Re: popup window filter, what is <80><fd>` ?

It looks like it happens on cursorhold event, not 100% sure though.

Indeed, if I change `set updatetime=1000` then I get this every second:

vim9script

def Test()
    var prompt: string = ''
    const wid: number = popup_create('', {
        minwidth: 20,
        maxheight: 1,
        mapping: false,
        filter: (winid: number, key: string): bool => {
            if key == "\<esc>"
                popup_close(winid, -1)
            else
                prompt ..= key
                popup_settext(winid, prompt)
            else
                return false
            endif
            return true
        },
        callback: (_: number, result: number) => {
            if result == 0
                echomsg prompt
            endif
        }
    })
enddef

Test()