Palette: reopen the last chosen kit instead of starting empty

The chosen kit is remembered in editor.properties [Palette]; a file without it
opens on its first kit. Saving preferences now keeps the other sections.

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

app_state.py

@@ -8,7 +8,7 @@ so later rebinding would only ever be seen by the module that did it.
 import configparser
 import os
 
-VERSION = "0.0.0.153"
+VERSION = "0.0.0.154"
 PROPERTIES_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)), "editor.properties")
 DEFAULT_GRID_SIZE = 10
 DEFAULT_ADD_TIMESTAMP = True
@@ -148,8 +148,15 @@ def load_preferences():
 
 
 def save_preferences():
-    """Writes the current preference values back to editor.properties."""
+    """Writes the current preference values back to editor.properties.
+
+    The file is read first so the sections other code owns ([Device], [Palette]) survive.
+    """
     config = configparser.ConfigParser()
+    try:
+        config.read(PROPERTIES_FILE)
+    except Exception:
+        pass
     config["Editor"] = {
         "sedona.home": SEDONA_HOME,
         "grid_size": str(GRID_SIZE),
@@ -162,6 +169,32 @@ def save_preferences():
         config.write(configfile)
 
 
+def load_last_palette_kit():
+    """The kit the palette dropdown showed last, or "" when none was ever chosen."""
+    config = configparser.ConfigParser()
+    try:
+        config.read(PROPERTIES_FILE)
+        return config.get("Palette", "kit", fallback="").strip()
+    except Exception:
+        return ""
+
+
+def save_last_palette_kit(kit_name):
+    """Remembers the palette's kit so the next start, or a kit refresh, reopens it."""
+    global LAST_PALETTE_KIT
+    LAST_PALETTE_KIT = kit_name
+    config = configparser.ConfigParser()
+    try:
+        config.read(PROPERTIES_FILE)
+        if "Palette" not in config:
+            config["Palette"] = {}
+        config["Palette"]["kit"] = kit_name
+        with open(PROPERTIES_FILE, "w") as configfile:
+            config.write(configfile)
+    except Exception:
+        pass
+
+
 def base_window_title():
     """The window title with no file context, which handlers extend with their own suffix."""
     return f"Sedona SAX Offline Program Editor [v{VERSION}]"
@@ -221,3 +254,4 @@ def base_window_title_live():
 
 
 SEDONA_HOME, GRID_SIZE, ADD_TIMESTAMP, BOX_WIDTH, LEFT_PANE_WIDTH, TRACE_DASP = load_preferences()
+LAST_PALETTE_KIT = load_last_palette_kit()

main.py

@@ -2980,6 +2980,8 @@ def populate_palette_types(event=None):
         return
 
     kit_name = palette_kit_names[index]
+    if event is not None and kit_name != app_state.LAST_PALETTE_KIT:
+        app_state.save_last_palette_kit(kit_name)
     types = palette.list_component_types(kit_name)
 
     for type_name, base in types:
@@ -3024,9 +3026,13 @@ def refresh_palette_kits():
         palette_kit_var.set("")
         return
 
-    palette_status.config(text=f"{len(palette_kit_names)} kits")
-    palette_kit_var.set("")
-    fit_tree_column(palette_tree)
+    # Reopen the kit chosen last so the palette is never left empty; a file without that
+    # kit opens on its first kit instead, without forgetting the remembered one.
+    if app_state.LAST_PALETTE_KIT in palette_kit_names:
+        palette_kit_combo.current(palette_kit_names.index(app_state.LAST_PALETTE_KIT))
+    else:
+        palette_kit_combo.current(0)
+    populate_palette_types()