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Date: Thu, 7 Feb 2013 17:25:31 +1100
Subject: Re: Monitoring updating directory for image for GUI
From: Chris Angelico <rosuav@gmail.com>
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Xref: csiph.com comp.lang.python:38333

On Thu, Feb 7, 2013 at 9:02 AM,  <ciscorucinski@gmail.com> wrote:
> Basically I am creating a program that will stream musical notes into a p=
rogram called Lilypond one-by-one and it will create the sheet music for th=
at stream of music via OS command. Your understanding of Lilypond is not ne=
eded, but you need to know that for each new note that is streamed in "real=
-time", a PNG image file will be created for that stream of music up to tha=
t point...via Lilypond.

I'm surprised nobody has yet responded to this. The list's usually a
lot quicker, heh...

Side point: How real-time can you actually run Lilypond? It usually
takes a bit of time to render a sheet of music. But leaving that
aside.

> What I am looking at doing is to monitor the directory where the image fi=
les are being created in real-time, and update the GUI (build with gtk.Buil=
der and Glade) with the most recent image file. I have the program multithr=
eaded and it appears that all of the images are being created sequentially;=
 however, I need to make sure that an older image (an image with less notes=
 displayed) is NOT going to be displayed over a newer image.
>
> The question I have is what do you see as the best way of going about thi=
s?

Not sure I fully understand the problem here. Tell me if this workflow
is correct:

* Note comes in
* Lilypond is spawned asynchronously to render the new state
* A new file is created, with a unique name
* Your program shows the latest of these files, no more and no less

Or do you need to sometimes show multiple files?

Can you make use of sequential file naming to ensure that you can
always find the latest file? That way, you just make sure you never
overwrite a displayed image whose name is > than the one you now have.

ChrisA