Subject: Re: Re: FVWM: TODO List comment

From: Tim Phipps <[email-masked]>
Date: Tue, 7 May 1996 11:13:15 +0100

> 
> Anyway, I think my explanation of why the frame window gets cleared to the
> background colour of the frame still stands.  Only, I guess we've just proved
> that you cannot do anything about it, so presumably it could be taken off the
> TODO list.  (I'm trying to save you some work here Chuck  ;-)
> 
What I think is happening is that the X-server is painting the frame
with it's background colour when the client window disappears.  I haven't
looked at the window frame creation code but I suspect from these symptoms that
it is given a background colour in order to speed up refreshes (only the
non-background bits need to be drawn by fvwm).

Since fvwm can't stop clients unmapping themselves and can't stop the server
filling in the background colour when the frame centre is exposed the only
way to stop the flashing is to make sure the area under the client window
has a background of none.

There are two ways to do this, either don't set the frame background and live
with the extra drawing overhead or create an intermediate window with no
background under the client but above the frame.

When there is no background for the server to paint the screen will be left
with the contents of the client window until the frame is unmapped.

Hope this helps,
Tim Phipps.
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---

From: [email-masked]
Date: Tue, 7 May 96 11:45:29 +0100

> non-background bits need to be drawn by fvwm).

Yup, that's exactly what I was thinking.

> with the contents of the client window until the frame is unmapped.

Nifty.  Yes, I think this might just work.  I guess the only disadvantage is if
the window manager or comms lock up straight after the client exits, in which
case, the user will be left with a client that looks OK, but doesn't respond at
all.  But, then that's no bad thing really, because whatever you do to it, it
won't cause any problems.

My vote would be for the extra window.  I know that adds a lot of extra windows
(one per client window), but we are not trying to solve the problem for fast
machines.  The situation that needs resolving is the one where the
machine/network is slow, in which case we NEED the background colour to minimise
repainting work, but we also need the extra window with background colour none
to avoid the flash.

> Tim Phipps.

Well done !  Nice bit of round-about thinking.

  Cheers,
    Jonathan.