Input Modalities
- Christina Lutz-Hatfield
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Table of Contents
Overview
Make it easier for users to operate functionality through various inputs beyond keyboard.
All functionality should be accessible via pointer input devices, for example, via a mouse pointer, a finger interacting with a touch screen, an electronic pencil/stylus, or a laser pointer.
People operating pointer input devices may not be able to carry out timed or complex gestures. Examples are drag-and-drop gestures and on touch screens, swiping gestures, split taps, or long presses.
Often, people use devices that offer several input methods, for example, mouse input, touch input, keyboard input, and speech input.
These should be supported concurrently as users may at any time switch preferred input methods due to situational circumstances, for example, the availability of a flat support for mouse operation, or situational impediments through motion or changes of ambient light.
A common requirement for pointer interaction is the ability of users to position the pointer over the target. With touch input, the pointer (the finger) is larger and less precise than a mouse cursor. For people with motor impairments, a larger target makes it easier to successfully position the pointer and activate the target.
Pointer Gestures
Not everyone can perform complex and multi-touch gestures.
Let users operate touch screens with one finger and reduced gestures.
Provide single-point operation for all functions.
Please see more detailed information on how to comply with this guideline.
Pointer Cancellation
Make it easier for users to prevent accidental or erroneous pointer input.
People with various disabilities can inadvertently initiate touch or mouse events with unwanted results.
Make pointer cancellation predictable and consistent.
Reduce accidental activation of controls by mouse or touch.
Make it easier for anyone to recover from something they didn’t mean to do.
General Requirements:
For functionality that can be operated using a single pointer, at least one of the following should apply:
1. No Down-Event
The down-event of the pointer is not used to execute any part of the function;
2. Abort or Undo
Completion of the function is on the up-event, and a mechanism is available to abort the function before completion or to undo the function after completion;
3. Up Reversal
The up-event reverses any outcome of the preceding down-event;
4. Essential
Completing the function on the down-event is essential.
Please see more detailed information on how to comply with this guideline.
Make the Control Text Label and Name the Same
Ensure that the words which visually label a component are also the words associated with the component programmatically.
This helps ensure that people with disabilities can rely on visible labels as a means to interact with the components.
People who operate with voice interaction use the visible labels in their commands.
Please see more detailed information on how to comply with this guideline.
Content Should Not Be Dependent On a User's Ability to Move a Device.
Content should not be dependent on a user's ability to move a device.
Some people cannot hold or move a device steadily.
Ensure that functions triggered by moving a device (for example, shaking or tilting) or by gesturing towards the device can also be operated by more conventional user interface components.
Please see more detailed information on how to comply with this guideline.
Don’t Rely on Dragging for User Interactions
Don’t rely on dragging for user actions.
Some people cannot use a mouse to drag items.
For any action that involves dragging, provide a simple pointer alternative.
Ensure that 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:
tap or click to establish a starting point, then
press and hold that contact while...
performing a repositioning of the pointer, before...
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.
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.
Make Controls Easy to Activate
Some people with physical impairments cannot click small buttons that are close together.
Ensure targets meet a minimum size or have sufficient spacing around them.
The size of the target for pointer inputs is at least 24 by 24 CSS pixels, except where:
Spacing: Undersized targets (those less than 24 by 24 CSS pixels) are positioned so that if a 24 CSS pixel diameter circle is centered on the bounding box of each, the circles do not intersect another target or the circle for another undersized target;
Equivalent: The function can be achieved through a different control on the same page that meets this criterion;
Inline: The target is in a sentence or its size is otherwise constrained by the line-height of non-target text;
User agent control: The size of the target is determined by the user agent and is not modified by the author;
Essential: A particular presentation of the target is essential or is legally required for the information being conveyed.
Ensure that targets can be easily activated without accidentally activating an adjacent target. Users with dexterity limitations and those who have difficulty with fine motor movement find it difficult to accurately activate small targets when there are other targets that are too close.
Providing sufficient size, or sufficient spacing between targets, will reduce the likelihood of accidentally activating the wrong control.
Disabilities addressed by this requirement include hand tremors, spasticity, and quadriplegia. Some people with disabilities use specialized input devices instead of a computer mouse or trackpad.
Typically these types of input device do not provide as much accuracy as mainstream pointing devices. Meeting this requirement also ensures that touchscreen interfaces are easier to use.
WCAG Related Guidelines
2.5.1 Pointer Gestures (Level A)
2.5.2 Pointer Cancellation (Level A)
2.5.4 Motion Actuation (Level A)
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