Add tkinter.systray.NotificationHandler — a logging handler which shows log records as desktop notifications

Feature or enhancement

The tkinter.systray module (gh-153259) wraps the tk sysnotify command in the notify() function. A natural application of desktop notifications is showing warnings and errors reported via the logging module: a GUI application usually has no console, and a message box for every error is too intrusive.

I propose to add the NotificationHandler class to tkinter.systray. It formats the record with the handler's formatter and sends it as a notification. The title of the notification is the title argument, or the level name of the record (e.g. WARNING) by default. The master argument is the Tk window used to send notifications; by default the default root window is looked up when a record is emitted, so the handler can be created before the root window. Failures are reported via handleError(), as usual for logging handlers.

import logging
import tkinter
from tkinter.systray import NotificationHandler

root = tkinter.Tk()
handler = NotificationHandler('My application')
handler.setLevel(logging.WARNING)
logging.getLogger().addHandler(handler)

The handler belongs to tkinter.systray rather than logging.handlers because it is specific to Tk applications: it needs a Tk root window and follows tkinter's rules for the default root and for calls from other threads. logging.handlers should not depend on an optional GUI package.

Linked PRs

• gh-157760

Start with the existing tkinter.systray module and its notify() function, then inspect linked PR gh-157760 before doing any work. The requested result is a NotificationHandler that formats records, uses the title or level name, resolves the Tk master as described, and reports failures through handleError(); no test file is named.