Re-architect application

[mdippery]

Due to the way login items work in OS X from 10.6 on, Blackout basically needs to have a helper app that actually captures the keystroke and activates the screensaver. This is a somewhat large departure from what I've been doing. Essentially, the app will consist of two components:

1. Blackout.app, which is just a simple app for setting preferences.
2. BlackoutHelper.app, which will actually run in the background and listen for keystrokes to control the screensaver.

Blackout.app can communicate with BlackoutHelper.app via some sort form of IPC (are distributed objects/notifications still used, or is there a better mechanism these days), such as when the hotkey needs to be updated.

This screencast has more details. However, in comparison to the screencast, mine will essentially be flipped, with the "main" application just being a thin GUI for setting preferences, and the helper being the daemon that will actually be launched.

[mdippery]

On the other hand, this architecture is sort of a pain, because how will the application run such that the user can launch and quit it manually, without having to make it a login item? The aforementioned screencast may be on the right track as far as the architecture goes. I may just have to hack something together that will make the helper app check to see if Blackout is already running and only launch it if it is not.

Of course, this brings up the question: How to implement #4? Can the user just option-click Blackout to bring up the prefpane, without essentially launching a second version of the application? My my, this is getting to be difficult, and I definitely need to think about the architecture a bit more.

[mdippery]

The answer to the above question is yes: As of right now, double-clicking Blackout will open multiple copies of it. So I really do need to re-think the architecture.

[mdippery]

Here's how I will deal with launching the helper app:

1. When the "main" (GUI) app launches, it will check to see if the helper is running.
2. Using this information, it will set an NSSegmentedControl to ON or OFF.
3. Toggling the NSSegmentedControl will enable or disable the daemon. Therefore, it will only be possible to both run Blackout and launch it at startup. You can't "just run it" without it being a login item. (Maybe that will be a v1.1 feature.)

This should avoid any issues with the helper app being launched several times. Just in case, I will add code to the helper app to check to see if a copy is already running at startup, and terminate itself it is is.

[mdippery]

This notification may help with this issue. I am thinking that there is no helper app, just the main app, which can present a preferences dialog whenever it is launched or double-clicked.