javascript - Prevent parent page from scrolling when mouse is over embedded iframe in Firefox

Question

...without limiting the scroll inside the iframe or the need to specifically name/tag all scrollable elements.

Imagine google maps widget embedded in parent page. When you zoom in the widget you don't want the parent page to scroll, obviously.

I thought an answer to my previous question solved the problem:

While scrolling inside an iframe, the body doesn't know anything about what happens there. But when iframe scroller reach the bottom or the top, it pass scrolling to body.

Cancel the event that propagates from the iframe.

But the solution does not work in Firefox because Firefox will not - by design - propagate events captured by iframe to the parent page, yet strangely it will scroll the parent page. See jsfiddle here.

$('body').bind('mousewheel DOMMouseScroll', onWheel);

function onWheel (e){
    if (e.target === iframe)
        e.preventDefault();
    console.log(e);
}

So, how do I prevent page from scrolling when user zooms content in embedded iframe, in Firefox?

Answer 1

Since it is a bug in Firefox, the workaround is to work directly with the scroll event, instead of the mousewheel / DOMMouseScroll ones.

The way I did: When user enters the mouse over the iframe, I set a flag to true, and when he leaves the mouse out there, I set it back to false.

Then, when user tries to scroll, but the mouse arrow is inside the iframe, I prevent the parent window scrolling. But, unfortunately, you can't prevent the window scrolling with the usual e.preventDefault() method, so we still need another workaround here, forcing the window to scroll exactly to the X and Y positions it was already before.

The full code:

(function(w) {
    var s = { insideIframe: false } 

    $(iframe).mouseenter(function() {
        s.insideIframe = true;
        s.scrollX = w.scrollX;
        s.scrollY = w.scrollY;
    }).mouseleave(function() {
        s.insideIframe = false;
    });

    $(document).scroll(function() {
        if (s.insideIframe)
            w.scrollTo(s.scrollX, s.scrollY);
    });
})(window);

I've created an immediately executed function to prevent defining the s variable in the global scope.

Fiddle working: http://jsfiddle.net/qznujqjs/16/

---

Edit

Since your question was not tagged with jQuery (although inside it, you've showed a code using the library), the solution with vanilla JS is as simple as the above one:

(function(w) {
    var s = { insideIframe: false } 

    iframe.addEventListener('mouseenter', function() {
        s.insideIframe = true;
        s.scrollX = w.scrollX;
        s.scrollY = w.scrollY;
    });
    
    iframe.addEventListener('mouseleave', function() {
        s.insideIframe = false;
    });

    document.addEventListener('scroll', function() {
        if (s.insideIframe)
            w.scrollTo(s.scrollX, s.scrollY);
    });
})(window);