Thanks for replying, but I've neglected a key piece of information: I'm not using buttons but rectangles with a mouse area.

I have played with onPressed/onReleased, but to no avail. I am also aware of press and hold but couldn't find a working example or even something I could adapt, it's not urgent, but I'd like to solve it.

@Fuzzillogic - I've updated my original question to reflect your comments, thanks.