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From: osborn@ux1.lbl.gov (James R Osborn)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Drawing direct to a dialog window...
Message-ID: <13295@dog.ee.lbl.gov>
Date: 16 May 91 18:58:03 GMT
References: <1991May15.131300.9898@umiami.ir.miami.edu> <1991May16.170121.7022@oceania.UUCP>
Reply-To: osborn@ux1.lbl.gov (James R Osborn)
Organization: Lawrence Berkeley Laboratory
Lines: 55
X-Local-Date: Thu, 16 May 91 11:58:03 PDT


I have gotten some flack for liking the Dialog Manager and more
specifically liking to abuse it!  I find that it is much easier
to install a userItem to do updating for specific drawing tasks
than using a filter procedure and doing the updating myself.

I like this because usually you don't need to write a filter proc.
So why add one just to do updating in a dialog when a mechanism
(the userItem) is provided for you?  Another nice thing is that
you can reuse the same userItem procedure for a series of different
items.  Just use a switch inside the draw procedure to select which
item to draw.  And you can use the same draw procedure to draw the
same item all over your dialog.  You just set the rectangle different
for each item, then in your draw procedure, you retrieve the item
rectangle for the item you are drawing (using GetDItem).

One other interesting thing.  If you use a dialog (instead of a window)
that has userItem(s) installed to do your updating, then your window
will get updated *BEHIND* a modal dialog that you put up.

Try this:

1) go to the finder
2) make sure a folder or disk window is open
3) go to the File menu and choose Page Setup...
4) You get a modal dialog in front of the Finder's windows
5) Now activate your favorite screen saver so that the entire screen
   goes black or whatever causing the screen to need updating

You will notice that the modal dialog will update since it's internal
event loop is in control.  The Finder's windows (which presumably are
not dialog windows) do not get updated until you Cancel/OK out of the
modal dialog.

This is annoying.  For example when printing a long document in the
foreground.  A modal print dialog comes up and tells you the status.
If your screen saver kicks in, then when the screen is redrawn, any
documents you have open won't update until you finish printing.  If
a modeless dialog was used for the document window with userItems to
cause text updating, then the documents would be updated properly by
the dialog manager.  I think this is real neat.  It keeps your screen
looking good after a screen saver has erased everything.  Unfortunately,
I think using the dialog manager to do all event processing for an
application's documents is considered dialog manager abuse (by the
powers that be).

Sorry for all the hot air  :^o
-- james

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