Setting Up a Screen Saver Application

Background

AutoLaunch runs an application of your choosing when your Macintosh is idle.  You can specify any application as the "screen saver," including programs that may not really do anything to the screen, such as AppleScript applets, Microsoft Excel, networked rendering engines - whatever.  The one restriction is that the application must have its own icon (it cannot have a "generic" application icon) in order for AutoLaunch to find it on your hard disk.

This section explains how to configure AutoLaunch, and provides some technical details on how the screen saver application is located and launched. 

Setup

To turn on AutoLaunch, simply click on the "On" radio button in the control panel and enter the number of minutes of idle time you'd like AutoLaunch to wait before running the screen saver application.  Note that "idle time" is defined as the amount of time since you last moved the mouse, typed on the keyboard, or inserted a disk. 

In order for anything to really happen when your Mac is idle, you must click the "Choose" button and select an application for AutoLaunch to run.  

When the application is running and mouse or keyboard activity "wakes up" your Macintosh, AutoLaunch can do one of three things, as dictated by the checkboxes below the "Choose" button:

1.  Kill the application.  This forcibly quits without letting the application ask you if you want to save unsaved changes, remember new settings, etc.

WARNING:  Some applications may not like being killed (would you?).  Because of the way they work, programs that use MacTCP are particularly susceptible - killing them will generally crash your Mac.

2.  Quit the application.  This does the equivalent of choosing "Quit" from the file menu.  The application will ask you to save your changes or whatever else may be appropriate.  Some ill-behaved applications may not respond to this method, so you may have to resort to option #1.

3.  Leave the application running.   When neither checkbox is checked, AutoLaunch just lets the appliction keep running.

AutoLaunch also watches for the mouse in two corners of the screen, giving you a way to run your application immediately or prevent it from running even after the machine has been idle.   You indicate which corner of the screen should be "hot" by clicking the radiobuttons in the miniature screen rectangles on the right side of the control panel.

Details

AutoLaunch uses the Finder's Desktop database to locate the screen saver application on disk.  Since the Desktop database only tracks applications with a BNDL resource (this is the resource that defines the application's icon), you cannot use AutoLaunch to run applications that have a generic icon.

AutoLaunch finds the application in the Desktop database using its creator type.  If more than one application with the same creator type exists (multiple copies or different versions of an application are on the hard disk, or multiple applications have the same creator, as is the case with AppleScript applets), AutoLaunch compares the names of those applications and runs the one with same name as the one specified with the "Choose" button.