowmanager/WM_types.h b/source/blender/windowmanager/WM_types.h
index 1f1b1a70685..9f427a90353 100644
--- a/source/blender/windowmanager/WM_types.h
+++ b/source/blender/windowmanager/WM_types.h
@@ -119,6 +119,7 @@ struct wmWindowManager;
 
 #include "BLI_compiler_attrs.h"
 #include "DNA_listBase.h"
+#include "DNA_uuid_types.h"
 #include "DNA_vec_types.h"
 #include "DNA_xr_types.h"
 #include "RNA_types.h"
@@ -967,6 +968,7 @@ typedef void (*wmPaintCursorDraw)(struct bContext *C, int, int, void *customdata
 #define WM_DRAG_VALUE 6
 #define WM_DRAG_COLOR 7
 #define WM_DRAG_DATASTACK 8
+#define WM_DRAG_ASSET_CATALOG 9
 
 typedef enum wmDragFlags {
   WM_DRAG_NOP = 0,
@@ -1000,6 +1002,10 @@ typedef struct wmDragAsset {
   struct bContext *evil_C;
 } wmDragAsset;
 
+typedef struct wmDragAssetCatalog {
+  bUUID drag_catalog_id;
+} wmDragAssetCatalog;
+
 /**
  * For some specific cases we support dragging multiple assets (#WM_DRAG_ASSET_LIST). There is no
  * proper support for dragging multiple items in the `wmDrag`/`wmDrop` API yet, so this is really
diff --git a/source/blender/windowmanager/intern/wm_dragdrop.c b/source/blender/windowmanager/intern/wm_dragdrop.c
index 50ac046ed54..df6d3d5e9e7 100644
--- a/source/blender/windowmanager/intern/wm_dragdrop.c
+++ b/source/blender/windowmanager/intern/wm_dragdrop.c
@@ -181,6 +181,7 @@ wmDrag *WM_event_start_drag(
       }
       break;
     case WM_DRAG_ASSET:
+    case WM_DRAG_ASSET_CATALOG:
       /* Move ownership of poin to wmDrag. */
       drag->poin = poin;
       drag->flags |= WM_DRAG_FREE_DATA;
@@ -649,6 +650,15 @@ void WM_drag_free_imported_drag_ID(struct Main *bmain, wmDrag *drag, wmDropBox *
   }
 }
 
+wmDragAssetCatalog *WM_drag_get_asset_catalog_data(const wmDrag *drag)
+{
+  if (drag->type != WM_DRAG_ASSET_CATALOG) {
+    return NULL;
+  }
+
+  return drag->poin;
+}
+
 /**
  * \note: Does not store \a asset in any way, so it's fine to pass a temporary.
  */