1922498 - ilgeniodellapizza.com - Scroll does not work correctly

Status: ASSIGNED

(Web Compatibility :: Site Reports, defect, P2)

Description

[Calin Tanase]

Attachment: scroll FF vs Chrome.mp4

Environment:
Operating system: Windows 11
Firefox version: Firefox 130.0.1 (release)/131/133

Preconditions:

• Clean profile

Steps to reproduce:

1. Navigate to: http://www.ilgeniodellapizza.com/le-nostre-pizze.html
2. Scroll up and down the page.

Expected Behavior:
The page is scrolled without any issues.

Actual Behavior:
Keeps jumping when scrolling down and when scrolling up it scrolls automatically all the way to the bottom of the page.

Notes:

• Reproducible on the latest Firefox Release and Nightly
• Reproducible regardless of the ETP setting
• Works as expected using Chrome

---

Created from webcompat-user-report:504699ee-dd61-48e5-bfe9-272000865664

Comment 1

[Kagami Rosylight [:saschanaz] (they/them)]

The page has this code:

    jQuery(document).ready(function() {
        function t() {
            var ua = navigator.userAgent, tem,
                M = ua.match(/(opera|chrome|safari|firefox|msie|trident(?=\/))\/?\s*(\d+)/i) || [];
            if(/trident/i.test(M[1])){
                tem =  /\brv[ :]+(\d+)/g.exec(ua) || [];
                return 'IE '+(tem[1] || '');
            }
            if(M[1] === 'Chrome'){
                tem = ua.match(/\b(OPR|Edge)\/(\d+)/);
                if(tem != null) return tem.slice(1).join(' ').replace('OPR', 'Opera');
            }
            M = M[2]? [M[1], M[2]]: [navigator.appName, navigator.appVersion, '-?'];
            if((tem = ua.match(/version\/(\d+)/i))!= null) M.splice(1, 1, tem[1]);
            return M;
        }

        currentBrowser = t()[0].toLowerCase();
        versionBrowser = t()[1];

        var webKit = 'safari;chrome';
        var IE = 'netscape;msie';
        var mozilla = 'firefox';

        var browserName = [
            (that.options.useOnMozilla ? mozilla : ''),
            (that.options.useOnWebKit ? webKit : ''),
            (that.options.useOnIE ? IE : '')
        ].join(';');

        var neededBrowser = browserName.indexOf(currentBrowser) !== -1;

        if (neededBrowser) {
            ssc_addEvent("mousedown", ssc_mousedown);
            if (currentBrowser === 'firefox' || currentBrowser === "msie" || currentBrowser === "netscape") {
                ssc_addEvent("wheel", ssc_wheel);
            } else {
                if (currentBrowser === 'chrome' && parseInt(versionBrowser) >= 61) {
                    // Use scrollingElement for smooth scrolling using keyboard
                    currentScrollingElement  = document.scrollingElement;
                    // Here is used native chrome smooth scrolling for wheel.
                } else {
                    ssc_addEvent("mousewheel", ssc_wheel);
                }
            }
            ssc_addEvent("load", ssc_init);
        }
    });

The listener has wrong assumptions, that wheelDelta* has the same sign of delta* (it's the opposite!) and that Firefox always uses DOM_DELTA_LINE for deltaMode.

    function ssc_wheel(e) {
        if (!ssc_initdone) {
            ssc_init();
        }
        var t = e.target;
        var n = ssc_overflowingAncestor(t);
        if (!n || e.defaultPrevented || ssc_isNodeName(ssc_activeElement, "embed") || ssc_isNodeName(t, "embed") && /\.pdf/i.test(t.src)) {
            return true;
        }
        var r = e.wheelDeltaX || e.deltaX || 0;
        var i = e.wheelDeltaY || e.deltaY || 0;
        if (n.nodeName === 'BODY' && (currentBrowser === 'firefox' || currentBrowser === "msie" || currentBrowser === "netscape")) {
            n = document.documentElement;
            r = -r;
            i = -i;
            if (currentBrowser === 'firefox') {
                r *= 40;
                i *= 40;
            }
        }

        if (!r && !i) {
            i = e.wheelDelta || 0;
        }
        if (Math.abs(r) > 1.2) {
            r *= that.options.stepsize / 120;
        }
        if (Math.abs(i) > 1.2) {
            i *= that.options.stepsize / 120;
        }
        ssc_scrollArray(n, -r, -i);
    }

Because wheelDelta* has the wrong sign, every time the scroll happens the page goes the opposite direction, and because of the *= 40 part the scroll becomes way too fast.

We can either:

• Delete wheelDelta* properties and force DOM_DELTA_LINE
• or just pretend it's Chrome.

Comment 2

[Jeff Muizelaar [:jrmuizel]]

This seems to be a version of https://github.com/gblazex/smoothscroll-for-websites

Comment 3

[Kagami Rosylight [:saschanaz] (they/them)]

That one seems to have the proper check since forever though 👀 https://github.com/gblazex/smoothscroll-for-websites/blame/809448fe88022ae0f102f687abe0028cbe8c1112/SmoothScroll.js#L352-L361

Comment 4

[Kagami Rosylight [:saschanaz] (they/them)]

Is webcompat:needs-diagnosis accidental?

Comment 5

[Thomas Wisniewski [:twisniewski][PTO August 18-22]]

Yes, sorry, removed.

Comment 6

[Emilio Cobos Álvarez (:emilio)]

Delete wheelDelta* properties and force DOM_DELTA_LINE

That doesn't seem feasible (also with touchpads there might not be a reasonable DOM_DELTA_LINE value... Guess we can convert and fake it?)

or just pretend it's Chrome

Seems easier for this site at least, specially since we don't think this is widespread given comment 3

Comment 7

[Thomas Wisniewski [:twisniewski][PTO August 18-22]]

It actually works fine on my end just to flip wheelDeltaY and scale it down by 40 (it was easy to write such an intervention).

But if that's not going to work well on other platforms, and I ought to also check for wheelMode and such, I'll update.

Comment 8

[Thomas Wisniewski [:twisniewski][PTO August 18-22]]

Attachment: Bug 1922498 - add a desktop-only JS intervention for www.ilgeniodellapizza.com to fix broken wheel-scrolling; r?denschub

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/7a31c48bec94
https://hg.mozilla.org/integration/autoland/rev/bfd05d0c8c57
add a desktop-only JS intervention for www.ilgeniodellapizza.com to fix broken wheel-scrolling; r=denschub,webcompat-reviewers

Comment 10

[Cristina Horotan [:chorotan]]

https://hg.mozilla.org/mozilla-central/rev/bfd05d0c8c57