当滚动条出现时，eventlistener / CSS伪类

Question

is there a javascript eventlister or css pseudo class when a scrollbar appears and disappears? For example system Mac OS, the Scrollbars are default hidden, when you start scrolling they do appear. Same for Windows Internet Explorer >= 10. I want to know that the scrollbars are appeared and disappeared. My first test:

var doscroll = false,
        $html = $('html'),
        timer;
$(window).on('scroll', function () {
    if (!doscroll) {
        doscroll = true;
        $html.addClass('doscroll');
    }
    clearTimeout(timer);
    timer = setTimeout(function () {
        doscroll = false;
        $html.removeClass('doscroll');
    }, 2000);
})

But when I click on the Scrollbar and do not scroll the timer removes the docsroll-class, and I also don't know the exact time when to remove the doscroll-class.

Has any one a better solution / idea?

Thanks Oliver

Answer 1

No. Scrollbars are implementation dependent.

The spec says

The scrolling mechanism depends on the UA. The most common mechanism is a scrollbar, but panners, hand cursors, page flickers, etc. are also possible.

Therefore, some implementations have no scrollbars, and some others have but never hide them. Thus that event would make no sense.