Users with various disabilities and limitations may be more prone to accidentally initiating a function they didn’t intend to when using their pointers. With that in mind, the fine folks at WCAG have suggested that, for functionality that’s operated using a single pointer—such as single or double taps and clicks, long presses, or path-based gestures—one of the following is true:
It’ll be easier and more accessible for users to undo or cancel an action if that function is activated with an up-event. The standard mouse click or finger tap has a built-in method for cancelling the action. If a user presses down on an object, and then realizes they selected the wrong thing, they can move the pointer away from the object and then release it, stopping the function from initiating.
The abort and undo functions become even more crucial with complex functions. Drag-and-drop, for instance, involves multiple actions, including both down and up-events, thus increasing the chance of user error. First, a user presses down on an object (the down-event), then moves the object to the necessary location, and finally releases it to complete the function (the up-event). In such a situation, it might be a good idea to ask users to confirm the move through a dialog box or include an undo button. Users may also be able to effectively cancel the function by moving the object back to its original location or to someplace on the screen that disallows a move before releasing it.