Cleanup: Add & use enum value for ID Outliner element type

Code to check if the Outliner tree-element type was the general ID one
would always check against "0" (explicity or even implicitly). For
somebody unfamiliar with the code this is very confusing. Instead the
value should be given a name, e.g. through an enum.

Adds `TSE_SOME_ID` as the "default" ID tree-element type. Other types
may still represent IDs, as I explained in a comment at the definition.

There may also still be cases where the type is checked against "0". I
noted in the comment that such cases should be cleaned up if found.

1 files changed, 5 insertions, 4 deletions

diff --git a/source/blender/editors/space_outliner/outliner_tools.c b/source/blender/editors/space_outliner/outliner_tools.c
index b735064cfef..9af2ba6a82b 100644
--- a/source/blender/editors/space_outliner/outliner_tools.c
+++ b/source/blender/editors/space_outliner/outliner_tools.c
@@ -106,7 +106,7 @@ static void get_element_operation_type(
   TreeStoreElem *tselem = TREESTORE(te);
   if (tselem->flag & TSE_SELECTED) {
     /* Layer collection points to collection ID. */
-    if (!ELEM(tselem->type, 0, TSE_LAYER_COLLECTION)) {
+    if (!ELEM(tselem->type, TSE_SOME_ID, TSE_LAYER_COLLECTION)) {
       if (*datalevel == 0) {
         *datalevel = tselem->type;
       }
@@ -402,7 +402,8 @@ static void outliner_do_libdata_operation(bContext *C,
   LISTBASE_FOREACH (TreeElement *, te, lb) {
     TreeStoreElem *tselem = TREESTORE(te);
     if (tselem->flag & TSE_SELECTED) {
-      if ((tselem->type == 0 && te->idcode != 0) || tselem->type == TSE_LAYER_COLLECTION) {
+      if (((tselem->type == TSE_SOME_ID) && (te->idcode != 0)) ||
+          tselem->type == TSE_LAYER_COLLECTION) {
         TreeStoreElem *tsep = te->parent ? TREESTORE(te->parent) : NULL;
         operation_fn(C, reports, scene, te, tsep, tselem, user_data);
       }
@@ -1044,7 +1045,7 @@ void outliner_do_object_operation_ex(bContext *C,
     TreeStoreElem *tselem = TREESTORE(te);
     bool select_handled = false;
     if (tselem->flag & TSE_SELECTED) {
-      if (tselem->type == 0 && te->idcode == ID_OB) {
+      if ((tselem->type == TSE_SOME_ID) && (te->idcode == ID_OB)) {
         /* When objects selected in other scenes... dunno if that should be allowed. */
         Scene *scene_owner = (Scene *)outliner_search_back(te, ID_SCE);
         if (scene_owner && scene_act != scene_owner) {
@@ -1601,7 +1602,7 @@ static TreeTraversalAction outliner_find_objects_to_delete(TreeElement *te, void
     return TRAVERSE_CONTINUE;
   }
 
-  if (tselem->type || (tselem->id == NULL) || (GS(tselem->id->name) != ID_OB)) {
+  if ((tselem->type != TSE_SOME_ID) || (tselem->id == NULL) || (GS(tselem->id->name) != ID_OB)) {
     return TRAVERSE_SKIP_CHILDS;
   }