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, 18 insertions, 17 deletions

diff --git a/source/blender/editors/space_outliner/outliner_draw.c b/source/blender/editors/space_outliner/outliner_draw.c
index 008ae727947..690adb09570 100644
--- a/source/blender/editors/space_outliner/outliner_draw.c
+++ b/source/blender/editors/space_outliner/outliner_draw.c
@@ -675,7 +675,7 @@ static void namebutton_fn(bContext *C, void *tsep, char *oldname)
   if (ts && tselem) {
     TreeElement *te = outliner_find_tree_element(&space_outliner->tree, tselem);
 
-    if (tselem->type == 0) {
+    if (tselem->type == TSE_SOME_ID) {
       BLI_libblock_ensure_unique_name(bmain, tselem->id->name);
 
       switch (GS(tselem->id->name)) {
@@ -1100,11 +1100,11 @@ static void outliner_draw_restrictbuts(uiBlock *block,
           UI_but_drawflag_enable(bt, UI_BUT_ICON_REVERSE);
         }
       }
-      else if ((tselem->type == 0 && te->idcode == ID_OB) &&
+      else if (((tselem->type == TSE_SOME_ID) && (te->idcode == ID_OB)) &&
                (te->flag & TE_CHILD_NOT_IN_COLLECTION)) {
         /* Don't show restrict columns for children that are not directly inside the collection. */
       }
-      else if (tselem->type == 0 && te->idcode == ID_OB) {
+      else if ((tselem->type == TSE_SOME_ID) && (te->idcode == ID_OB)) {
         PointerRNA ptr;
         Object *ob = (Object *)tselem->id;
         RNA_id_pointer_create(&ob->id, &ptr);
@@ -1699,7 +1699,7 @@ static void outliner_draw_userbuts(uiBlock *block,
   LISTBASE_FOREACH (TreeElement *, te, lb) {
     TreeStoreElem *tselem = TREESTORE(te);
     if (te->ys + 2 * UI_UNIT_Y >= region->v2d.cur.ymin && te->ys <= region->v2d.cur.ymax) {
-      if (tselem->type == 0) {
+      if (tselem->type == TSE_SOME_ID) {
         uiBut *bt;
         ID *id = tselem->id;
         const char *tip = NULL;
@@ -1949,7 +1949,7 @@ static void outliner_draw_mode_column_toggle(uiBlock *block,
                                              TreeStoreElem *tselem,
                                              const bool lock_object_modes)
 {
-  if (tselem->type != 0 || te->idcode != ID_OB) {
+  if ((tselem->type != TSE_SOME_ID) || (te->idcode != ID_OB)) {
     return;
   }
 
@@ -2046,7 +2046,7 @@ TreeElementIcon tree_element_get_icon(TreeStoreElem *tselem, TreeElement *te)
 {
   TreeElementIcon data = {0};
 
-  if (tselem->type) {
+  if (tselem->type != TSE_SOME_ID) {
     switch (tselem->type) {
       case TSE_ANIM_DATA:
         data.icon = ICON_ANIM_DATA; /* XXX */
@@ -2825,7 +2825,8 @@ int tree_element_id_type_to_index(TreeElement *te)
 {
   TreeStoreElem *tselem = TREESTORE(te);
 
-  const int id_index = tselem->type == 0 ? BKE_idtype_idcode_to_index(te->idcode) : INDEX_ID_GR;
+  const int id_index = (tselem->type == TSE_SOME_ID) ? BKE_idtype_idcode_to_index(te->idcode) :
+                                                       INDEX_ID_GR;
   if (id_index < INDEX_ID_OB) {
     return id_index;
   }
@@ -2862,9 +2863,9 @@ static void outliner_draw_iconrow(bContext *C,
     te->flag &= ~(TE_ICONROW | TE_ICONROW_MERGED);
 
     /* object hierarchy always, further constrained on level */
-    if (level < 1 || (tselem->type == 0 && te->idcode == ID_OB)) {
+    if ((level < 1) || ((tselem->type == TSE_SOME_ID) && (te->idcode == ID_OB))) {
       /* active blocks get white circle */
-      if (tselem->type == 0) {
+      if (tselem->type == TSE_SOME_ID) {
         if (te->idcode == ID_OB) {
           active = (tvc->obact == (Object *)tselem->id) ? OL_DRAWSEL_NORMAL : OL_DRAWSEL_NONE;
         }
@@ -2879,7 +2880,7 @@ static void outliner_draw_iconrow(bContext *C,
         active = tree_element_type_active_state_get(C, tvc, te, tselem);
       }
 
