CODEWITHSUNDEEP
objective-cmacoscocoa
Irae Carvalho
Irae Carvalho

Reputation: 787

How can I detect/observe when third party app launches a full screen process?

I would like to build a helper app for gamers, and to build some extra functionality I would like to observe/time certain third party games behaviors, more specifically when the game actually launches the full screen process.

For example: my app is a system tray app, the game has a "launcher" app with lobby and menu screens. Once the game launches the extra process, usually OS X will switch resolutions (optionally) and my App would be notified somehow. Then I can start a timer. Once game match finishes, either the process is closed, or the game is not full screen anymore, my app gets a second notification and I can stop the timer.

Are there official Apple APIs that provide any way to observe/poll for the app going full screen and/or launch additional windows that I can reliably assume it's the actual game screen?

Upvotes: 3

Views: 551

Answers (2)

Ken Thomases
Ken Thomases

Reputation: 90521

I doubt you're going to find a completely comprehensive solution. There are many ways for apps to achieve a full-screen experience and most don't provide a notification about that fact.

A full-screen app can modify the presentationOptions of NSApplication to hide the Dock and menu bar. Another app can use key-value observing to monitor its application object's currentSystemPresentationOptions property, which will reflect the current system status.

A full-screen app can capture the displays (although Apple discourages this technique). You can try to detect this by calling CGDisplayIsCaptured(), although it's been deprecated since 10.9 with no replacement. It may be possible that, if you register a callback with CGDisplayRegisterReconfigurationCallback(), you'll get called when something captures the display. However, capturing the display is sort of about preventing other processes from noticing such changes, so maybe not. In that case, you'd have to poll. You might also poll for the current display mode; changing the mode is the primary reason why a game would capture the display in the first place.

A full-screen game could also just create a borderless window the size of the screen and set its window level to be in front of the Dock and menu bar (and other apps' windows). There's not really a notification about this. You could detect it using the CGWindowList API, but you would have to poll. For example, you could call CGWindowListCopyWindowInfo(kCGWindowListOptionOnScreenOnly, kCGNullWindowID) and iterate through the dictionaries looking for one the size of the screen and at a window level above kCGStatusWindowLevel.

(You might be able to use the Accessibility API to get a notification when the frontmost window changes, so you'd only have to poll when that happens.)

Upvotes: 3

d00dle
d00dle

Reputation: 1316

You cannot observe a notification if there is none. So firstly you need to know if the app you want to observe is actually sending a notification that is observable. You cannot 'hook' into other apps without their planned consent.

Upvotes: 0

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