App tree: keep expanded folders open; only the - sign closes one

Rebuilding the tree (live child loads, edits) now restores every row that
was expanded, matched by component id or name path. Double-click no longer
toggles a row through ttk's default binding.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

sax_file.py

@@ -59,9 +59,53 @@ def parse_xml_to_tree(treeview, parent_node, xml_element):
             parse_xml_to_tree(treeview, node_id, child)
 
 
+def _expansion_key(treeview, item, parent_key):
+    """Names a tree row in a way that survives a rebuild of the tree.
+
+    A component's id is stable across edits and across a fresh DOM read from the
+    device; a row without one (the root, or an id-less file component) falls back to
+    its name under its parent's key.
+    """
+    elem = app_state.tree_element_map.get(item)
+    comp_id = elem.get("id") if elem is not None else None
+    if comp_id is not None and treeview.parent(item) != "":
+        return ("id", comp_id)
+    name = elem.get("name", "") if elem is not None else treeview.item(item, "text")
+    return ("path", parent_key, name)
+
+
+def _collect_open_keys(treeview, parent="", parent_key=None, found=None):
+    """Returns the keys of every row that is expanded right now."""
+    if found is None:
+        found = set()
+    for item in treeview.get_children(parent):
+        key = _expansion_key(treeview, item, parent_key)
+        if treeview.item(item, "open"):
+            found.add(key)
+        _collect_open_keys(treeview, item, key, found)
+    return found
+
+
+def _reopen_keys(treeview, open_keys, parent="", parent_key=None):
+    """Expands again the rows that were expanded before the rebuild.
+
+    Setting the open flag in code does not raise <<TreeviewOpen>>, so this never
+    starts a live child load of its own.
+    """
+    for item in treeview.get_children(parent):
+        key = _expansion_key(treeview, item, parent_key)
+        if key in open_keys:
+            treeview.item(item, open=True)
+        _reopen_keys(treeview, open_keys, item, key)
+
+
 def refresh_treeview_from_dom(xml_root):
-    """Rebuilds navigation tree structures using current XML DOM trees."""
+    """Rebuilds navigation tree structures using current XML DOM trees.
+
+    Rows the user had expanded stay expanded; only the user's own "-" closes one.
+    """
     tree = app_state.tree
+    open_keys = _collect_open_keys(tree)
     app_state.tree_element_map.clear()
 
     for item in tree.get_children():
@@ -88,6 +132,8 @@ def refresh_treeview_from_dom(xml_root):
     else:
         parse_xml_to_tree(tree, root_node, xml_root)
 
+    _reopen_keys(tree, open_keys)
+
     if _tree_filled is not None:
         _tree_filled()