Flexible Input
Interactive elements can always be operated with pointer devices (mouse, eye-tracker, etc.) as well as with a keyboard.
Complementary to the requirement for flexible output options, flexible input options are required.
This is very straight forward: All interactive components of user interfaces must be accessible and operable via pointer devices as well as serial input devices.
The computer mouse is representative of pointer devices such as trackpads, trackballs and others such as mouth mice, joysticks or eye-tracking devices.
The keyboard, on the other hand, represents a wide range of devices for serial navigation. Here, the user moves serially from interactive element to interactive element by pressing a key (e.g. tab key) and triggers the desired element with another key (e.g. enter / space bar). Serial input devices are often integrated into custom-made environmental control devices for people with severe motor impairments. (e.g. quadriplegics).
Electronic user interfaces should always be usable by means of both pointer and serial input devices.
Sequential navigation can only work if the keyboard focus is clearly visible at all times!
Flexible input test procedure
Keyboard operability
- Put aside the computer mouse and try to use the full functionality of a digital user interface with the keyboard alone.
- If there are no other instructions that are visible to everyone, only Tab, Enter, Space, Arrow keys and Esc are used.
Technical focusability
Particular attention is given to buttons, which are often inaccessible to focus because they aren’t recognized as actual buttons, as well as overlays, pop-up windows, and expandable elements, which frequently fail to receive focus after being opened due to their technical position not aligning with their visual appearance.
Note to Mac users
For Mac users it is important to explicitly enable keyboard navigation for testing keyboard operability (flexible input): How to on external page Deque university
Focus visibility and tab order
A distinction should be made to interactive elements that are technically accessible, but where it’s not obvious that they have focus. For sighted keyboard users, it’s not useful if they can navigate the content with the keyboard but can’t tell where the keyboard focus is located. The keyboard focus must always be clearly visible and focus order must be predictable.