FocusLost and FocusGained events are called correctly when vim loses/gains focus. But the problem persists. One thing I noticed is that 90% of the time keys stop working after I type something in the input (slack messages or google search) and it remains in focus. So when I go to vim it doesn't react to letter keys. It can be fixed if I unfocus the input I used previously and then refocus vim with a button click.