Outliner: Make use of new C++ based functional iterators

(Not meant to cause user visible changes.)

Makes use of the new iterators introduced in the previous commit. Some
benefits:
- Shorter, simpler, easier to read & understand
- Deduplicates logic
- Centralizes iteration logic, making it easier to replace tree storage
  (as planned), see previous commit.
- Avoids having to pass (sub-)tree to iterate around (often redundant
  since it's just `SpaceOutliner.tree`, even though `SpaceOutliner` is
  already passed).
- Function arguments that are only passed to the recursive call are
  recognized as unused (found and removed a few).

Also does some general cleanups while refactoring the code for the
iterators. Use `const`, use references (signals null is not expected),
early-exit (see 16fd5fa656af), remove redundant arguments, etc.

1 files changed, 1 insertions, 1 deletions

diff --git a/source/blender/editors/space_outliner/space_outliner.cc b/source/blender/editors/space_outliner/space_outliner.cc
index 97dc659155f..5bcd1edebc0 100644
--- a/source/blender/editors/space_outliner/space_outliner.cc
+++ b/source/blender/editors/space_outliner/space_outliner.cc
@@ -438,7 +438,7 @@ static void outliner_deactivate(struct ScrArea *area)
 {
   /* Remove hover highlights */
   SpaceOutliner *space_outliner = reinterpret_cast<SpaceOutliner *>(area->spacedata.first);
-  outliner_flag_set(&space_outliner->tree, TSE_HIGHLIGHTED_ANY, false);
+  outliner_flag_set(*space_outliner, TSE_HIGHLIGHTED_ANY, false);
   ED_region_tag_redraw_no_rebuild(BKE_area_find_region_type(area, RGN_TYPE_WINDOW));
 }