Path: utzoo!utgpu!news-server.csri.toronto.edu!torsqnt!jtsv16!blister!canrem![len.turner@canrem.uucp]
From: "len turner" <len.turner@canrem.uucp>
Newsgroups: comp.sys.amiga.programmer
Subject: filehandle for screen
Message-ID: <1991Jun2.848.3626@canrem.uucp>
Date: 2 Jun 91 15:10:39 EST
Reply-To: "len turner" <len.turner@canrem.uucp>
Distribution: comp
Organization: Canada Remote Systems

  
 On 06-01-91 at 12:09 John Russel replied:

JR>(Under KS 1.3) When a custom screen is in front of the WB screen, and
JR>its flag bits contain the value WBSCREEN, any window that tries to open
JR>on WB opens on the custom screen instead.  Nothing special about the

  How system friendly is this?  If I do something like:

     twiddle bits to make my screen WB;
     Execute("pgm-name",NULL,NULL);
     untwiddle the bits I twiddled before

then during the time that other program is running, my screen _is_ the WB
screen.  Unfortunately, since the Amiga multi-tasks, there may be another app
running that decides this would be a good time to open a window on the
workbench.  Would not that window end up on my screen?

  This seems to make it all too possible for my app to exit, closing its
screen, while someone else's window is still open on it.  I suspect this
would not have a pleasing effect on the user.

  Is there a safe way to get around this?

  I could reduce the time when that could happen by using 
     Execute("run pgm-name", NULL,NULL);
but for the purposes of my app I want the other program to be run
synchronously.  Other wise the user would have an opportunity to muck things
up himself. ("never underestimate the stupidity of an end user.").

JR>filehandle.  Note that the flag bits are only part of a word, so you

  I managed to mix two separate questions together.  The need for a
filehandle arises when my app has been called from WB, so has no stdin or
stdout and I need to use a routine that only runs from CLI and confidently
expects to find valid stdin & stdout (or at very least stdout).

  In some cases at least I could use something like

BPTR hndl=Open("NIL:",MODE_OLDFILE);
  if(hndl!=NULL) Execute("pgm-name",hndl, hndl);
  else {do something intelligent about the situation}

but I don't know if that would be safe in general.

JR>can't just assign WBSCREEN, you have to use a combination of and/or
JR>operations.

JR>(Under KS 2.0) I understand there is a system-supported way of doing it,
JR>but don't know details.

  I don't have 2.0 on my 500, and considering the current state of my
finances it may be quite a while after it becomes available that I do get
it.  Consequently, information about how easy this would be under 2.0 is not
only not very helpful, it's downright depressing.  :-(

Thanks for the quick reply & help.

--Len

len.turner@canrem.uucp (len.turner%canrem.uucp@lsuc.on.ca)
...lsuc!canrem!len.turner

---
 # Amy Reads Her Mail v0.77 # (ALPHA)
--
Canada Remote Systems.  Toronto, Ontario
NorthAmeriNet Host