Prevent browser scroll on HTML5 History popstate

Question

Is it possible to prevent the default behaviour of scrolling the document when a popstate event occurs?

Our site uses jQuery animated scrolling and History.js, and state changes should scroll the user around to different areas of the page whether via pushstate or popstate. The trouble is the browser restores the scroll position of the previous state automatically when a popstate event occurs.

I've tried using a container element set to 100% width and height of the document and scrolling the content inside that container. The problem with that I've found is it doesn't seem to be nearly as smooth as scrolling the document; especially if using lots of css3 like box-shadows and gradients.

I've also tried storing the document's scroll position during a user initiated scroll and restoring it after the browser scrolls the page (on popstate). This works fine in Firefox 12 but in Chrome 19 there is a flicker due to the page being scrolled and restored. I assume this is to do with a delay between the scroll and the scroll event being fired (where the scroll position is restored).

Firefox scrolls the page (and fires the scroll event) before popstate fires and Chrome fires popstate first then scrolls the document.

All the sites I've seen that use the history API either use a solution similar to those above or just ignore the scroll position change when a user goes back/forward (e.g. GitHub).

Is it possible to prevent the document being scrolled at all on popstate events?

Answer 1

The solution is to use position: fixed and specify top equal to scroll position of page.

Here is an example:

$(window).on('popstate', function()
{
   $('.yourWrapAroundAllContent').css({
      position: 'fixed',
      top: -window.scrollY
   });

   requestAnimationFrame(function()
   {
      $('.yourWrapAroundAllContent').css({
         position: 'static',
         top: 0
      });          
   });
});

Yes, you instead receive flickering scrollbar, but it is less evil.

Answer 2

This has been a reported issue with the mozilla developer core for more than a year now. Unfortunately, the ticket did not really progress. I think Chrome is the same: There is no reliable way to tackle the scroll position onpopstate via js, since it's native browser behaviour.

There is hope for the future though, if you look at the HTML5 history spec, which explicitly wishes for the scroll position to be represented on the state object:

History objects represent their browsing context's session history as a flat list of session history entries. Each session history entry consists of a URL and optionally a state object, and may in addition have a title, a Document object, form data, a scroll position, and other information associated with it.

This, and if you read the comments on the mozilla ticket mentioned above, gives some indication that it is possible that in the near future scroll position will not be restored anymore onpopstate, at least for people using pushState.

Unfortunately, until then, the scroll position gets stored when pushState is used, and replaceState does not replace the scroll position. Otherwise, it would be fairly easy, and you could use replaceState to set the current Scroll position everytime the user has scrolled the page (with some cautious onscroll handler).

Also unfortunately, the HTML5 spec does not specify when exactly the popstate event has to be fired, it just says: «is fired in certain cases when navigating to a session history entry», which does not clearly say if it's before or after; if it was always before, a solution with handling the scroll event occuring after the popstate would be possible.

Cancel the scroll event?

Furthermore, it would also be easy, if the scroll event where cancelable, which it isn't. If it was, you could just cancel the first scroll event of a series (user scroll events are like lemmings, they come in dozens, whereas the scroll event fired by the history repositioning is a single one), and you would be fine.

There's no solution for now

As far as I see, the only thing I'd recommend for now is to wait for the HTML5 Spec to be fully implemented and to roll with the browser behaviour in this case, that means: animate the scrolling when the browser lets you do it, and let the browser reposition the page when there's a history event. The only thing you can influence position-wise is that you use pushState when the page is positioned in a good way to go back to. Any other solution is either bound to have bugs, or to be too browser-specific, or both.

Answer 3

Now you can do

history.scrollRestoration = 'manual';

and this should prevent browser scroll. This only works right now in Chrome 46 and above, but it seems that Firefox is planning to support it too

Answer 4

Create a 'span' element somewhere at the top of the page and set focus to this on load. The browser will scroll to the focussed element. I understand that this is a workaround and focus on 'span' doesn't work in all browsers ( uhmmm.. Safari ). Hope this helps.

Answer 5

You're going to have to use some kind of horrible browser sniffing here. For Firefox, I would go with your solution of storing the scroll position and restoring it.

I thought I had a good Webkit solution based on your description, but I just tried in Chrome 21, and it seems that Chrome scrolls first, then fires the popstate event, then fires the scroll event. But for reference, here's what I came up with:

function noScrollOnce(event) {
    event.preventDefault();
    document.removeEventListener('scroll', noScrollOnce);
}
window.onpopstate = function () {
    document.addEventListener('scroll', noScrollOnce);
};​

Black magic such as pretending the page is scrolling by moving an absolute positioned element is ruled out by the screen repainting speed too.

So I'm 99% sure that the answer is that you can't, and you're going to have to use one of the compromises you've mentioned in the question. Both browsers scroll before JavaScript knows anything about it, so JavaScript can only react after the event. The only difference is that Firefox doesn't paint the screen until after the Javascript has fired, which is why there's a workable solution in Firefox but not in WebKit.

Answer 6

The following fix should work in all browsers.

You can set scroll position to 0 on the unload event. You can read about this event here: https://developer.mozilla.org/en-US/docs/Web/Events/unload. Essentially, the unload event fires right before you leave the page.

By setting scrollPosition to 0 on unload means when you leave the page with a set pushState it sets scrollPosition to 0. When you return to this page by refreshing or pressing back it will not autoscroll.

//Listen for unload event. This is triggered when leaving the page.
//Reference: https://developer.mozilla.org/en-US/docs/Web/Events/unload
window.addEventListener('unload', function(e) {
    //set scroll position to the top of the page.
    window.scrollTo(0, 0);
});