I need to detect when user's computer goes to idle mode.
I also need to detect when user's computer comes back from the idle mode.

I have an application running in Sys Tray that should let the server know
that the user is inactive / active.

Any advice/resource please?

If you're processing data via a thread, just set the thread to the lowest
or low priority - Windows will automatically schedule the thread to be run
whenever there are free cycles.

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