add get_subcursor()

nested/src/tree/cursor.rs

@@ -24,6 +24,17 @@ impl TreeCursor {
             tree_addr: vec![],
         }
     }
+
+    pub fn get_subcursor(&self, depth: usize) -> TreeCursor {
+        TreeCursor {
+            leaf_mode: self.leaf_mode,
+            tree_addr: if depth < self.tree_addr.len() {
+                self.tree_addr[ depth.. ].iter().cloned().collect()
+            } else {
+                vec![]
+            }
+        }
+    }
 }
 
 impl Default for TreeCursor {

nested/src/tree/nav.rs

@@ -181,3 +181,4 @@ pub trait TreeNav {
     }
 }
 
+

nested/src/tree/node.rs

@@ -34,16 +34,13 @@ struct NestedNodeEdit {
                     Option< Arc<dyn Any + Send + Sync> >
     >,
 
-    pub input_buf:: VecBuffer< NestedNode >,
-    pub output_buf: VecBuffer< NestedNode >,
+    pub spillbuf: VecBuffer< NestedNode >,
 
     /// commander & navigation
     pub cmd: SingletonBuffer<
                  Option< Arc<RwLock<dyn ObjCommander + Send + Sync>> >
              >,
-    pub close_char: SingletonBuffer<
-                        Option< char >
-            >,
+    pub close_char: SingletonBuffer< Option< char > >,
 
     // could be replaced by cmd when TreeNav -CmdObjects are used
     pub tree_nav: SingletonBuffer<

nested/src/tree/treetype.rs

@@ -7,8 +7,8 @@ use {
 };
 
 pub trait TreeType {
-    fn get_type(&self, _addr: &TreeAddr) -> TypeTerm {
-        TypeTerm::new(TypeID::Var(0))
+    fn get_type(&self, addr: &TreeAddr) -> Vec<TypeTerm> {
+        vec![]
     }
 }