Detect when mouse leaves program window

[bplus]

I could have swore there was a discussion about this before, either on this forum or previous forums, but my searches have come up empty.

How can I detect when the mouse pointer has left the program window?

I seem to remember someone showing how to use an API call ( @SpriggsySpriggs ?) but I didn't have the foresight to add it to my tool box of goodies.

Any suggestions?

Yeah the OS should know where the mouse is, Spriggsy good call, have to decide by OS what "API" to call assuming Linux has similar function and why wouldn't it, sure @mnrvovrfc  will be here to the rescue at mention of Linux and most it's Distros ;-))

OS should also know where the QB64 screen is so by deduction if mouse isn't on QB64 screen it "has left the building".