Outliner: Left and right walk navigation

Previously the left and right arrow keys would close and open the active
tree element, but a subsequent key press would not select up or
down the tree as is common in tree-based interfaces.

Walking left and right now does a selection action after opening or closing
the active tree item. For example, a right key press on a closed element
will open it's subtree, and an additional right key press will select
the first child element.

A left key press anywhere in a subtree will first close the active
element if it's subtree is expanded. Walking left again will select the
parent element.

Part of T77408

Differential Revision: https://developer.blender.org/D8650

1 files changed, 4 insertions, 1 deletions

diff --git a/source/blender/editors/space_outliner/outliner_edit.c b/source/blender/editors/space_outliner/outliner_edit.c
index 8567dd4da13..99eb9a04c0e 100644
--- a/source/blender/editors/space_outliner/outliner_edit.c
+++ b/source/blender/editors/space_outliner/outliner_edit.c
@@ -152,8 +152,11 @@ void OUTLINER_OT_highlight_update(wmOperatorType *ot)
 /* Open or close a tree element, optionally toggling all children recursively */
 void outliner_item_openclose(TreeElement *te, bool open, bool toggle_all)
 {
-  TreeStoreElem *tselem = TREESTORE(te);
+  if (BLI_listbase_is_empty(&te->subtree)) {
+    return;
+  }
 
+  TreeStoreElem *tselem = TREESTORE(te);
   if (open) {
     tselem->flag &= ~TSE_CLOSED;
   }