Checkbox Example (Two State)

Read This First

The code in this example is not intended for production environments. Before using it for any purpose, read this to understand why.

This is an illustrative example of one way of using ARIA that conforms with the ARIA specification.

There may be support gaps in some browser and assistive technology combinations, especially for mobile/touch devices. Testing code based on this example with assistive technologies is essential before considering use in production systems.
The ARIA and Assistive Technologies Project is developing measurements of assistive technology support for APG examples.
Robust accessibility can be further optimized by choosing implementation patterns that maximize use of semantic HTML and heeding the warning that No ARIA is better than Bad ARIA.

About This Example

This example implements the Checkbox Pattern for a two state checkbox using div elements.

Similar examples include:

Checkbox (Mixed-State): Demonstrates a checkbox that uses the mixed value for aria-checked to reflect and control checked states within a group of two-state HTML checkboxes contained in an HTML fieldset.

Example

Sandwich Condiments

Lettuce
Tomato
Mustard
Sprouts

Accessibility Features

To help assistive technology users understand that each checkbox is part of a set of related checkboxes named Sandwich Condiments, the checkboxes are wrapped in a group labeled by the h3 heading element.
To enable assistive technology users to perceive the set of checkboxes as a list of four items, each div element that serves as a checkbox is contained within a li element contained by a ul element.
To make it easier to perceive that clicking either the label or checkbox will activate the checkbox, when a pointer hovers over either the checkbox or label, the background color changes, a border appears, and the cursor changes to a pointer.
Because transparent borders are visible on some systems when operating system high contrast settings are enabled, transparency cannot be used to create a visual difference between the element that is focused and other elements. Instead of using transparency, the focused element has a thicker border and less padding. When an element receives focus, its border changes from 0 to 2 pixels and padding is reduced by 2 pixels. When an element loses focus, its border changes from 2 pixels to 0 and padding is increased by 2 pixels.
To ensure the borders of the inline SVG checkbox graphics in the CSS have sufficient contrast with the background when high contrast settings invert colors, the color of the borders are synchronized with the color of the text content. For example, the color of the checkbox borders is set to match the foreground color of high contrast mode text by specifying the CSS currentcolor value for the stroke property of the rect and polyline elements used to draw the checkbox. To make the background of the checkbox graphics match the high contrast background color, the fill-opacity attribute of the rect element is set to zero. If specific colors were instead used to specify the stroke and fill properties, those colors would remain the same in high contrast mode, which could lead to insufficient contrast between the checkbox and the background or even make the checkbox invisible if the color matched the high contrast mode background.
Note: The SVG element needs to have the CSS forced-color-adjust property set to auto for the currentcolor value to be updated in high contrast mode. Some browsers do not use auto for the default value.

Keyboard Support

Key	Function
`Tab`	Moves keyboard focus to the `checkbox`.
`Space`	Toggles checkbox between checked and unchecked states.

Role, Property, State, and Tabindex Attributes

Role	Attribute	Element	Usage
		`h3`	Provides a grouping label for the group of checkboxes.
`group`		`div`	Identifies the `div` element as a `group` container for the checkboxes.
	`aria-labelledby`	`div`	References the `id` attribute of the `h3` element to define the accessible name for the group of checkboxes.
`checkbox`		`div`	Identifies the `div` element as a `checkbox`. The child text content of this `div` provides the accessible name of the checkbox.
	`tabindex="0"`	`div`	Includes the checkbox in the page tab sequence.
	`aria-checked="false"`	`div`	Indicates the `checkbox` is not checked. CSS attribute selectors (e.g. `[aria-checked="false"]`) are used to synchronize the visual states with the value of the `aria-checked` attribute. To support operating system and browser high contrast settings, the CSS `::before` pseudo element and `content` property are used to generate the visual indicators of the checkbox state.
	`aria-checked="true"`	`div`	Indicates the `checkbox` is checked. CSS attribute selectors (e.g. `[aria-checked="true"]`) are used to synchronize the visual states with the value of the `aria-checked` attribute. To support operating system and browser high contrast settings, the CSS `::before` pseudo element and `content` property are used to generate the visual indicators of the checkbox state.

JavaScript and CSS Source Code

CSS: checkbox.css
Javascript: checkbox.js