No keyboard shortcut uses only printable characters

Rule Type:atomic
Rule Id: ffbc54
Last modified: Jan 11, 2022
Accessibility Requirements Mapping:
- 2.1.4 Character Key Shortcuts (Level A)
  - Learn More about 2.1.4 Character Key Shortcuts
  - Required for conformance to WCAG 2.1 on level A and higher.
  - Outcome mapping:
    Any failed outcomes: success criterion is not satisfied.
    All passed outcomes: success criterion is satisfied.
    An inapplicable outcome: success criterion needs further testing.
Input Aspects:
- DOM Tree

Description

This rule checks that if keyboard shortcuts are implemented using only printable characters, then there is a mechanism to disable the shortcut, or to remap the shortcut to use one or more non-printable character keys, or the shortcut for a user interface component is only available when that component has focus.

Applicability

This rule applies to any keyboard event for which all of the following is true:

the event's attribute key is a printable character key; and
the event's method getModifierState returns false for each of the valid modifier keys; and
the event causes changes in the content of the HTML document.

Expectation

For each test target at least one of the following is true:

disable/remap: there is at least one set of clearly labeled instruments to block events that use the same key as the test target and whose getModifierState method returns false for each of the valid modifier keys; or
focus: the event target is an inheriting semantic widget.

Assumptions

If there are ways to disable the result of keyboard events that do not require the user to interact with the web page (e.g. a setting at the operating system level), failing this rule might not be a failure of the success criterion.
After being disabled, the event remains disabled until being re-enabled again. If the event is re-enabled through other non-user controlled means (e.g. a timeout) then this rule may pass while Success Criterion 2.1.4: Character Key Shortcuts is not satisfied.

Accessibility Support

Currently keyboard events only support the types keydown and keyup. Keyboard events of type keypressed are considered legacy keyboard events and are thus ignored by this rule.

Background

The instruments used to pass this rule (if any), must meet all level A Success Criteria in order to fully satisfy Success Criterion 2.1.4: Character Key Shortcuts. These extra requirements are left out of this rule, and should be tested separately. This rule allows changes to the content when a user interface component has focus to meet the "Active only on focus" requirement from Success Criterion 2.1.4. As explained in the Event dispatch and DOM event flow section of the UI Events Working Draft, each keyboard event is dispatched to an event target. The event target is the element that has focus. As such, the "Active only on focus" requirement from Success Criterion 2.1.4 is implied by saying that the event target is an inheriting semantic widget.

The "Turn off" and "Remap" requirements from Success Criterion 2.1.4 are combined in the disable/remap item of the Expectation section. For the disable requirement, changes in content that are made through keyboard events with a printable character value for the key attribute and a getModifierState return value of false for each of the valid modifier keys effectively need to be blocked (in other words, turned off or disabled). The remap requirement unblocks the events if the getModifierState query returns true for at least one of the valid modifier keys. Once the getModifierState returns true for at least one of the valid modifier keys of a keyboard event, such keyboard event is no longer applicable for the rule and it passes the "Remap" requirement from Success Criterion 2.1.4.

Bibliography

Test Cases

Passed

Passed Example 1

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This HTML document is listening to keyboard events for which the attribute key is a printable character and the method getModifierState returns false, and which cause changes in content. There exists an instrument to disable the keyboard event so that same key events are blocked unless getModifierState("Control") returns true, therefore meeting the disable/remap expectation.

<html>
	<head>
		<title>Passed Example 1</title>
		<script src="/test-assets/ffbc54/shortcut.js"></script>
	</head>
	<body onload="registerShortcut({id: 'singleShortcut', shortcutKey: '+'}); activateShortcuts();">
		<label for="target">Add to list (press "+" to add):</label>
		<input type="text" id="target" />
		<div>
			<div>Remap shortcut</div>
			<div>
				<label>
					<input id="remap" type="checkbox" onclick="toggleModifier('singleShortcut', this.checked)" />
					Use "ctrl" key together with the "+" key
				</label>
			</div>
		</div>
		<br />
		<div>
			To do list
		</div>
		<ul id="list"></ul>
	</body>
</html>

Passed Example 2

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This HTML document is listening to keyboard events for which the attribute key is a printable character and the method getModifierState returns false, and which cause changes in content. There exists an instrument to disable the keyboard event. A disabled event implies that the event is disabled when the getModifierState method returns false.

