[Mac Catalyst] DeviceDisplay.KeepScreenOn not being respected on Mac OS

[DanOrlovsky]

Description

We have a Maui app targeting both Windows and MacCatalyst. There is a state the app can be in that requires us to keep the sceen on for the user so the app can function whether the user is at the computer or not.

To facilitate this, we are setting KeepScreenOn on DeviceDisplay:

await MainThread.InvokeOnMainThreadAsync(() =>
{
    DeviceDisplay.Current.KeepScreenOn = true;
});    

This is working fine in windows. The Mac build seems to be ignoring this setting completely.

Steps to Reproduce

Make sure your computer is set to sleep in a reasonable amount of time.

In a MacCatalyst maui app, set the DeviceDisplay.Current.KeepScreenOn to true.

Observe the screen will go to sleep.

Link to public reproduction project repository

https://github.com/DanOrlovsky/MauiBlazorNet9ScreenOnDemo

Version with bug

9.0.0 GA

Is this a regression from previous behavior?

No, this is something new

Last version that worked well

Unknown/Other

Affected platforms

macOS

Affected platform versions

MacOS 14 (Sonoma) and MacOS 15 (Sequoia) and both .Net 8 and .Net 9

Did you find any workaround?

No response

Relevant log output

[MartyIX]

If you would like to check the issue more in detail, I think these pointers can be helpful:

• maui/src/Essentials/src/DeviceDisplay/DeviceDisplay.shared.cs

  Line 9 in c293f60

  public interface IDeviceDisplay

• maui/src/Essentials/src/DeviceDisplay/DeviceDisplay.macos.cs

  Line 23 in c293f60

  IOKit.PreventUserIdleDisplaySleep("KeepScreenOn", out keepScreenOnId);

• maui/src/Essentials/src/Platform/PlatformUtils.macos.cs

  Line 170 in c293f60

  internal static bool PreventUserIdleDisplaySleep(CFString name, out uint id)

• https://developer.apple.com/documentation/iokit/1557134-iopmassertioncreatewithname

By compiling and running https://github.com/dotnet/maui/tree/main/src/Essentials/samples project, you would see what is not working, I believe.

To verify, what is going on, perhaps pmset -g (man) can be used to check if MAUI actually did something or not.

[drasticactions]

@MartyIX Those are for MacOS (AppKit), not Catalyst. Catalyst functions, unless broken out, are with iOS since they are the same APIs.

maui/src/Essentials/src/DeviceDisplay/DeviceDisplay.ios.cs

Lines 12 to 14 in c293f60

	protected override bool GetKeepScreenOn() => UIApplication.SharedApplication.IdleTimerDisabled;
	protected override void SetKeepScreenOn(bool keepScreenOn) => UIApplication.SharedApplication.IdleTimerDisabled = keepScreenOn;

https://developer.apple.com/documentation/uikit/uiapplication/1623070-idletimerdisabled

Apple says it's compatible with Catalyst, and from what I can tell setting that through Essentials is setting that value. IMO I would try running:

UIApplication.SharedApplication.IdleTimerDisabled = true;

In the app and see what it does, in a MAUI UI app and a normal .NET Mac Catalyst one.

[MartyIX]

I'm a bit confused because https://developer.apple.com/documentation/iokit/1557134-iopmassertioncreatewithname mentions Mac Catalyst 13.1+ but happy to learn new stuff.

[drasticactions]

@MartyIX I didn't say that code wouldn't work, the code you pointed to in Extensions would only run on MacOS. It's gated with the macos extension in the filename and only compiles for macOS AppKit. It's referenced in the namespace too: https://github.com/dotnet/maui/blob/c293f603b1b917a7eb206137d014b4e6e347d651/src/Essentials/src/DeviceDisplay/DeviceDisplay.macos.cs#L3C1-L3C14

The code I pointed to is the one being called by essentials. The solution may be to call what you saw instead.

e. I'll try and rephrase it, since reading it again it can be confusing:

The macos file in essentials is only compiled for MacOS AppKit, so that's not the code the user is hitting.