Connect to another device without disconnecting first

Connect and Discover stay enabled while a device is connected. Pressing
Connect in the dialog drops the current device before the new one is
tried; cancelling the dialog leaves the connection alone.

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 = "0.0.0.139"
+VERSION = "0.0.0.141"
 PROPERTIES_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)), "editor.properties")
 DEFAULT_GRID_SIZE = 10
 DEFAULT_ADD_TIMESTAMP = True

connect_dialog.py

@@ -21,8 +21,9 @@ import app_state
 class ConnectDialog:
     """Modal dialog for entering device connection parameters."""
 
-    def __init__(self, parent, on_connect_callback):
+    def __init__(self, parent, on_connect_callback, on_before_connect=None):
         self._callback = on_connect_callback
+        self._before_connect = on_before_connect
         self._thread = None
         self._cancelled = False
 
@@ -103,6 +104,11 @@ class ConnectDialog:
             self._status_label.config(text="Invalid port number", foreground="#c00000")
             return
 
+        # Runs here, on the main thread, rather than in the worker: it is where a
+        # device already connected is let go, and that takes the UI down with it.
+        if self._before_connect is not None:
+            self._before_connect()
+
         self._btn_connect.config(state="disabled")
         self._status_label.config(text="Connecting...", foreground="#666666")
 
@@ -169,9 +175,10 @@ class DiscoverDialog:
     """Modal dialog that broadcasts DASP DISCOVER, lists responding
     devices, and lets the user pick one to connect to."""
 
-    def __init__(self, parent, on_connect_callback):
+    def __init__(self, parent, on_connect_callback, on_before_connect=None):
         self._parent = parent
         self._callback = on_connect_callback
+        self._before_connect = on_before_connect
         self._discover_thread = None
 
         self._dlg = tk.Toplevel(parent)
@@ -318,7 +325,7 @@ class DiscoverDialog:
         host = values[0]
         port = self._port_var.get().strip()
         self._dlg.destroy()
-        _CredentialsDialog(self._parent, self._callback, host, port)
+        _CredentialsDialog(self._parent, self._callback, host, port, self._before_connect)
 
 
 # ────────────────────────────────────────────────────────────────────
@@ -328,8 +335,9 @@ class DiscoverDialog:
 class _CredentialsDialog:
     """Small modal that asks for username and password, then connects."""
 
-    def __init__(self, parent, on_connect_callback, host, port):
+    def __init__(self, parent, on_connect_callback, host, port, on_before_connect=None):
         self._callback = on_connect_callback
+        self._before_connect = on_before_connect
         self._host = host
         self._port = port
         self._thread = None
@@ -397,6 +405,11 @@ class _CredentialsDialog:
             self._status_label.config(text="Invalid port", foreground="#c00000")
             return
 
+        # Runs here, on the main thread, rather than in the worker: it is where a
+        # device already connected is let go, and that takes the UI down with it.
+        if self._before_connect is not None:
+            self._before_connect()
+
         self._btn_connect.config(state="disabled")
         self._status_label.config(text="Connecting...", foreground="#666666")
 

main.py

@@ -2316,7 +2316,8 @@ def do_device_connect():
         wiresheet.render_components([])
         app_state.window.title(app_state.base_window_title())
 
-    connect_dialog.ConnectDialog(app_state.window, _connect_to_device)
+    connect_dialog.ConnectDialog(app_state.window, _connect_to_device,
+                                 on_before_connect=_drop_device_before_connect)
 
 
 def do_device_discover():
@@ -2337,7 +2338,18 @@ def do_device_discover():
         wiresheet.render_components([])
         app_state.window.title(app_state.base_window_title())
 
