Path: utzoo!attcan!utgpu!watmath!iuvax!uxc.cso.uiuc.edu!news
From: dorner@pequod.cso.uiuc.edu (Steve Dorner)
Newsgroups: comp.sys.next
Subject: Re: Browser auto-update
Message-ID: <1989Aug15.150743.12979@uxc.cso.uiuc.edu>
Date: 15 Aug 89 15:07:43 GMT
References: <7324@microsoft.UUCP> <800018@mrcnext.cso.uiuc.edu>
Reply-To: dorner@pequod.cso.uiuc.edu (Steve Dorner)
Organization: University of Illinois at Urbana-Champaign
Lines: 41

In article <800018@mrcnext.cso.uiuc.edu> carlson@mrcnext.cso.uiuc.edu writes:
>...
>1. Have EVERY Unix program send an UPDATE message to the window
>...
>2. Change the kernal so that _it_ sends an UPDATE message to 
>...
>Clearly, any method to notify processes of filesystem changes
>is going to be messy and consume CPU cycles.  I belive that Multifinder 
>on the Mac sort of does this.  Does anyone know the details?

All this talk about patching the kernel or libraries is, as someone
mentioned, over the line. I really think this issue is much simpler
than all this. First, let me make a guess:

GUESS:  Both the NeXT browser and the Mac Finder notice when files have
been created or destroyed by POLLING THE MODIFY TIME of the directories
they display; every n seconds, they look at the modify time on any
displayed directory.

The Finder then displays (or removes) any file name or icon that has
been created (or destroyed). The Browser just changes its title.

I stick by my suggestion to add a default to the Browser that, if set
by the user, would make the browser update its views when its normal
polling behavior detects a change. CPU cost? To those of you who leave
it turned off, enough cycles to check a flag once every n seconds,
given that the Browser is already doing stat calls every n seconds
anyway. To those of us who turn it on, however long it takes to update
the Browser, when the Browser is running and notices a change in one of
its displayed directories.

I realize that there are changes to files that do not involve changing
the modify times on directories, such as file size changes.  The
macintosh Finder ignores these, and I don't think that's a bad policy;
after all, the important thing is that the darn files show up and can
be manipulated.

-- 
Steve Dorner, U of Illinois Computing Services Office
Internet: s-dorner@uiuc.edu  UUCP: {convex,uunet}!uiucuxc!dorner
IfUMust:  (217) 244-1765