the secure, sleepy screen saver

Scrounging a lot of forums, I came up with a solution for an OS X screen saver that serves a lot of my needs. If you follow these instructions, you will ...

• have a screen saver that sleeps the display instead of drawing pretty pictures on it.
• be prompted for your password when you disturb the screen saver.
• be able to immediately start your screen saver via your keyboard if you want to safely walk away from your computer.
• be able to temporarily disable your screen saver while watching a movie etc.
  

The sleepy screen saver

I've always wanted my screen saver to just put the display to sleep, but that's not been an OS X option out of the box.

This hint comment offers some C code for sleeping the display immediately, which it seems is the only way to do it from the command line! There's the CTRL-SHIFT-Eject keystroke, but AppleScript cannot emulate the Eject keystroke. You can compile that code (change the function name to main) with

gcc -framework CoreFoundation -framework IOKit

if you've installed the XCode tools.

Now you have an executable that just sleeps the display.

Why use a screen saver at all?

A fine question. I could just set my display to sleep before my screen saver starts. There's a reason.

Phil has got me thinking about security recently, so I want my laptop to prompt for a password when someone wakes the display from sleep/disturbs the screen saver. This is easy to setup for the screen saver, but not so much for waking display. The best alternative I can find is SleepWatcher, but that project seems a little too fragile for me to depend on it. It would let me execute a script when the display wakes, but I also don't want to write a script that emulates the password prompt.

So I'm using a screen saver because I want the password prompt aspect.

How to make the application a screen saver

There are tutorials for making screen savers, and XCode even has a project for them (under Standard Apple Plug-ins), but I don't know Objective-C and there's more function stubs to fill out than I'd like. So I'm going to cheat and use ScriptSaver instead. It only runs AppleScripts, so we use a simple little script to invoke our executable according to this note. I put my executable in /usr/local/bin and made a /usr/local/AppleScripts directory for my script. Check your PATHs and such.

Final touches

• I made sure, in the Security preference pane, that a password is required to wake this computer from sleep or screen saver.
• I use Quicksilver, because I prefer the keyboard to the mouse. OS X lets you use a Hot Corner for invoking the screen saver, but that's hard to activate with the keyboard... so I added /System/Library/Frameworks/ScreenSaver.framework/Versions/A/Resources/ScreenSaverEngine.app to Quicksilver's catalog. That way I can invoke the screen saver just like any other program. (Phil pointed me to this hint; if you don't want to install Quicksilver.)
  
• Temporarily disabling the screen saver for movies and such is comparable to disabling sleep, but it's a bit more complicated (see HippoMan's post at 12-31-2008, 08:26 PM for the solution – also, applaud him for politely putting up with a lot of stupid responses in that thread).