Screensaver Question

[Dave Braine]

If I play a video file in full screen, the Screensaver doesn't come on. If I play a video file in it's own window, the Screensaver comes on at the set time.

Why does it come on with the video playing in a window and when it doesn't in full screen?

 

[tjwilliams25]

It's a power-saving technique that the OS does. You can disable the screensaver in the Energy Settings Preference Pane or use an app like Caffeine to keep your screen on. Of course, do so at your own risk for leaving your screen on for long periods of time can decrease the lifespan.

 

[chown33]

If it's a power-management assertion, then try this in Terminal, when it's playing videos, windowed and full-screen:

pmset -g assertions

You could setup a shell script to run it periodically, logging to a file, then look at what changes.

 

[Dave Braine]

I'm not interested in stopping the Screensaver from activating, I'm just wondering why it doesn't come on when watching a video file in Full Screen, but does when watching it in a window. The same computer activity is happening, so what stops it triggering in Full Screen? Or, why does it trigger when watching in a window?

 

[chown33]

I'm not interested in stopping the Screensaver from activating, I'm just wondering why it doesn't come on when watching a video file in Full Screen, but does when watching it in a window. The same computer activity is happening, so what stops it triggering in Full Screen? Or, why does it trigger when watching in a window?

I think screensaver activation is triggered by Power Management (PM). The command that interfaces to PM is 'pmset', and several things are controlled by assertions.

Brief article from 2012 on "power assertions":
http://mikeabdullah.net/power-assertions.html

So if there's a PM assertion that prevents the PM from issuing triggers (events or whatever), then the presence or absence of the PM assertion will lead to differences in screensaver activity. That's why I suggested listing the PM assertions with 'pmset', while running in both modes, and comparing the lists. If there's no difference, then it's something other than a PM assertion, but finding out what PM is doing is a simple and obvious place to start.

I mention PM because I'm almost certain that the 'caffeinate' command creates a PM assertion, or activates 'noidle'. Indeed, the man page for pmset says to use 'caffeinate' in place of the 'noidle' argument.

 

[Gregg2]

PM = Power Management? Just guessing.

 

[chown33]

PM = Power Management? Just guessing.

Yes. I edited my post.

 

[Dave Braine]

That's why I suggested listing the PM assertions with 'pmset', while running in both modes

And how can that be done when watching in Full Screen mode?

 

[chown33]

And how can that be done when watching in Full Screen mode?

Put it in a shell script that loops. Once a minute would be fine (sleep 60).

Run the script in a Terminal window, then hide Terminal. The script will continue to run.