context menu

Touch interfaces are increasing in popularity and ubiquity since the introduction of the iPhone and other mobile devices. Touch screens deliver a larger interactive surface and direct manipulation of the user interface to users. The direct manipulation leads to an intuitive interaction experience, but the touch has a particular Achille's Heel that the mouse doesn't suffer from - the user's finger is blocking their view of the screen.

There are several methods for addressing this difficulty, some of which are employed currently on touch-enabled phones. The iPhone, for example, will popup hints when you hold your finger over a letter on the keyboard or on a link on a webpage. However, this interaction is used sparingly. In the presentation of the new Palm WebOS the application menu bar "Wave" is drawn just above the user's finger so the user can see what they are selecting.

Context menus are a particular case in which the touch interface obscures the data being selected. Context menus also suffer from a typical problem in the transition from large, high-resolution desktop displays to a mobile device - they are too large and rely on vertical scrolling. Hierarchical context menus particularly aggravate this situation by requiring more vertical scrolling.

A better context menu could be based on a radial popup menu. The available options could popup in a circle around the user's finger. This allows all of the options to be visible at once, and the user can move their finger horizontally and vertically to make a selection. The interface can register a selection based on the direction of the user's finger, whether or not the finger is actually hovering over a menu item. This allows the user to move their finger outside of the radius of the context menu and make a selection without obscuring the text describing the function.

Hierarchical context menus can be implemented similarly with successive levels of detail opening out of the radial menu when the user moves their finger over that section of the menu. The speed of opening the hierarchy must be closely controlled and adjusted based on user tests to keep users from making unintentional selections.

Canceling the selection can be facilitated by the user moving their finger back to the center position that originally initiated the context menu.