display vs video sync vs ^L

[Brian K. White]

I was just playing with using a interactive program as the argument to a 
printer ommand in processing.
After getting the script to capture stdin to a temp file and dealing with 
some difficulties with the tty, I got it working and it greatly simplifies 
the use of our destprint util.

Normally where you might say
Then: printer "lp -d someplace"
or
Then: printer "mail -s \"some subject\"" < mailaddr
etc...

I'm putting
Then: printer "destpr"
where destpr is a script that captures stdin to a temp file and then runs an 
rclerk process
rclerk .... -r $tempfile <$tty


This allows me to greatly simplify the use of that printer utility.
Previousy the process looked roughly like this anywhere you wanted to print:

tmpfile = long concatenation of things to make an informative and unique 
file name...
system "umask 0:>"<tmpfile
printer file tmpfile
form "someform"
printer flush ; printer reset
system "destpr " < tmpfile
x = remove(tmpfile)

now all I need is:

printer "destpr"
form "someform"
printer reset


Except... upon returning from the printer command, the screen is left mostly 
blank except for the bottom of the screen prompts.
I tried putting both display and video sync after the printer reset to no 
effect.
I noticed that pressing Ctrl-L does refresh the screen.
I failed to find a definitive list of special codes understuud by pushkey to 
try and push a Ctrl-L from within filepro.
I finally figured out pushkey "[DRAW]"  by doing "strings rclerk |less", 
and then searching for a code I did know like BRKY, and luckily that panned 
out and there was a nice list in there, and luckily, the pushkey actually 
did cause a refresh like Ctrl-L.
(I was prepared to find that ctrl-l worked at the os or shell level as part 
of the tty line discipline and stty settings, and that
trying to pushkey from inside fp wouldn't have the desired effect, that it 
needs to come from the terminal for real, happy surprise it actually works)

My question is, is that really the only way to get the screen to redraw?
I never like relying on pushkeys. Just seems too Rube Goldberg.
The descriptions for display and video sync both say they will redraw the 
screen, why don't they?
Btw this is @key processing so a screen command isn't indicated.
Besides, I tried that and the screen stayed blank. It went into update mode 
because the cursor went to the place on the screen where the first field 
would be if it were visible.

Also, it would be super duper if there was some way to control how a sub 
process like a printer command gets run.
In this case, after getting all this working, I think I really can't use it 
anyways because:

The sub process is getting run as user filepro.
This, (or something) causes the rclerk process to be unable to read or write 
the tty the user is on.
I have made it work though by putting chmod 666 $tty in /etc/profile.local
I don't want to do that for real though because I really don't want root's 
tty's to be world writeable!
I could exclude root from that command, or maybe use 660 which might allow 
all users to work as long as users and filepro are all in the same group, 
but then the process woudn't work for root and I can't use this unless it 
works both for root and users equally.

PFSYSEUID had no effect on this either way.

Maybe PFPOSTPRINT is a possible workaround, I haven't tried that yet, but 
it's only useful if it can be selectively applied and revoked like a printer 
command. I can't have it just in the env all the time, or even all during a 
given clerk session.

Brian K. White  --  brian at aljex.com  --  http://www.aljex.com/bkw/
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