Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!caip!rutgers!lll-crg!lll-lcc!styx!twg-ap!amdahl!pyramid!prls!philabs!mcnc!rti-sel!sas!toebes
From: toebes@sas.UUCP (John Toebes)
Newsgroups: net.micro.amiga
Subject: Re: Making a screen invisible
Message-ID: <205@sas.UUCP>
Date: Fri, 17-Oct-86 09:56:10 EDT
Article-I.D.: sas.205
Posted: Fri Oct 17 09:56:10 1986
Date-Received: Tue, 21-Oct-86 21:08:46 EDT
References: <776@oswego.UUCP>
Organization: SAS Institute Inc. Cary, NC
Lines: 36
Summary: POPCLI does exactly what you want.

In article <776@oswego.UUCP> pacs4900@oswego.UUCP (Mark Reichert) writes:
>Does anyone know how to make a screen not be displayed?. . .[I] would just as
>soon not have my cycles stolen while the program is running. . .

POPCLI does exactly this when it shuts down the screen.  It first opens a small
screen in lores with a black background.  It then shuts down the DISPLAY with
the OFF_DISPLAY macro.  The sources were posted to mod.amiga about a week ago.
The basic code is:

#include <graphics/gfxmacros.h>
#include <hardware/custom.h>
#include <hardware/dmabits.h>
...
extern struct Custom custom;
struct NewScreen      NewScreen = 
   { 0, 0, 320, 30, 1, 0, 1, NULL, CUSTOMSCREEN, NULL, NULL, NULL, NULL };
extern struct Screen   *OpenScreen(), *myscreen;

   if ((myscreen = OpenScreen(screen)) != NULL)
      {
      /* set the background color to black.  this is the color that is */
      /* displayed when the display is turned off */
      SetRGB4(&(global.blankscreen->ViewPort), 0, 0, 0, 0);
      /* turn off the display - this gives cycles back to the 68000 AND sets */
      /* the screen to the current background color */
      OFF_DISPLAY

      (void) CloseScreen(global.blankscreen);
      ON_DISPLAY
      }

Note that opening the separate screen is a convenience on my part.  It is
easier than having to locate, save and restore the current background color.
-- 
John A. Toebes, VIII       usenet:..mcnc!rti-sel!sas!toebes
USnail: 235 Trillingham Ln, Cary NC 27511   BBS:(919)471-6436