Level A
For functionality that can be operated using a single pointer, at least one of the following is true:
- No Down-Event: The down-event of the pointer is not used to execute any part of the function;
- 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;
- Up Reversal: The up-event reverses any outcome of the preceding down-event;
- Essential: Completing the function on the down-event is essential.>
Explanation
For custom touch gestures that use a single finger, at least one of these things must be true:
- The action is not triggered on a down event (when the finger touches the control);
- The action is triggered on an up event (when the finger is lifted from the control), and there is a way to abort or undo the action;
- The up event reverses what happens on the down event;
- It is essential that the action be triggered on a down event.
This makes sure that people with dexterity and mobility difficulties do not accidentally trigger actions, and when they do they have a way to undo it.
Roles
- Design
- Development
- QA
Requirements
- Custom gestures are triggered on the up event; or
- A way is provided for people to abort the action, like a confirmation dialogue; or
- Custom gestures use techniques like press and hold, so that the action triggered by the down event is reversed on the up event; or
- The action must be triggered on the down event because it is essential it happens this way.
Common mistakes
- An action that could be triggered on the up event, is triggered on the down event;
- An action is triggered on the up event, but there is no way for it to be aborted or undone;
- An action is triggered whilst a down event is in progress, but not reversed when the up event happens.
Official resources
- 2.5.2 Pointer Cancellation
- Understanding 2.5.2 Pointer Cancellations
- How to meet 2.5.2 Pointer Cancellation