<html>
	<head>
		<title>Passed Example 2</title>
		<script src="/test-assets/ffbc54/shortcut.js"></script>
	</head>
	<body onload="registerShortcut({id: 'singleShortcut', shortcutKey: '+'}); activateShortcuts();">
		<label for="target">Add to list (press "+" to add):</label>
		<input type="text" id="target" />
		<label>
			<input type="checkbox" onclick="toggleDisabled('singleShortcut', !this.checked)" checked />
			Toggle single character keyboard shortcut
		</label>
		<br />
		<div>
			To do list
		</div>
		<ul id="list"></ul>
	</body>
</html>

Passed Example 3

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This HTML document is listening to keyboard events for which the attribute key is a printable character and the method getModifierState returns false, and which cause changes in content. For each keyboard event causing changes in content, there exists an instrument to disable it so that same key events are blocked unless getModifierState("Control") returns true, therefore meeting the disable/remap expectation.

<html>
	<head>
		<title>Passed Example 3</title>
		<script src="/test-assets/ffbc54/shortcut.js"></script>
	</head>
	<body
		onload="registerShortcut({id: 'firstShortcut', shortcutKey: '+'}); registerShortcut({id: 'secondShortcut', shortcutKey: 'a'}); activateShortcuts();"
	>
		<label for="target">Add to list (press "+" or "a" to add):</label>
		<input type="text" id="target" />
		<div>
			<div>Remap shortcut</div>
			<div>
				<label>
					<input id="remap1" type="checkbox" onclick="toggleModifier('firstShortcut', this.checked)" />
					Use "ctrl" key together with the "+" key
				</label>
				<label>
					<input id="remap2" type="checkbox" onclick="toggleModifier('secondShortcut', this.checked)" />
					Use "ctrl" key together with the "a" key
				</label>
			</div>
		</div>
		<br />
		<div>
			To do list
		</div>
		<ul id="list"></ul>
	</body>
</html>

Passed Example 4

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This HTML document is listening to keyboard events for which the attribute key is a printable character and the method getModifierState returns false, and which cause changes in content. There exists an instrument to disable those keyboard events that cause changes in content so that same key events are blocked unless getModifierState("Control") returns true. In this example, the same instrument is used to remap all keyboard events.

<html>
	<head>
		<title>Passed Example 4</title>
		<script src="/test-assets/ffbc54/shortcut.js"></script>
	</head>
	<body
		onload="registerShortcut({id: 'firstShortcut', shortcutKey: '+'}); registerShortcut({id: 'secondShortcut', shortcutKey: 'a'}); activateShortcuts();"
	>
		<label for="target">Add to list (press "+" or "a" to add):</label>
		<input type="text" id="target" />
		<div>
			<div>Remap shortcut</div>
			<div>
				<label>
					<input
						id="remap"
						type="checkbox"
						onclick="toggleModifier('firstShortcut', this.checked); toggleModifier('secondShortcut', this.checked);"
					/>
					Use "ctrl" key together with the "+" or "a" key
				</label>
			</div>
		</div>
		<br />
		<div>
			To do list
		</div>
		<ul id="list"></ul>
	</body>
</html>

Passed Example 5

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<html>
	<head>
		<title>Passed Example 5</title>
		<script src="/test-assets/ffbc54/shortcut.js"></script>
	</head>

	<body onload="registerShortcut({shortcutKey: '+', focusOnly: true}); activateShortcuts();">
		<label for="target">Add to list (press "+" to add):</label>
		<input type="text" id="target" />
		<br />
		<div>
			To do list
		</div>
		<ul id="list"></ul>
	</body>
</html>

Passed Example 6

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This HTML document is listening to keyboard events for which the attribute key is a printable character and the method getModifierState returns false, and which cause changes in content. There exists a set of clearly labeled instruments to disable or to remap the keyboard event so that same key events are blocked unless getModifierState("Control") returns true.

