[C] Fix unwanted point moveage in VM

[Aidan Kehoe]

 Ar an naoú lá déag de mí Méan Fómhair, scríobh Julian Bradfield: 

 > In article <18149.58079.498563.234436 at puma.r.npc.de> Joachim Schrod <jschrod at acm.org> writes:
 > >>>>>> "MS" == Michael Sperber <sperber at informatik.uni-tuebingen.de> writes:
 > >MS> So before I sink more work into this: Can you confirm that the
 > >MS> "flicker" problem seen on 21.5 also occurs with the new VM?
 > >
 > >I don't know if I fully understood what Julian's "flicker" problem
 > >is actually... Thus, let me rephrase the situation as I observe it.
 > >
 > >When one moves from one message to another (i.e., evaluates
 > >#'vm-next-message), the frame goes completely white and is then
 > >rebuild. Is that the "flicker" problem of Julian? This is the same in
 > >VM 7.17/7.19 and VM 8.0. I'd think that this behaviour was already
 > >there when I still used XEmacs 21.4; I don't remember any change here. 
 > >AFAIU, that's done during the construction of the mail's presentation
 > >(MIME decoding and so).

It should be possible to avoid this in VM. AIUI it’s a result of doing
coding system and base64, quoted-printable decoding on displayed text, which
will always cause a redisplay flash if the relevant text is being shown. 
(Text is inserted, more text is deleted). It would make more sense to
do all the decoding somewhere that’s not being redisplayed, and only show
the text when the decoding is finished. 

I’ve tried this a couple of times--I see the problem too, but its not as
much of an issue on the TTY builds I normally use, of course--but I haven’t
had much traction, unfortunately. 

 > Yes, I guess that's what I mean. On 21.5, it is very visible, and very
 > annoying - even on a tty frame, even on a very fast machine. On 21.4,
 > it's not visible at all on any machine I use, as far as I can see, so
 > I don't know whether it even happens.
 > I suppose I could put them under xscope to see what's actually
 > happening to the window!

-- 
On the quay of the little Black Sea port, where the rescued pair came once
more into contact with civilization, Dobrinton was bitten by a dog which was
assumed to be mad, though it may only have been indiscriminating. (Saki)