Momenta’s Command Compass

A Pie Menu By Any Other Name

Does It Offer An Advantage?

Central to the Momenta environment is a unique circular menu called the “Command Compass” that provides users with a consistent, application-independent means of cutting, copying, moving, and otherwise manipulating data. Just about every other graphical user interface from Macintosh to Motif uses standard linear pull-down or pop-up menus to perform these operations. Consequently, the question arises whether the Command Compass really offers any advantage over linear pull-down menus or if it’s just another gimmick.

Pies and Pop-Ups

To consider this question, let’s start with a couple of basic definitions. Conventional linear menus present the user with a list of possible choices from top to bottom. These choices are selected via the mouse or pen, unless the user makes use of a short cut or index. One linear menu may lead to another.

A circular menu like the Command Compass is generally referred to as a “pie menu” because the choices are placed along the circumference of a circle at equal radial distances from the center. When the Command Compass menu is activated, the pen is at the center of the circle (which is inactive) and the options Cut, Move, Menu, Copy, and Undo are provided clockwise on the circumference. To select an option, you simply move the stylus in the appropriate direction. Similar pie menus have been implemented in MIT’s X Window System X10 uwm window manager, Sun’s NeWS Lite Toolkit, OpenWindows for the NeWS Toolkit, and SunView for the SDI game.

Recent Surveys Indicate….

Research has been conducted to examine whether or not circular menus offer any benefits over linear menus. For instance, Jack Callahan, Don Hopkins, Mark Weiser, and Ben Schneiderman presented a paper entitled “An Empirical Comparison of Pie vs. Linear Menus” at the ACM CHI’88 Conference in Washington DC in May, 1988. The researchers ran experiments in a controlled environment to test whether or not pie menus decreased seek time and error rates. Each user manipulated 15 common menus four times — twice with pie menus, twice with linear — for a total of 60 menus. The tests were run on Sun workstations running X Window with a 19-inch bitmapped, high-resolution b/w display and a 3-button optical mouse.

Without going into detail, the results revealed that users using pie menus manipulated display elements faster (as much as 15 percent faster) and with fewer errors than with linear pull-down menus. We’d like to see this experiment repeated with a pen instead of a mouse (that is, using a pen to compare pie and linear menus) and we’d like to see a variation of this experiment run that compares a pen to a mouse.

New Capabilities or Just a Gimmick?

Pie menus provide capabilities that are either untapped or unavailable with linear menus. As Don Hopkins recently pointed out, pie menus can also be two-dimensional in terms of direction and distance. For instance, a font selection pie menu might provide a variety of faces — Helvetica, Roman, Script, etc. These are selected via a directional movement. Once a font is selected, if you keep on moving in that direction, you automatically select the point size — 6, 8, 10, 12, etc. — all in a single movement.

To answer our initial question: Yes, Momenta may be onto something good with its pie menu implementation, which appears to offer some tangible benefits. Momenta’s challenge will be to convince users of the benefits of the Command Compass, which could otherwise be unfairly written off as just another gimmick.

Notes from the Momenta Press Conference As we go to press, Momenta held a lavish extravaganza on both coasts to formally announce its new machine, with company executives jetting from a morning press conference in New York to a similar event in Santa Clara in the afternoon. But glamor and glitz notwithstanding, there seemed to be one noticeable weakness at the event — the lack of third party software. The only announced third party applications were Rupp Technology’s (Phoenix, AZ) Stylus WP word processing program and Penware’s (San Jose, CA) PenCell spreadsheet. If Momenta’s Command Compass and MOVE are to succeed, they need the support of third party software developers. Otherwise, Momenta will be just another hardware platform for PenWindows.