Making content on focus or hover hoverable, dismissible, and persistent

Applicability

The Technique is applicable to any technology that supports the display of additional content on pointer hover.

This technique relates to Success Criterion 1.4.13: Content on Hover or Focus (Sufficient).

Description

Additional content that is displayed when a user moves the pointer over a trigger or moves the keyboard focus to the trigger (for example, a pop-up) must remain visible to allow users time to read and interact with the content and must allow the user to move the pointer over the additional content.

Low vision users who magnify their screens often see only a small part of the screen at a time (their viewport). This means that the additional content may not be fully visible in the current viewport and users may need to move their mouse over the additional content to read it. Web authors should therefore ensue that additional content stays visible when the pointer moves away from the trigger to the (mostly adjacent) additional content. additional content should also be dismissible without moving the focus, so that users can read content covered by the additional content.

Examples

<p>This is the <a class="a-and-tooltip" id="parent" href="index.html">trigger
<span id="popup" role="tooltip">And this additional text 
gives additional context on the trigger term</span></a>.
Text and popup are <strong>in one link (a)</strong> element.</p>

[role="tooltip"] {
    display: none;
    padding: 0.5em;
    background:white;
    color: black;
    border:solid black 2px;
    width:10em;
}

.a-and-tooltip {
  position: relative;
}

[role="tooltip"] {
    position: absolute;
    left:0;
    top:1em;
}

// trigger and popup inside the same link

var parent = document.getElementById('parent');

parent.onmouseover = function() {
    document.getElementById('popup').style.display = 'block';
}

parent.onmouseout = function() {
    document.getElementById('popup').style.display = 'none';
}

parent.onfocus = function() {
    document.getElementById('popup').style.display = 'block';
}

parent.onblur = function() {
    document.getElementById('popup').style.display = 'none';
}

// hide when ESC is pressed

document.addEventListener('keydown', (e) => {
  if ((e.keyCode || e.which) === 27)
       document.getElementById('popup').style.display = 'none';
});

Tests