<html>
	<head>
		<title>Passed Example 6</title>
		<link rel="stylesheet" type="text/css" href="/test-assets/ffbc54/styles.css" />
		<script src="/test-assets/ffbc54/shortcut.js"></script>
	</head>
	<body onload="registerShortcut({id: 'singleShortcut', shortcutKey: '+'}); activateShortcuts();">
		<div id="overlay">
			<p>Disable/remap shortcut</p>
			<label>
				<input type="checkbox" onclick="toggleDisabled('singleShortcut', !this.checked)" checked />
				Toggle single character keyboard shortcut
			</label>
			<br />
			<label>
				<input id="remap" type="checkbox" onclick="toggleModifier('singleShortcut', this.checked)" />
				Use "ctrl" key together with the "+" key
			</label>
			<br />
			<button onclick="closeModal();">Dismiss</button>
		</div>
		<p>To control the shortcuts activate the "Control shortcuts" button.</p>
		<input type="button" onclick="openModal()" value="Control shortcuts" />

		<label for="target">Add to list (press "+" to add):</label>
		<input type="text" id="target" />
		<div>
			To do list
		</div>
		<ul id="list"></ul>
	</body>
</html>

Failed

Failed Example 1

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This HTML document is listening to keyboard events for which the attribute key is a printable character and the method getModifierState returns false, and which cause changes in content. There is no instrument to disable or remap the keyboard event and the keyboard events are not blocked when no widget has focus.

<html>
	<head>
		<title>Failed Example 1</title>
		<script src="/test-assets/ffbc54/shortcut.js"></script>
	</head>
	<body onload="registerShortcut({shortcutKey: '+', disabled: false}); activateShortcuts();">
		<label for="target">Add to list (press "+" to add):</label>
		<input type="text" id="target" />
		<br />
		<div>
			To do list
		</div>
		<ul id="list"></ul>
	</body>
</html>

Failed Example 2

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This HTML document is listening to keyboard events for which the attribute key is a printable character and the method getModifierState returns false, and which cause changes in content. There is an instrument to disable or remap the keyboard event so that same key events are blocked unless getModifierState("Control") returns true, but the instrument is not in a clearly labeled location.

<html>
	<head>
		<title>Failed Example 2</title>
		<link rel="stylesheet" type="text/css" href="/test-assets/ffbc54/styles.css" />
		<script src="/test-assets/ffbc54/shortcut.js"></script>
	</head>
	<body onload="registerShortcut({id: 'singleShortcut', shortcutKey: '+'}); activateShortcuts();">
		<div id="overlay">
			<p>Disable/remap shortcut</p>
			<label>
				<input type="checkbox" onclick="toggleDisabled('singleShortcut', !this.checked)" checked />
				Toggle single character keyboard shortcut
			</label>
			<br />
			<label>
				<input id="remap" type="checkbox" onclick="toggleModifier('singleShortcut', this.checked)" />
				Use "ctrl" key together with the "+" key
			</label>
			<br />
			<button onclick="closeModal();">Dismiss</button>
		</div>

		<input type="button" onclick="openModal()" value="Open modal" />

		<label for="target">Add to list (press "+" to add):</label>
		<input type="text" id="target" />
		<div>
			To do list
		</div>
		<ul id="list"></ul>
	</body>
</html>

Inapplicable

Inapplicable Example 1

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This HTML document has a keyboard event dispatched to an event target but it only causes changes in content if the event's attribute key is not a printable character (in this example, the Escape key).