-    connect_dialog.DiscoverDialog(app_state.window, _connect_to_device)
+    connect_dialog.DiscoverDialog(app_state.window, _connect_to_device,
+                                  on_before_connect=_drop_device_before_connect)
+
+
+def _drop_device_before_connect():
+    """One device at a time: the one already connected goes before the next is tried.
+
+    Called when Connect is pressed, not when the dialog opens, so backing out of the
+    dialog leaves the current connection alone.
+    """
+    if app_state.device_session is not None:
+        do_device_disconnect()
 
 
 def _connect_to_device(host, port, user, password):
@@ -2358,8 +2370,6 @@ def _connect_to_device(host, port, user, password):
 def _on_connected(ds, root_comp):
     """Main-thread callback after successful connect."""
     app_state.window.title(app_state.base_window_title_live())
-    menu_device.entryconfig("Connect...", state="disabled")
-    menu_device.entryconfig("Discover...", state="disabled")
     menu_device.entryconfig("Disconnect", state="normal")
     menu_device.entryconfig("Download to SAX...", state="normal")
     app_state.set_status(f"Connected to {app_state.device_host}:{app_state.device_port}")
@@ -2435,6 +2445,30 @@ def do_device_disconnect():
     wiresheet.render_components([])
 
 
+def quit_app():
+    """File > Exit and the window's close box: let go of the device before going.
+
+    Leaving without a proper close keeps the device's Sox session and subscriptions
+    alive until it times them out, so the next connect may be turned away.
+    """
+    global _cov_poll_id
+
+    if _cov_poll_id is not None:
+        app_state.window.after_cancel(_cov_poll_id)
+        _cov_poll_id = None
+
+    ds = app_state.device_session
+    app_state.device_session = None
+    app_state.live_mode = False
+    if ds is not None:
+        try:
+            ds.disconnect()
+        except Exception:
+            pass
+
+    app_state.window.destroy()
+
+
 def _start_cov_polling():
     """Starts the 100ms COV event polling loop on the main thread."""
     global _cov_poll_id
@@ -2616,7 +2650,7 @@ menu_file.add_command(label="Save As...", command=sax_file.save_file_as)
 menu_file.add_separator()
 menu_file.add_command(label="Print...", command=wiresheet.print_sheet, accelerator=f"{accel_mod}+P")
 menu_file.add_separator()
-menu_file.add_command(label="Exit", command=window.quit)
+menu_file.add_command(label="Exit", command=quit_app)
 menu_bar.add_cascade(label="File", menu=menu_file)
 
 menu_edit = tk.Menu(menu_bar, tearoff=0)
@@ -3000,6 +3034,8 @@ paned_window.add(frame_editor, weight=3)
 app_state.dirty_display_callback = refresh_dirty_display
 undo.set_refresh_callback(refresh_all_views)
 sax_file.set_tree_filled_callback(on_tree_filled)
+sax_file.set_disconnect_device_callback(do_device_disconnect)
+window.protocol("WM_DELETE_WINDOW", quit_app)
 refresh_palette_kits()
 apply_left_pane_width()
 

sax_file.py

@@ -31,6 +31,15 @@ def set_tree_filled_callback(callback):
     _tree_filled = callback
 
 
+_disconnect_device = None
+
+
+def set_disconnect_device_callback(callback):
+    """Registers how to drop the live device session before a file takes its place."""
+    global _disconnect_device
+    _disconnect_device = callback
+
+
 def parse_xml_to_tree(treeview, parent_node, xml_element):
     """Recursively traverses XML elements and adds <comp> tags to the Treeview."""
     for child in xml_element:
@@ -132,19 +141,6 @@ def open_file():
         messagebox.showwarning("Action Blocked", "Cannot load SAX profiles because 'Sedona home folder' configuration is missing or empty.")
         return
 
-    if app_state.live_mode:
-        answer = messagebox.askyesnocancel(
-            "Device Connected",
-            "A live device connection is active.\n\n"
-            "Disconnect from the device and open a file?\n\n"
-            "Choose Yes to disconnect and open, No to cancel.",
-        )
-        if not answer:
-            return
-        # Import here to avoid circular import at module level
-        from main import do_device_disconnect
-        do_device_disconnect()
-
     file_path = filedialog.askopenfilename(
         title="Select SAX File",
         filetypes=[("SAX Files", "*.sax"), ("XML Files", "*.xml"), ("All Files", "*.*")],
@@ -152,6 +148,11 @@ def open_file():
     if not file_path:
         return
 
+    # A session is a file or a device, never both. The device goes only once a file has
+    # actually been chosen, so cancelling the dialog leaves the connection as it was.
+    if app_state.device_session is not None and _disconnect_device is not None:
+        _disconnect_device()
+
     canvas = app_state.canvas
     tree = app_state.tree