Assets: allow creating preview image by rendering active object

For node groups there is no good default preview generation.
Nevertheless, t would be useful to generate a preview image for a
node group by rendering an object in some cases.

This commit adds a new operator that allows updating the preview
image for the active asset by rendering the active object.
Note, the operator can also be used for other asset types, not just
node groups.

The operator can be found in a menu right below the refresh-preview
button. Currently it is the only operator in that menu. In the future,
more operators to create previews may be added.

Differential Revision: https://developer.blender.org/D13747

3 files changed, 91 insertions, 4 deletions

diff --git a/source/blender/editors/include/UI_interface_icons.h b/source/blender/editors/include/UI_interface_icons.h
index 6ffeb4134ae..1009ae5cd3f 100644
--- a/source/blender/editors/include/UI_interface_icons.h
+++ b/source/blender/editors/include/UI_interface_icons.h
@@ -82,6 +82,8 @@ int UI_icon_get_height(int icon_id);
 bool UI_icon_get_theme_color(int icon_id, unsigned char color[4]);
 
 /**
+ * Render a #PreviewImage for the data block.
+ *
  * Note that if an ID doesn't support jobs for preview creation, \a use_job will be ignored.
  */
 void UI_icon_render_id(const struct bContext *C,
@@ -89,6 +91,18 @@ void UI_icon_render_id(const struct bContext *C,
                        struct ID *id,
                        enum eIconSizes size,
                        bool use_job);
+
+/**
+ * Render the data block into the provided #PreviewImage.
+ */
+void UI_icon_render_id_ex(const struct bContext *C,
+                          struct Scene *scene,
+                          struct ID *id_to_render,
+                          const enum eIconSizes size,
+                          const bool use_job,
+                          struct PreviewImage *r_preview_image);
+
+
 /**
  * Render size for preview images and icons
  */
diff --git a/source/blender/editors/interface/interface_icons.c b/source/blender/editors/interface/interface_icons.c
index 0f5b4a1a0f1..c0d6b8a1a6c 100644
--- a/source/blender/editors/interface/interface_icons.c
+++ b/source/blender/editors/interface/interface_icons.c
@@ -1949,6 +1949,16 @@ static void ui_id_preview_image_render_size(
   }
 }
 
+void UI_icon_render_id_ex(const bContext *C,
+                          Scene *scene,
+                          ID *id_to_render,
+                          const enum eIconSizes size,
+                          const bool use_job,
+                          PreviewImage *r_preview_image)
+{
+  ui_id_preview_image_render_size(C, scene, id_to_render, r_preview_image, size, use_job);
+}
+
 void UI_icon_render_id(
     const bContext *C, Scene *scene, ID *id, const enum eIconSizes size, const bool use_job)
 {
@@ -1957,19 +1967,21 @@ void UI_icon_render_id(
     return;
   }
 
+  ID *id_to_render = id;
+
   /* For objects, first try if a preview can created via the object data. */
   if (GS(id->name) == ID_OB) {
     Object *ob = (Object *)id;
     if (ED_preview_id_is_supported(ob->data)) {
-      id = ob->data;
+      id_to_render = ob->data;
     }
   }
 
-  if (!ED_preview_id_is_supported(id)) {
+  if (!ED_preview_id_is_supported(id_to_render)) {
     return;
   }
 
-  ui_id_preview_image_render_size(C, scene, id, pi, size, use_job);
+  UI_icon_render_id_ex(C, scene, id_to_render, size, use_job, pi);
 }
 
 static void ui_id_icon_render(const bContext *C, ID *id, bool use_jobs)
diff --git a/source/blender/editors/util/ed_util_ops.cc b/source/blender/editors/util/ed_util_ops.cc
index a1b17d799bc..ae37dab7bb4 100644
--- a/source/blender/editors/util/ed_util_ops.cc
+++ b/source/blender/editors/util/ed_util_ops.cc
@@ -121,6 +121,22 @@ static void ED_OT_lib_id_load_custom_preview(wmOperatorType *ot)
                                  FILE_SORT_DEFAULT);
 }
 
+static bool lib_id_generate_preview_poll(bContext *C)
+{
+  if (!lib_id_preview_editing_poll(C)) {
+    return false;
+  }
+
+  const PointerRNA idptr = CTX_data_pointer_get(C, "id");
+  const ID *id = (ID *)idptr.data;
+  if (GS(id->name) == ID_NT) {
+    CTX_wm_operator_poll_msg_set(C, TIP_("Can't generate automatic preview for node group"));
+    return false;
+  }
+
+  return true;
+}
+
 static int lib_id_generate_preview_exec(bContext *C, wmOperator *UNUSED(op))
 {
   PointerRNA idptr = CTX_data_pointer_get(C, "id");
@@ -148,13 +164,57 @@ static void ED_OT_lib_id_generate_preview(wmOperatorType *ot)
   ot->idname = "ED_OT_lib_id_generate_preview";
 
   /* api callbacks */
-  ot->poll = lib_id_preview_editing_poll;
+  ot->poll = lib_id_generate_preview_poll;
   ot->exec = lib_id_generate_preview_exec;
 
   /* flags */
   ot->flag = OPTYPE_INTERNAL | OPTYPE_REGISTER | OPTYPE_UNDO;
 }
 
+static bool lib_id_generate_preview_from_object_poll(bContext *C)
+{
+  if (!lib_id_preview_editing_poll(C)) {
+    return false;
+  }
+  if (CTX_data_active_object(C) == nullptr) {
+    return false;
+  }
+  return true;
+}
+
+static int lib_id_generate_preview_from_object_exec(bContext *C, wmOperator *UNUSED(op))
+{
+  PointerRNA idptr = CTX_data_pointer_get(C, "id");
+  ID *id = (ID *)idptr.data;
+
+  ED_preview_kill_jobs(CTX_wm_manager(C), CTX_data_main(C));
+
+  Object *object_to_render = CTX_data_active_object(C);
+
+  BKE_previewimg_id_free(id);
+  PreviewImage *preview_image = BKE_previewimg_id_ensure(id);
+  UI_icon_render_id_ex(C, nullptr, &object_to_render->id, ICON_SIZE_PREVIEW, true, preview_image);
+
+  WM_event_add_notifier(C, NC_ASSET | NA_EDITED, nullptr);
+  ED_assetlist_storage_tag_main_data_dirty();
+
+  return OPERATOR_FINISHED;
+}
+
+static void ED_OT_lib_id_generate_preview_from_object(wmOperatorType *ot)
+{
+  ot->name = "Generate Preview from Object";
+  ot->description = "Create a preview for this asset by rendering the active object";
+  ot->idname = "ED_OT_lib_id_generate_preview_from_object";
+
+  /* api callbacks */
+  ot->poll = lib_id_generate_preview_from_object_poll;
+  ot->exec = lib_id_generate_preview_from_object_exec;
+
+  /* flags */
+  ot->flag = OPTYPE_INTERNAL | OPTYPE_REGISTER | OPTYPE_UNDO;
+}
+
 /** \} */
 
 /* -------------------------------------------------------------------- */
@@ -280,6 +340,7 @@ void ED_operatortypes_edutils()
 {
   WM_operatortype_append(ED_OT_lib_id_load_custom_preview);
   WM_operatortype_append(ED_OT_lib_id_generate_preview);
+  WM_operatortype_append(ED_OT_lib_id_generate_preview_from_object);
 
   WM_operatortype_append(ED_OT_lib_id_fake_user_toggle);
   WM_operatortype_append(ED_OT_lib_id_unlink);