Re: [Update REQ 6867]: `Pause until key is pressed'

[munzner at cs.stanford.edu]

> But I have added a bit of background to the question.
> The set up is that I am giving the talk with `Magicpoint'.
> Magicpoint is a line based presentation package.

Thanks, the background is useful. 

> 1) Just break up the gcl files into  the relevant sections, and having
> in the magicpoint file:
> %system "geomview ... filePart 1"
> %pause     (which is a command to magicpoint to stop until a key is
> pressed)
> %system "geomview ... filePart 2"
> 
> The disadvantage of this is the nasty flicker caused by opening and
> closing the geomview camera windows. This is particularly pronounced
> because geomview, by default, opens the camera window in the `wrong'
> place. (I can not get the -wpos option working.)

I see your point about the flicker problem. I have a vague memory that
the problem with wpos being ignored is a known bug in the Linux
version.

> 2) I thought I could add a `shell (read n)' command to the gcl file at the
> point where I want a pause. This, I imagined, would mean execution
> gcl file would stop until something was typed in. But in fact the camera
> window
> goes grey and everthing grinds to a halt!
> -I dont much (anything?!) about command shells etc. I dont know what
> going on here...

Hmm. I'm not totally clear on what happened, but I'm pretty sure it's
geomview not finding input (to pass through to the shell) in the
expected place. If I start geomview from the command line in a
terminal window, feed a gcl file with that line into geomview and then
type something in that terminal window, it works as expected. But since
you started geomview from the magicpoint thing I don't think you have
a place to type that input and geomview would just stay frozen and
waiting forever.

But anyway, it's a moot point. Option 3 below is the way to go, it was
written exactly so that people don't have to mess around with shells
and pipes.

> 3) In the man pages for geomview I noticed the geomview -M option
> and the `togeomview' command. This, it seems, might give a better
> version to solution 1). -I should have lines:
> 
> %system "geomview -M filePart 1"  (loads the objects and does something)
> %Pause    (wait until key presses)
> %system "togeomview filePart 2"  (send geomview more gcl commands to the
> object
> s already in the camera window)

Very close. In this case "togeomview" is the right way to go. But two
things - first, just use "togeomview" everywhere, even that first
time. It will automatically figure out that it needs to start a new
copy of geomview if there isn't one running. Second, you need to feed
it the files as standard input, so you need a "<" before the filename.
So your example above would look like this:

%system "togeomview < filePart1"
%Pause
%system "togeomview < filepart2"
etc.

> --But I cant sort this out! All this stuff about pipes... ho hum.

The whole idea of togeomview is that you don't have to understand much 
about pipes in order to use it - it's making the pipes for you, behind 
the scenes.

The only possible problem here could be the bug in togeomview that got
fixed in version 1.6.1p8. It might not be a problem for you - if you
run it, and things work, then you're all set. If you get errors like

 Couldn't exec geomview nor gv: Bad address
 Couldn't start geomview

then the bug is relevant, and you should grab

 ftp://ftp.geom.umn.edu/priv/slevy/togeomview.linux

which should work. 

 Tamara