On Thu, May 31, 2012 at 3:42 AM, Terry Reedy <tjre...@udel.edu> wrote: > On 5/30/2012 6:19 PM, Matteo Landi wrote: >> >> On May/28, Matteo Landi wrote: >>> >>> Hi list, >>> recently I started to work on an application [1] which makes use of the >>> Tkinter >>> module to handle interaction with the user. Simply put, the app is a >>> text >>> widget displaying a file filtered by given criteria, with a handy feature >>> that >>> the window is raised each time a new line is added to the widget. >>> >>> The application mainly consists of three threads: the first one, the >>> file >>> processor, reads the file, filters the lines of interest, and pushes them >>> into >>> a shared queue (henceforth `lines_queue`); the second one, the >>> gui_updater, >>> pops elements from `lines_queue`, and schedule GUI updates using the >>> `after_idle` method of the Tkinter module; finally the last one, the >>> worker >>> spawner, receives commands by the gui (by means of a shared queue, >>> `filters_queue`), and drives the application, terminating or spawning new >>> threads. >>> >>> For example, let's see what happens when you start the application, fill >>> the >>> filter entry and press Enter button: >>> 1 the associated even handler is scheduled (we should be inside the >>> Tkinter >>> mainloop thread), and the filter is pushed into `filters_queue`; >>> 2 the worker spawner receives the new filter, terminate a possibly >>> running >>> working thread, and once done, create a new file processor; >>> 3 the file processor actually processes the file and fills the >>> `lines_queue` >>> with the lines matching given filter; >>> 4 the gui updater schedules GUI updates as soon as items are pushed into >>> `lines_queue` >>> 5 Tkinter mainloop thread updates the gui when idle >>> >>> What happens when the main window is closed? Here is how I implemented >>> the >>> graceful shutdown of the app: >>> 1 a quit event is scheduled and a _special_ message is pushed into both >>> `filter_queue` and `lines_queue` >>> 2 the gui updater threads receives the _special_ message, and terminates >>> 3 the worker spawner receives the message, terminates the working thread >>> and >>> interrupts her execution. >>> 4 Tk.quit() is called after the quit event handler, and we finally quit >>> the >>> mainloop >>> >>> Honestly speaking, I see no issues with the algorithm presented above; >>> however, >>> if I close the window in the middle of updates of the text widget, the >>> applications hangs indefinitely. On the other hand, everything works as >>> expected if I close the app when the file processor, for example, is >>> waiting for >>> new content to filter. >>> >>> I put some logging messages to analyze the deadlock (?!), and noticed >>> that both >>> the worker spawner and the file processor are terminated correctly. The >>> only >>> thread still active for some strange reasons, is the gui updater. >>> >>> Do you see anything wrong with the description presented above? Please >>> say so, >>> because I can't figure it out! > > > Since no-one else answered, I will ask some questions based on little > tkinter experience, no thread experience, and a bit of python-list reading. > > 1. Are you only using tkinter in one thread? (It seems like so from the > above)?
Yes, provided that `after_idle` queues a job for the gui thread > > 2. Is root.destroy getting called, as in 24.1.2.2. A Simple Hello World > Program in the most recent docs? (I specify 'most recent' because that > example has been recently revised because the previous version sometimes > left tkinter hanging for one of the code paths, perhaps similar to what you > describe. No, I'm not calling the destroy method of the main window but, why that only happens while doing gui updates? > > 3. Have you tried making the gui thread the master thread? (I somehow expect > that the gui thread should be the last to shut down.) No but, same question as above. I'm not home right now, so I will try those solutions as soon as possible. Thanks. Cheers, Matteo > > -- > Terry Jan Reedy > > -- > http://mail.python.org/mailman/listinfo/python-list -- http://www.matteolandi.net/ -- http://mail.python.org/mailman/listinfo/python-list