<html>
	<head>
		<title>Inapplicable Example 1</title>
		<script src="/test-assets/ffbc54/shortcut.js"></script>
	</head>

	<body onload="registerShortcut({shortcutKey: 'Escape'}); activateShortcuts();">
		<label for="target">Add to list (press "esc" to add):</label>
		<input type="text" id="target" />
		<br />
		<div>
			To do list
		</div>
		<ul id="list"></ul>
	</body>
</html>

Inapplicable Example 2

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This HTML document has a keyboard event dispatched to an event target with the attribute key being a printable character but it does not cause changes in content unless the getModifierState returns true.

<html>
	<head>
		<title>Inapplicable Example 2</title>
		<script src="/test-assets/ffbc54/shortcut.js"></script>
	</head>

	<body onload="registerShortcut({shortcutKey: '+', ctrlKey: true}); activateShortcuts();">
		<label for="target">Add to list (press "ctrl" and "+" to add):</label>
		<input type="text" id="target" />
		<br />
		<div>
			To do list
		</div>
		<ul id="list"></ul>
	</body>
</html>

Glossary

Blocked event

A blocked event makes no changes to the content of the web page.

Changes in content

A event originated change in the content of a web page occurs when, by comparing the web page before and 1 minute after the event firing, at least one of the following occurs:

visible changes: the rendered pixels change in any part of the document that is currently within the viewport or that can be brought into the viewport via scrolling; or
accessibility tree changes: any state, property or event of a node representing an accessible object of the accessibility tree changes, or any node is inserted in, or removed from the accessibility tree; or
audible changes: the audio rendered by the web page changes.
If the web page is rendering time-based media, rendered pixels and audio will be changing as part of the playback. The comparison in this instance should compare the pixels and audio that are rendered if the event is not fired, with the ones that are rendered if the event is fired.

Assumptions:

This definition assumes that there are no changes in the content of the web page caused by another event. If this is not the case, changes may be attributed to the wrong event.
This definition assumes that the changes happen within a 1 minute time span after the event firing and therefore the comparison between the page before and after the event firing can be made at any time after that time span elapses. If there are changes after this time span, this definition may not detect them. The arbitrary 1 minute time span, selected so that testing this rule would not be impractical, is not included in WCAG.

Clearly labeled location

Secondary information and alternative controls of functionality are often not displayed together with primary information or functionality. For example, an option to change a web page to dark mode may be placed on an options page instead of being available on every page and page state of a website. Another example is a maps application, where, instead of using GPS, an option is available in a dropdown menu to set the current location of the device. Such content should be placed in a clearly labeled location.

The location of a target is said to be clearly labeled when the target can be found by activating "identifiable" instruments which either lead the user to find the target, or to another page or page state from which this action can be repeated until the target is found.

Whether or not the content is "clearly labeled" depends on the starting point of the search. If page A has a link which clearly "identifies" some piece of content, then the location of the content is clearly labeled. Page B, which can be in the same website, may not have such a link or may have a link with a link text that does not "identify" target content or which can be interpreted to "identify" more than one target, and so the location of the content starting from page B is not clearly labeled.

For the purpose of this definition, an instrument is identifiable if any text or other content with a text alternative, allows any user to identify an element with a semantic role that inherits from widget.

A web page changes state when the document's body changes without a change in the document's URL.

Inheriting Semantic Role

An element with an inheriting semantic role of X is any element with a non-abstract semantic role that inherits from X, or is the same as X.

Example: An "inheriting semantic link" is any element that either has the semantic role of link or a semantic role that inherits from the link role, such as doc-biblioref.

Instrument to achieve an objective

An HTML element that when activated allows an end-user to achieve an objective.

Note: Any rule that uses this definition must provide an unambiguous description of the objective the instrument is used to achieve.

Background About Instrument for Instrument to achieve an objective

This definition is a more restrictive version of WCAG's definition of mechanism, notably restricting it to the current document. WCAG has a note that "The mechanism needs to meet all success criteria for the conformance level claimed." This includes all the level A criteria such as Success Criterion 2.1.1 Keyboard (the mechanism must be keyboard accessible) or Success Criterion 4.1.2 Name, Role, Value (the mechanism must be exposed to assistive technologies and have an accessible name). This definition, and the rules using it, leaves these extra requirements out. This avoids reporting the same component twice for the same reason (e.g., missing an accessible name) under two different rules and Success Criteria, and helps pinpoint the error related to each Success Criterion. Instruments should nonetheless be fully accessible at the correct conformance level (depending on the rule using them).

