Asset System: Support dragging assets and appending on drop

For the Asset Browser, it needs to be possible to drag assets into various
editors, which may not come from the current .blend file. In other words, the
dragging needs to work with just the asset metadata, without direct access to
the data-block itself.

Idea is simple: When dragging an asset, store the source file-path and
data-block name and when dropping, append the data-block. It uses existing drop
operators, but the function to get the dropped data-block is replaced with one
that returns the local data-block, or, in case of an external asset, appends
the data-block first.

The drop operators need to be adjusted to use this new function that respects
assets. With this patch it only works for dragging assets into the 3D view.

Note that I expect this to be a short-lived change. A refactor like D4071 is
needed to make the drag & drop system more future proof for assets and other
use cases.

Part of the first Asset Browser milestone. Check the #asset_browser_milestone_1
project milestone on developer.blender.org.

Differential Revision: https://developer.blender.org/D9721

Reviewed by: Bastien Montagne, Brecht Van Lommel

1 files changed, 18 insertions, 8 deletions

diff --git a/source/blender/editors/space_view3d/space_view3d.c b/source/blender/editors/space_view3d/space_view3d.c
index 9f31e7a411d..3761f4ad7c6 100644
--- a/source/blender/editors/space_view3d/space_view3d.c
+++ b/source/blender/editors/space_view3d/space_view3d.c
@@ -461,6 +461,12 @@ static void view3d_main_region_exit(wmWindowManager *wm, ARegion *region)
   ED_view3d_stop_render_preview(wm, region);
 }
 
+static bool view3d_drop_in_main_region_poll(bContext *C, const wmEvent *event)
+{
+  ScrArea *area = CTX_wm_area(C);
+  return ED_region_overlap_isect_any_xy(area, &event->x) == false;
+}
+
 static ID *view3d_drop_id_in_main_region_poll_id(bContext *C,
                                                  wmDrag *drag,
                                                  const wmEvent *event,
@@ -470,7 +476,7 @@ static ID *view3d_drop_id_in_main_region_poll_id(bContext *C,
   if (ED_region_overlap_isect_any_xy(area, &event->x)) {
     return NULL;
   }
-  return WM_drag_ID(drag, id_type);
+  return view3d_drop_in_main_region_poll(C, event) ? WM_drag_get_local_ID(drag, id_type) : NULL;
 }
 
 static bool view3d_drop_id_in_main_region_poll(bContext *C,
@@ -478,7 +484,11 @@ static bool view3d_drop_id_in_main_region_poll(bContext *C,
                                                const wmEvent *event,
                                                ID_Type id_type)
 {
-  return (view3d_drop_id_in_main_region_poll_id(C, drag, event, id_type) != NULL);
+  if (!view3d_drop_in_main_region_poll(C, event)) {
+    return false;
+  }
+
+  return WM_drag_get_local_ID(drag, id_type) || WM_drag_get_asset_data(drag, id_type);
 }
 
 static bool view3d_ob_drop_poll(bContext *C,
@@ -533,7 +543,7 @@ static bool view3d_ima_drop_poll(bContext *C,
     return (ELEM(drag->icon, 0, ICON_FILE_IMAGE, ICON_FILE_MOVIE));
   }
 
-  return WM_drag_ID(drag, ID_IM) != NULL;
+  return WM_drag_get_local_ID(drag, ID_IM) || WM_drag_get_asset_data(drag, ID_IM);
 }
 
 static bool view3d_ima_bg_is_camera_view(bContext *C)
@@ -596,14 +606,14 @@ static bool view3d_volume_drop_poll(bContext *UNUSED(C),
 
 static void view3d_ob_drop_copy(wmDrag *drag, wmDropBox *drop)
 {
-  ID *id = WM_drag_ID(drag, ID_OB);
+  ID *id = WM_drag_get_local_ID_or_import_from_asset(drag, ID_OB);
 
   RNA_string_set(drop->ptr, "name", id->name + 2);
 }
 
 static void view3d_collection_drop_copy(wmDrag *drag, wmDropBox *drop)
 {
-  ID *id = WM_drag_ID(drag, ID_GR);
+  ID *id = WM_drag_get_local_ID_or_import_from_asset(drag, ID_GR);
 
   drop->opcontext = WM_OP_EXEC_DEFAULT;
   RNA_string_set(drop->ptr, "name", id->name + 2);
@@ -611,14 +621,14 @@ static void view3d_collection_drop_copy(wmDrag *drag, wmDropBox *drop)
 
 static void view3d_id_drop_copy(wmDrag *drag, wmDropBox *drop)
 {
-  ID *id = WM_drag_ID(drag, 0);
+  ID *id = WM_drag_get_local_ID_or_import_from_asset(drag, 0);
 
   RNA_string_set(drop->ptr, "name", id->name + 2);
 }
 
 static void view3d_id_drop_copy_with_type(wmDrag *drag, wmDropBox *drop)
 {
-  ID *id = WM_drag_ID(drag, 0);
+  ID *id = WM_drag_get_local_ID(drag, 0);
 
   RNA_string_set(drop->ptr, "name", id->name + 2);
   RNA_enum_set(drop->ptr, "type", GS(id->name));
@@ -626,7 +636,7 @@ static void view3d_id_drop_copy_with_type(wmDrag *drag, wmDropBox *drop)
 
 static void view3d_id_path_drop_copy(wmDrag *drag, wmDropBox *drop)
 {
-  ID *id = WM_drag_ID(drag, 0);
+  ID *id = WM_drag_get_local_ID_or_import_from_asset(drag, 0);
 
   if (id) {
     RNA_string_set(drop->ptr, "name", id->name + 2);