I'm writing an application that uses Apple's kiosk mode. I would like to disable the screen saver, but the "ScreenSaverDefaults" class reports itself as being 32-bit only. I can change the build to be 32-bit only, but I would like to be able to support 64-bit architectures as well.
Are there any other Frameworks that I should use to disable the screen saver?
First, you need to save the current setting, so you can put it back the way it was before you turned it off:
NSTask *readTask = [[NSTask alloc] init];
[readTask setLaunchPath:@"/usr/bin/defaults"];
NSArray *arguments = [NSArray arrayWithObjects:@"-currentHost", @"read", @"com.apple.screensaver", @"idleTime", nil];
[readTask setArguments:arguments];
NSPipe *pipe = [NSPipe pipe];
[readTask setStandardOutput:pipe];
NSFileHandle *file = [pipe fileHandleForReading];
[readTask launch];
[readTask release];
NSData *data = [file readDataToEndOfFile];
NSString *originalValue = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
So now you have the original value for the screensaver's idleTime. Great! Don't lose that. Now, you have to set the new value:
NSTask *writeTask = [[NSTask alloc] init];
[writeTask setLaunchPath:@"/usr/bin/defaults"];
NSArray *arguments = [NSArray arrayWithObjects:@"-currentHost", @"write", @"com.apple.screensaver", @"idleTime", @"0", nil];
[writeTask setArguments:arguments];
[writeTask launch];
[writeTask release];
And viola! You've just disabled the screensaver. To re-enable it, just use the second block of code again, but pass in originalValue as the last array object rather than @"0", like so:
NSArray *arguments = [NSArray arrayWithObjects:@"-currentHost", @"write", @"com.apple.screensaver", @"idleTime", originalValue, nil]
Enjoy!
Billy
P.S.: One last thing, you may be tempted to save the NSTask objects to re-use them, but don't. They can only be run once, so you'll have to create new ones every time you want to do this.
For anyone searching for how to do this (like I have been doing) and don't want to mess around with editing the preference files, Apple has a proper method to stop the screen saver from starting up while your application is running.
Technical Q&A QA1160: Preventing sleep
Hope this helps.
What I ended up doing was directly reading the com.apple.screensaver preference file and modifying the idleTime and askForPassword values so that the are zero. A simple CFPreferencesSynchronize and all was well!