-      if (!ELEM(tselem->type, 0, TSE_LAYER_COLLECTION, TSE_R_LAYER, TSE_GP_LAYER)) {
+      if (!ELEM(tselem->type, TSE_SOME_ID, TSE_LAYER_COLLECTION, TSE_R_LAYER, TSE_GP_LAYER)) {
         outliner_draw_iconrow_doit(block, te, fstyle, xmax, offsx, ys, alpha_fac, active, 1);
       }
       else {
@@ -2954,7 +2955,7 @@ static bool element_should_draw_faded(const TreeViewContext *tvc,
                                       const TreeElement *te,
                                       const TreeStoreElem *tselem)
 {
-  if (tselem->type == 0) {
+  if (tselem->type == TSE_SOME_ID) {
     switch (te->idcode) {
       case ID_OB: {
         const Object *ob = (const Object *)tselem->id;
@@ -3023,7 +3024,7 @@ static void outliner_draw_tree_element(bContext *C,
     GPU_blend(GPU_BLEND_ALPHA);
 
     /* Colors for active/selected data. */
-    if (tselem->type == 0) {
+    if (tselem->type == TSE_SOME_ID) {
       if (te->idcode == ID_OB) {
         Object *ob = (Object *)tselem->id;
         Base *base = (te->directdata) ? (Base *)te->directdata :
@@ -3080,7 +3081,7 @@ static void outliner_draw_tree_element(bContext *C,
     if (tselem->type == TSE_VIEW_COLLECTION_BASE) {
       /* Scene collection in view layer can't expand/collapse. */
     }
-    else if (te->subtree.first || (tselem->type == 0 && te->idcode == ID_SCE) ||
+    else if (te->subtree.first || ((tselem->type == TSE_SOME_ID) && (te->idcode == ID_SCE)) ||
              (te->flag & TE_LAZY_CLOSED)) {
       /* Open/close icon, only when sub-levels, except for scene. */
       int icon_x = startx;
@@ -3117,7 +3118,7 @@ static void outliner_draw_tree_element(bContext *C,
       offsx += 2 * ufac;
     }
 
-    if (ELEM(tselem->type, 0, TSE_LAYER_COLLECTION) ||
+    if (ELEM(tselem->type, TSE_SOME_ID, TSE_LAYER_COLLECTION) ||
         ((tselem->type == TSE_RNA_STRUCT) && RNA_struct_is_ID(te->rnaptr.type))) {
       const BIFIconID lib_icon = UI_icon_from_library(tselem->id);
       if (lib_icon != ICON_NONE) {
@@ -3143,7 +3144,7 @@ static void outliner_draw_tree_element(bContext *C,
     /* Closed item, we draw the icons, not when it's a scene, or master-server list though. */
     if (!TSELEM_OPEN(tselem, space_outliner)) {
       if (te->subtree.first) {
-        if (tselem->type == 0 && te->idcode == ID_SCE) {
+        if ((tselem->type == TSE_SOME_ID) && (te->idcode == ID_SCE)) {
           /* Pass. */
         }
         /* this tree element always has same amount of branches, so don't draw */
@@ -3210,7 +3211,7 @@ static bool subtree_contains_object(ListBase *lb)
 {
   LISTBASE_FOREACH (TreeElement *, te, lb) {
     TreeStoreElem *tselem = TREESTORE(te);
-    if (tselem->type == 0 && te->idcode == ID_OB) {
+    if ((tselem->type == TSE_SOME_ID) && (te->idcode == ID_OB)) {
       return true;
     }
   }
@@ -3265,7 +3266,7 @@ static void outliner_draw_hierarchy_lines_recursive(uint pos,
 
         y = *starty;
       }
-      else if (tselem->type == 0 && te->idcode == ID_OB) {
+      else if ((tselem->type == TSE_SOME_ID) && (te->idcode == ID_OB)) {
         if (subtree_contains_object(&te->subtree)) {
           draw_hierarchy_line = true;
           is_object_line = true;