I’d like to be able to decide if the display on the computer where my app is running is currently active or shutdown. I need this for a media center software so I know if I need to activate the display before starting the playback of movies.
So far I tried to use this code:
CGError err0 = CGDisplayNoErr;
CGError err1 = CGDisplayNoErr;
CGDisplayCount dspCount = 0;
err0 = CGGetActiveDisplayList(0, NULL, &dspCount);
CGDisplayCount onlineCount = 0;
err1 = CGGetOnlineDisplayList(0, NULL, &onlineCount);
// Error handling omitted for clarity ;)
NSLog(@"Found %d active and %d online displays", dspCount, onlineCount);
But this code out puts always the same. When I try it on my mac mini, with the display turned off I get the following output:
Found 1 active and 1 online displays
The display is not in a standby mode as I disconnect the power to it when it is not in use. I also tried this on my mac book, which has an internal and an external display. And there it returns:
Found 2 active and 2 online displays
Here it is the same, I deactivate the display and disconnect the power to it but is still returns as beeing active.
The display on the mac mini is a tv-set connected with a dvi to hdmi cable. The display on the mac book is connected with a dvi to vga connector.
I hope somebody has an idea how to solve this. Thanks in advance.
To close this open question. My final findings were that as soon as an external monitor is connected to the computer the given methods will return that it is there. And this also works when the monitor is powered of and not connected to the power source.
So as far as I can tell there is no way to find out what I would like to know 🙁
As I control the event which activates the monitor from my application (in my case its a TV which I control with a usb to ir box) I can get the state of the monitor in this way, but this only has the downside that when the application is crashing, I will lose the state. But thats the best solution I could find.