guiconfig: Check for visible nodes before turning off show-all in full-tree mode

If there are no visible nodes in the entire tree, guiconfig
automatically starts in show-all mode. Previously, there was no check
for visible nodes when turning off show-all in full-tree mode in this
case, leading to errors.

Fix it by checking if there are any visible nodes in the top menu when
turning off show-all in full-tree mode. If there aren't, show-all stays
on.

1 files changed, 13 insertions, 3 deletions

diff --git a/guiconfig.py b/guiconfig.py
index 20ecfa1..d333be4 100755
--- a/guiconfig.py
+++ b/guiconfig.py
@@ -1475,9 +1475,8 @@ def _toggle_showall(_):
 def _do_showall():
     # Updates the UI for the current show-all setting
 
-    # Don't allow turning off show-all if we're in single-menu mode and the
-    # current menu would become empty
-    if _single_menu and not _shown_menu_nodes(_cur_menu):
+    # Don't allow turning off show-all if we'd end up with no visible nodes
+    if _nothing_shown():
         _show_all_var.set(True)
         return
 
@@ -1512,6 +1511,17 @@ def _do_showall():
     _tree.focus_set()
 
 
+def _nothing_shown():
+    # _do_showall() helper. Returns True if no nodes would get
+    # shown with the current show-all setting. Also handles the
+    # (obscure) case when there are no visible nodes in the entire
+    # tree, meaning guiconfig was automatically started in
+    # show-all mode, which mustn't be turned off.
+
+    return not _shown_menu_nodes(
+        _cur_menu if _single_menu else _kconf.top_node)
+
+
 def _toggle_tree_mode(_):
     # Toggles single-menu mode on/off