AutoBlack(tm) -- The screen saver with a light touch -- User Notes
Version 1.5
When AutoBlack is installed, after five minutes of user inactivity, the Mac
screen will go black to prevent burning an image of the desktop (or whatever is on the screen) into the phosphor of the CRT. Any user activity (move the mouse, press any key, insert a disk) will immediately restore the current contents of the screen display with no waiting for system "update events" to redraw it. The five minute timer restarts from the last time of user activity, and may be setby the user to any desired value.
As a special feature, there are two built-in variants on the delay time. If the mouse is pushed all the way into the top right-hand corner of the screen, the delay is reduced to about two seconds, regardless of the delay setting, so you can hide the screen in a hurry if you need to do that. Alternatively, if the mouse is pushed all the way into the bottomright-hand corner of the screen it takes a couple hours, so if you are passively watching computer output you don't need to alter the delay time nor keep moving the mouse every few minutes.
While the screen is turned off an analog clock icon is displayed at random positions, to show that the Mac is still turned on. The clock will show the correct time of day if the program running at that time has a normal Macintosh interface (that is, it is calling the SystemTask trap from time to time). Ifthe clock shows random times, changing every time it is drawn, it is becauseyou have not set the time and date correctly since you last removed the battery.
INSTALLATION
AutoBlack can be installed in any of three ways. Primarily it is designed to install itself in RAM on bootup. To do this requires that it be present in the system folder on your bootup disk. Alternatively, it can be double-clicked as an application from any folder. After it is installed, it is not needed on any disk drive, and it will continue to be active no matter what the Mac is doing, until you power off, Shut-down or press the Reset button.
The preferred method to install this program at bootup is to copy it to the system folder of your bootup disk and rename it "MacsBug". The operating system always loads in a file named "MacsBug" (if it is there) before it does anything else, and it is important that AutoBlack be loaded in first, before any RAMdisk or even MacsBug itself. If you need MacsBug to be loaded also, rename it "Disassembler" and it will be loaded in after AutoBlack. Next time you boot up, AutoBlack will install itself in RAM (but the bootup box will say "MacsBug installed").
AutoBlack is also configured to install as an INIT file. In this mode you can
name it anything you wish; System 3.2 and later versions will look for all INIT files like AutoBlack in the system folder and start them up as part of its boot procedure. If you have other INITs or the real MacsBug in the system folder, this may fail. If you have the 128K ROMs (that is, you are using a double-sided internal drive) the INITs are loaded in alphabetical order; you can just rename the other INITs so they come later in the alphabet. If AutoBlack is not able to install properly, a dialog will inform you of its failure. If the AutoBlack INIT file is named "MacsBug" it is guaranteed to install first, and you will see both the "MacsBug installed" message and a little notice put up by the INIT.
If other INITs, RAMdisks, or immortal desk accessories have not yet overwritten the memory required by AutoBlack, you can also run it as an application program. If you double-click on the AutoBlack icon from the Finder, you will normally get a message "An application cannot be found for this document." Hold the option and cloverleaf keys down while double-clicking to avoid this problem. Or you can use DeskZap, Fedit, or Resedit to change the file type to "APPL". This will result in a different icon (a Mac screen with the familiar hand in front of it); you can double-click this icon with no impediment.
You can run the application any time, even after AutoBlack is installed. It allows you to change the delay time from the default five minutes. Setting the delay time to zero disables AutoBlack, but you can always run the application again to start it back up with a new delay time.
My preference is to use AutoBlack in the APPL mode, name it "MacsBug", and leave it in the system folder. That way it always installs itself at bootup without requiring manual attention, but I can still easily double-click it to change the delay setting.
HOW IT WORKS
AutoBlack takes over the alternate display area and paints it black (except for the clock icon). Then a small task is installed in the vertical retrace queue of the Macintosh (when it also looks at the mouse and keyboard), which counts the time since the last user activity. Once the delay time is exceeded, the video hardware is switched to the alternate display. Any time user activity takes place, the display is switched back to the normal display area, and the timer is restarted. The Macintosh software is not told about the switch, so it continues to update the normal display area; thus the display is immediately current whenever the hardware is switched back. Programs continue to run normally even when the display is switched off, and their output will be there when you switch back. Programs that depend on the alternate screen may not work correctly, if at all.
Unlike other programs that load in at bootup time, it is essential that AutoBlack be first to load -- even before the debugger -- to get access to the alternate screen. INIT files other than AutoBlack often take part of the memory used by the alternate screen; if they get there first, AutoBlack cannot install itself. If it fails to load as an INIT, simply rename it "MacsBug" and try again. Some systems, notably the HyperDrive 2000, rejuggle the memory hardware at INIT time; there is no way for AutoBlack to install at the proper time in such a wierd system. Some INITs leave a lot of trash in the heap when they are done; AutoBlack has been known to crash after such dirty predecessors. Renaming the files so AutoBlack loads first usually clears up the problem.
