Single Display Groupware
using one computer with multiple input devices connected, sharing the same output display

Single Display Groupware (SDG) is a class of CSCW applications that deals with several users working co-located, using one computer, in which multiple input devices are connected, and sharing the same output display. There are several issues in developing SDG applications, most of them related to the poor or lack of support in operating systems and programming languages to aid the development of multiple users systems. Most existing operating systems and applications provide support for only a single user to interact with it at a time and recognize input from unique devices only, for example the user is clicking or moving a mouse or typing on the keyboard. Programming languages also provide poor support for the development of multiple users applications and interfaces. The interface components or widgets provided by these languages, such as menus, dialog boxes, and toolboxes, are also not designed to recognize and to appropriately respond to input from several users and devices simultaneously. Therefore, being able to develop adequate SDG applications in a quick and easy way is a serious challenge.

Our research concentrates on studying the design of interface widgets for SDG. At this moment we are interested in analyzing interface widgets in terms of the level the interference they may cause users of the applications. More specifically, we are analyzing the use of transparent popup menus and comparing their usage to that of opaque menus and a single user situation.

The figure shows a screen of a simple SDG editor. There are four users drawing, as we can see their cursors on the screen. The user on the right side of the screen is drawing a rectangle in green while the other 2 (in the middle and on the top left corner) are scribbling in red. The fourth user is making a colour selection at the toolbox at the left side of the window. This is a multiple selection toolbox, from which the users can make their own mode selections simultaneously. The menus are still the classical pull down menus but the system is being modified in order to offer popup menus for mode selection.

Primary Investigators

Ana Zanella
Saul Greenberg (Supervisor)


  • We are currently testing the use of popup menus for SDG applications. We designed a user test in which one user plays a "connect the dots" game and a second user tries to slow him down by popping up menus on the screen.
  • We are comparing the user's performance when using semi-transparent and opaque popup menus. Other issues such as user identification, awareness, interference and personal vs. public actions will also be studied on the context of this research.

Current Status

This research is in early stage. The results of the test with transparent popup menus will lead us to the design of other widgets, such as menus, message boxes, toolboxes, etc.

Key Papers

  • Zanella, A. and Greenberg, S. (2000) A Single Display Groupware Widget Set. In Proceedings of the Western Computer Graphics Symposium 2000, (Panorama Mountain Village, BC, Canada), March 26-29, 2000. [PDF]