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Understanding SC 2.5.7:Dragging Movements (Level AA)

In Brief

Goal
Don’t rely on dragging for user actions.
What to do
For any action that involves dragging, provide a simple pointer alternative.
Why it's important
Some people cannot use a mouse to drag items.

Intent

The intent of this Success Criterion is to ensure functionality that uses a dragging movement has another single pointer mode of operation without the need for the dexterity required to drag elements.

Some people cannot perform dragging movements in a precise manner. Others use a specialized or adapted input device, such as a trackball, head pointer, eye-gaze system, or speech-controlled mouse emulator, which may make dragging cumbersome and error-prone.

When an interface implements functionality that uses dragging movements, users perform four discrete actions:

  1. tap or click to establish a starting point, then
  2. press and hold that contact while...
  3. performing a repositioning of the pointer, before...
  4. releasing the pointer at the end point.

Not all users can accurately press and hold that contact while also repositioning the pointer. An alternative method must be provided so that users with mobility impairments who use a pointer (mouse, pen, or touch contact) can use the functionality.

This requirement is separate from keyboard accessibility because people using a touch screen device may not use a physical keyboard. Keyboard specific interactions such as tabbing or arrow keys may not be possible when encountering a drag and drop control. Note, however, that providing a text input can be an acceptable single-pointer alternative to dragging. For example, an input beside a slider could allow any user to enter a precise value for the slider. In such a situation, the on-screen keyboard that appears for touch users offers a single-pointer means of entering an alphanumeric value.

This criterion does not apply to scrolling enabled by the user-agent. Scrolling a page is not in scope, nor is using a technique such as CSS overflow to make a section of content scrollable.

Relationship to other requirements

Success Criteria 2.1.1 Keyboard and 2.1.3 Keyboard (No Exception) require dragging features to be keyboard accessible. However, achieving keyboard equivalence for a dragging operation does not automatically meet this Success Criterion. It is possible to create an interface that works with dragging and keyboard controls that does not work using only clicks or taps. While many designs can be created for a dragging alternative which address both keyboard accessibility and operability by single pointer operation, the two requirements should be assessed independently.

This Success Criterion applies to dragging movements as opposed to pointer gestures, which are covered in Success Criterion 2.5.1 Pointer Gestures. Pointer gestures include directional path-based as well as multi-point gestures. In contrast, for dragging movements, only the start and end point of the movement matters, not the actual path.

Additional examples are selection rectangles that set the first x/y rectangle coordinate at the pointer position via a pointer down-event, and the second x/y coordinate, after a dragging movement, at the next up-event. A similar example is a connecting line drawn between two different items on the screen, as in an allocation test where users are required to draw a line between questions and corresponding answers. In these cases, the dragging movement requires an alternative way to accomplish the same action that does not rely on the dragging movement. For example, two separate single tap or click actions may define the rectangle coordinates or the start and end points of a connecting line.

Alternatives for dragging movements on the same page

Where functionality can be executed via dragging movements and an equivalent option exists that allows for single-pointer access without dragging, this Success Criterion is passed. It does not have to be the same component, so long as the functionality is equivalent. An example is a color wheel where a color can be changed by dragging an indicator. In addition, text fields for the numerical input of color values allow the definition of a color without requiring dragging movements. (Note that a text input is considered device agnostic; although the purpose is to enter characters, text entry can take place through voice, pointer or keyboard.)

Distinguishing dragging movements from path-based pointer gestures

Dragging movements covered in this Success Criterion are pointer interactions where only the start- and endpoints matter. Once the pointer engages with a target, the direction of the dragging movement does not factor into the interaction until the pointer disengages the target. Since the dragging movement does not have an intermediate point, the dragging movement can go in any direction. Path-based gestures are covered in Success Criterion 2.5.1 Pointer Gestures. For more details, refer to Understanding Success Criterion 2.5.1 Pointer Gestures

Benefits

  • Users who struggle with performing dragging movements can still operate an interface with a pointer interface.

Examples

  • A map allows users to drag the view of the map around, and the map has up/down/left/right buttons to move the view as well.
  • A sortable list of elements may, after tapping or clicking on a list element, provide adjacent controls for moving the element up or down in the list by simply tapping or clicking on those controls.
  • A taskboard that allows users to drag and drop items between columns also provides an additional pop-up menu after tapping or clicking on items for moving the selected element to another column by tapping or clicking on pop-up menu entries.
  • A radial control widget (color wheel) where the value can be set by dragging the marker for the currently selected color to another position, also allows picking another color value by tapping or clicking on another place in the color wheel.
  • A linear slider control widget, where the value can be set by dragging the visual indicator (thumb) showing the current value, allows tapping or clicking on any point of the slider track to change the value and set the thumb to that position.
  • A widget where you can drag a gift to one person in a photo of a group of people also has a menu alternative where users can select the person that should receive the gift from the menu.

Techniques

Each numbered item in this section represents a technique or combination of techniques that the WCAG Working Group deems sufficient for meeting this Success Criterion. However, it is not necessary to use these particular techniques. For information on using other techniques, see Understanding Techniques for WCAG Success Criteria, particularly the "Other Techniques" section.

Sufficient Techniques

  1. G219: Ensuring that an alternative is available for dragging movements that operate on content

Failures

The following are common mistakes that are considered failures of this Success Criterion by the WCAG Working Group.

Key Terms

assistive technology

hardware and/or software that acts as a user agent, or along with a mainstream user agent, to provide functionality to meet the requirements of users with disabilities that go beyond those offered by mainstream user agents

Note

Functionality provided by assistive technology includes alternative presentations (e.g., as synthesized speech or magnified content), alternative input methods (e.g., voice), additional navigation or orientation mechanisms, and content transformations (e.g., to make tables more accessible).

Note

Assistive technologies often communicate data and messages with mainstream user agents by using and monitoring APIs.

Note

The distinction between mainstream user agents and assistive technologies is not absolute. Many mainstream user agents provide some features to assist individuals with disabilities. The basic difference is that mainstream user agents target broad and diverse audiences that usually include people with and without disabilities. Assistive technologies target narrowly defined populations of users with specific disabilities. The assistance provided by an assistive technology is more specific and appropriate to the needs of its target users. The mainstream user agent may provide important functionality to assistive technologies like retrieving Web content from program objects or parsing markup into identifiable bundles.

down-event

platform event that occurs when the trigger stimulus of a pointer is depressed

The down-event may have different names on different platforms, such as "touchstart" or "mousedown".

dragging movement

an operation where the pointer engages with an element on the down-event and the element (or a representation of its position) follows the pointer until an up-event

Note

Examples of draggable elements include list items, text elements, and images.

essential

if removed, would fundamentally change the information or functionality of the content, and information and functionality cannot be achieved in another way that would conform

functionality

processes and outcomes achievable through user action

process

series of user actions where each action is required in order to complete an activity

single pointer

pointer input that operates with one point of contact with the screen, including single taps and clicks, double-taps and clicks, long presses, and path-based gestures

up-event

platform event that occurs when the trigger stimulus of a pointer is released

The up-event may have different names on different platforms, such as "touchend" or "mouseup".

user agent

any software that retrieves and presents Web content for users

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