Path: utzoo!attcan!uunet!munnari.oz.au!metro!research.canon.oz.au!andy
From: andy@research.canon.oz.au (Andy Newman)
Newsgroups: comp.windows.x
Subject: Locking Areas of the (physical) Display.
Message-ID: <1990Oct28.223626.1319@research.canon.oz.au>
Date: 28 Oct 90 22:36:26 GMT
Reply-To: andy@research.canon.oz.au (Andy Newman)
Organization: Canon Information Systems Research Australia
Lines: 36

I have a rather interesting problem with integrating a piece of
hardware with an X-based application and was wondering if any
kind soul(s) on the net have any ideas or could at least point
me in the right direction (and its not my homework :-)).

The application is based on the MOTIF widgets and runs under
mwm running on the MIT R4 X server using a memory mapped
framebuffer, nothing special here. Now for the fun stuff...

I have some hardware that writes directly to the framebuffer
memory, this hardware is controlled from the application. The
hardware can write anywhere on the display so directing it to
the area of the screen containing the application's window is
not a problem.

The problem arises from having the user move the window while
my hardware is writing to display memory or having another
client map a window over the area being written, or any other
modifications to the display area in which the hardware is
writing.

How can I ensure that the display (the area of it that the
hardware is writing to) is not disturbed while my hardware is
operating? I can't stop the hardware doing its stuff (which
can take a few seconds) and I don't want a messy looking
display with other client's windows being clobbered by my
hardware's modifications to the framebuffer. I also don't want
to interfere with the normal operations of the system too
much (e.g. the second hand on the clock keeps spinning while
the hardware works away).

Any help would be much appreciated.
-- 
Andrew Newman, Software Engineer.            | Net:   andy@research.canon.oz.au
Canon Information Systems Research Australia | Phone: +1 61 2 805 2914
P.O. Box 313 North Ryde, NSW, Australia 2113 | Fax:   +1 61 2 805 2929