Comment 4 for bug 636311

OK, just to confuse matters:

For the above description, I was using the mouse left-handed. I described right and left buttons according to function on the computer, i.e. what I called the right button, which invokes a context menu, is physically the one on the left. This raises the same event (button 3) as occurs when I press a special key. I'd forgotten that left-handed is the exception until just now.

When testing the same thing with the mouse right-handed, a special key fires a button 1 press event. In other words, whichever hand the mouse is set for, it signals a 'press' corresponding to the physical-left button. As before, there's no corresponding ButtonRelease, so it's as if that button is 'held down'.

I hope this helps someone to understand what might be causing this behaviour.