Outcome

An outcome is a conclusion that comes from evaluating an ACT Rule on a test subject or one of its constituent test target. An outcome can be one of the three following types:

Inapplicable: No part of the test subject matches the applicability
Passed: A test target meets all expectations
Failed: A test target does not meet all expectations

Note: A rule has one passed or failed outcome for every test target. When there are no test targets the rule has one inapplicable outcome. This means that each test subject will have one or more outcomes.

Note: Implementations using the EARL10-Schema can express the outcome with the outcome property. In addition to passed, failed and inapplicable, EARL 1.0 also defined an incomplete outcome. While this cannot be the outcome of an ACT Rule when applied in its entirety, it often happens that rules are only partially evaluated. For example, when applicability was automated, but the expectations have to be evaluated manually. Such "interim" results can be expressed with the incomplete outcome.

Printable characters

A printable character is a character that occupies a printing position on a display.

These characters correspond to the following Unicode categories:

Letter: 'LC', 'Ll', 'Lm', 'Lo', 'Lt', 'Lu'
Number: 'Nd', 'Nl', 'No'
Mark: 'Mc', 'Me', 'Mn'
Punctuation: 'Pc', 'Pd', 'Pe', 'Pf', 'Pi', 'Po', 'Ps'
Symbol: 'Sc', 'Sk', 'Sm', 'So'
Space: 'Zs'

Same key events

Two keyboard events are same key events if they have the same value for all the following attributes:

key
code
location
repeat
isComposing

Semantic Role

The semantic role of an element is determined by the first of these cases that applies:

Conflict If the element is marked as decorative, but the element is included in the accessibility tree; or would be included in the accessibility tree when it is not programmatically hidden, then its semantic role is its implicit role.
Explicit If the element has an explicit role, then its semantic role is its explicit role.
Implicit The semantic role of the element is its implicit role.

This definition can be used in expressions such as "semantic button" meaning any element with a semantic role of button.

Accessibility Support for Definition of Semantic Role for Semantic Role

There exist popular web browsers and assistive technologies which do not correctly implement Presentational Roles Conflict Resolution. These technologies will not include in the accessibility tree elements that should be, according to Specifications. Thus, some elements that should have their semantic role fixed by case Conflict above are instead falling into case Explicit and are hidden for users of assistive technologies.
A similar conflict exists for focusable elements with a aria-hidden="true" attribute. The WAI ARIA specification does not explain how to solve it. Some browsers give precedence to the element being focusable (and expose it in the accessibility tree) while some give precedence to the aria-hidden attribute (and hide the element).

Set of clearly labeled instruments

A set of clearly labeled instruments is a set of instruments, where each instrument is in the same web page as the test target or can be found in a clearly labeled location from that web page.

Web page (HTML)

An HTML web page is the set of all fully active documents which share the same top-level browsing context.

Note: Nesting of browsing context mostly happens with iframe and object. Thus a web page will most of the time be a "top-level" document and all its iframe and object (recursively).

Note: Web pages as defined by WCAG are not restricted to the HTML technology but can also include, e.g., PDF or DOCX documents.

Note: Although web pages as defined here are sets of documents (and do not contain other kind of nodes), one can abusively write that any node is "in a web page" if it is a shadow-including descendant of a document that is part of that web page.

Useful Links

Implementations

This section is not part of the official rule. It is populated dynamically and not accounted for in the change history or the last modified date. This section will not be included in the rule when it is published on the W3C website.

No Implementations

Implementation reports are not provided for this rule.

Acknowledgments

Authors

Funding

WAI-Tools

Table of Contents

Glossary
Useful Links
Implementations
Acknowledgments