From 0c5369cd9d2492f7da8ed47f0879f730c92b3378 Mon Sep 17 00:00:00 2001
From: Joscha <joscha@plugh.de>
Date: Sun, 12 May 2019 10:59:38 +0000
Subject: [PATCH] Fix drawing of non-top-level anchors

---
 cheuph/element_supply.py | 53 +++++++++++++++++-----------------------
 cheuph/tree_display.py   |  5 ++--
 2 files changed, 26 insertions(+), 32 deletions(-)

diff --git a/cheuph/element_supply.py b/cheuph/element_supply.py
index 885a969..9f5ca4e 100644
--- a/cheuph/element_supply.py
+++ b/cheuph/element_supply.py
@@ -69,14 +69,6 @@ class ElementSupply(abc.ABC):
 
         return children
 
-    # There is not a clear-cut way to get the previous or next "sibling" of an
-    # element that is itself a child of the implicit root (None), since
-    # get_children() doesn't accept None in its element_id argument.
-    #
-    # Because of this, the get_previous_id() and get_next_id() functions are
-    # abstract (until I decide to change the signature of get_children(), that
-    # is :P).
-
     def get_previous_id(self, element_id: Id) -> Optional[Id]:
         """
         Get the id of an element's previous sibling (i. e. the sibling just
@@ -139,28 +131,29 @@ class ElementSupply(abc.ABC):
         else:
             return None
 
-#    def get_furthest_ancestor_id(self,
-#            element_id: Id,
-#            root_id: Optional[Id] = None,
-#            ) -> Id:
-#        current_id = element_id
-#
-#        while True:
-#            parent_id = self.get_parent_id(current_id)
-#
-#            if parent_id == root_id:
-#                return current_id
-#            elif parent_id is None:
-#                raise TreeException("Reached implicit root before hitting specified root")
-#
-#            current_id = parent_id
-#
-#    def get_furthest_ancestor(self,
-#            element_id: Id,
-#            root_id: Optional[Id] = None,
-#            ) -> Element:
-#        return self.get(self.get_furthest_ancestor_id(element_id,
-#            root_id=root_id))
+    def get_furthest_ancestor_id(self,
+            element_id: Id,
+            root_id: Optional[Id] = None,
+            ) -> Id:
+        current_id = element_id
+
+        while True:
+            parent_id = self.get_parent_id(current_id)
+
+            if parent_id == root_id:
+                return current_id
+            elif parent_id is None:
+                raise TreeException(
+                    "Reached implicit root before hitting specified root")
+
+            current_id = parent_id
+
+    def get_furthest_ancestor(self,
+            element_id: Id,
+            root_id: Optional[Id] = None,
+            ) -> Element:
+        return self.get(self.get_furthest_ancestor_id(element_id,
+            root_id=root_id))
 
 class MemoryElementSupply(ElementSupply):
     """
diff --git a/cheuph/tree_display.py b/cheuph/tree_display.py
index a51bd6e..d75f923 100644
--- a/cheuph/tree_display.py
+++ b/cheuph/tree_display.py
@@ -195,9 +195,10 @@ class TreeDisplay:
             self._rendered = None
             return
 
-        anchor_tree = self._render_tree(self.anchor_id)
+        ancestor_id = self._supply.get_furthest_ancestor_id(self.anchor_id)
+        ancestor_tree = self._render_tree(ancestor_id)
 
-        self._rendered = TreeList(anchor_tree, self.anchor_id)
+        self._rendered = TreeList(ancestor_tree, self.anchor_id)
         self._rendered.offset_by(self.anchor_offset)
 
         self._fill_screen_upwards()