Programmatically changing screen lock timeout

Question

In my Cocoa application I would like to access and change the computer's screen lock timeout setting. Changing it in System Preferences does not require the user to enter the admin password.

Unfortunately I couldn't find any information in the documentation, and I'm not sure what topic I should look into (security settings / prefPane programming).
Any help would be appreciated.

Answer 1

NSMutableDictionary* plistDict = [[NSMutableDictionary alloc] initWithContentsOfFile:@"/Users/new/Library/Preferences/com.apple.screensaver.plist"];
[plistDict setObject:@"1" forKey:@"askForPassword"];
[plistDict setObject:@"3600" forKey:@"askForPasswordDelay"];
[plistDict writeToFile:@"/Users/new/Library/Preferences/com.apple.screensaver.plist" atomically:YES];  

or From terminal

defaults write com.apple.screensaver askForPasswordDelay 5

Answer 2

The above answer apparently works for some, but on 10.8 it fails if you are using FileVault. The setting will stick, but it won't actually take effect until you launch System Preferences. Luckily, there's a way to 'touch' the setting after you are done:

- (void)touchSecurityPreferences;
{
    NSAppleScript *kickSecurityPreferencesScript = [[[NSAppleScript alloc] initWithSource: @"tell application \"System Events\" to tell security preferences to set require password to wake to true"] autorelease];
    [kickSecurityPreferencesScript executeAndReturnError:nil];
}

Edit Turns out this only works for going from a non-zero setting to zero setting. I assume this is a security thing. To go the other way, launching System Preferences is the only way.

Edit 2 Here's code for launching System Preferences, should you want to do so:

- (void)launchAndQuitSecurityPreferences;
{
    // necessary for screen saver setting changes to take effect on file-vault-enabled systems when going from a askForPasswordDelay setting of zero to a non-zero setting
    NSAppleScript *kickSecurityPreferencesScript = [[[NSAppleScript alloc] initWithSource:
                                                     @"tell application \"System Preferences\"\n"
                                                     @"     tell anchor \"General\" of pane \"com.apple.preference.security\" to reveal\n"
                                                     @"     activate\n"
                                                     @"end tell\n"
                                                     @"delay 0\n"
                                                     @"tell application \"System Preferences\" to quit"] autorelease];
    [kickSecurityPreferencesScript executeAndReturnError:nil];
}