Module single_instance 

One tray UI per config directory.

ui holds <config dir>/ui.lock exclusively for its whole life; the OS releases it when the process exits, however it exits. A second ui for the same config finds the lock taken, leaves a raise request (ui.raise) for the running one and exits, so a config never gets two tray icons. The running UI watches for the request and shows its window.

Structs

UiLock

The held UI lock; dropping it releases the lock.

Enums

Instance

The outcome of acquire.

Constants

LOCK_FILE_NAME

The UI lock’s file name, next to config.toml.

RAISE_FILE_NAME

A second launch’s request to show the running UI’s window.

RAISE_POLL

How often the running UI looks for a raise request.

RESTART_ATTEMPTS

How long a UI restarting itself for the display waits for the lock its predecessor still holds: attempts × pause = 5 s.

RESTART_PAUSE

Functions

acquire

Take the UI lock for the config at config_path, trying attempts times pause apart. A stale raise request is dropped once the lock is ours, so it cannot pop the window open later.

hand_over

Ask the running tray UI to show its window, and say so.

lock_path_for

The UI lock for the config at config_path.

raise_path_for

The raise request for the config at config_path.

take_raise_request

Consume a pending raise request; answers whether there was one.

watch

Until stop, consume raise requests and call raise for each, when it can (raise answers whether the window could be reached).