event-handler-attribute-replace-preserves-passive.html

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This WPT test may be referenced by the following Test IDs:
- /dom/events/event-handler-attribute-replace-preserves-passive.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<title>Event handler attribute replacement via setAttribute preserves passive flag</title>

<link rel="help" href="https://html.spec.whatwg.org/multipage/webappapis.html#event-handler-content-attributes">

<link rel="help" href="https://dom.spec.whatwg.org/#dom-eventtarget-addeventlistener">

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<body>

<script>

// Wheel event listeners on document/body are made passive by default by user

// agents. When such a listener is replaced via setAttribute (e.g. setting the

// onwheel attribute again), the passive flag should be preserved from the

// existing listener rather than being reset to defaults.

test(function() {

    // Set onwheel on body via setAttribute for the first time.

    // The UA may make this passive since wheel listeners on body are passive

    // by default per spec recommendation.

    document.body.setAttribute("onwheel",

        "event.preventDefault(); window._defaultPrevented1 = event.defaultPrevented;");

    var event1 = new Event("wheel", { cancelable: true });

    document.body.dispatchEvent(event1);

    var initialPassive = !window._defaultPrevented1;

    // Now replace the onwheel handler via setAttribute again.

    document.body.setAttribute("onwheel",

        "event.preventDefault(); window._defaultPrevented2 = event.defaultPrevented;");

    var event2 = new Event("wheel", { cancelable: true });

    document.body.dispatchEvent(event2);

    // The passive flag from the initial listener should be preserved after

    // replacement via setAttribute.

    assert_equals(window._defaultPrevented2, window._defaultPrevented1,

        "preventDefault behavior should be the same before and after setAttribute replacement");

    // Clean up.

    document.body.removeAttribute("onwheel");

    delete window._defaultPrevented1;

    delete window._defaultPrevented2;

}, "Replacing a wheel event handler attribute on body via setAttribute preserves its passive flag");

test(function() {

    document.documentElement.setAttribute("onwheel",

        "event.preventDefault(); window._defaultPrevented3 = event.defaultPrevented;");

    var event1 = new Event("wheel", { cancelable: true });

    document.documentElement.dispatchEvent(event1);

    document.documentElement.setAttribute("onwheel",

        "event.preventDefault(); window._defaultPrevented4 = event.defaultPrevented;");

    var event2 = new Event("wheel", { cancelable: true });

    document.documentElement.dispatchEvent(event2);

    assert_equals(window._defaultPrevented4, window._defaultPrevented3,

        "preventDefault behavior should be the same before and after setAttribute replacement");

    document.documentElement.removeAttribute("onwheel");

    delete window._defaultPrevented3;

    delete window._defaultPrevented4;

}, "Replacing a wheel event handler attribute on document element via setAttribute preserves its passive flag");

</script>

</body>