Our program is starting to get quite sophisticated, allowing ideas to be created and moved around on multiple screens, displaying different users' ideas in different colors, responding to new and leaving users, updating latecomers to the conference, and even persisting when all users have left the conference.
As a conference participant, you may sometimes find it hard to follow when several people are working at the same time. Ideas are being rapidly moved around, and its unclear who's doing what when. Also, because the canvas is quite tall, it can become hard to track where people are working.
GroupKit provides a number of different awareness widgets to help with these sorts of problems. Keeping track of where people are working and what they are doing is a common problem in a number of different groupware programs, so our widgets can be easily added to many different applications.
Telepointers, also known as multiple cursors, are used to provide very fine-grained information about where other users are working in the application. As other users move around the application, you'll see a small cursor which follows their mouse cursor. Just tracking those cursors - which you're usually just peripherally aware of - provides a surprising amount of information about who's doing what in an application, what objects people are working with, and how active different people are (Figure XX). Telepointers can be attached to any Tk widget.
Figure XX. GroupKit's telepointers.
Adding telepointers to our example is quite straightforward, requiring only one line of code.gk::telepointers attach .notepad
Figure XX illustrates GroupKit's multi-user scrollbars. They consist of two parts: a conventional Tk scrollbar on the right, and a set of bars showing where users are located in a document to its left. The conventional scrollbar is used normally, to scroll your own view in the document. As you scroll, you'll also notice one of the bars to the left scrolling with you. That bar is showing your position in the document. As other users scroll their own views, the other bars on their display will change to show their new positions. Clicking on each bar will display a popup reminding you which user the bar is associated with. Multi-user scrollbars allow you to quickly find where others are working in a large document and - by aligning your view with theirs - join them.
Figure XX. Multi-user scrollbars.
Multi-user scrollbars are added to applications in exactly the same way that conventional scrollbars are. In fact, the only difference is that instead of using the Tk scrollbar command, you use the GroupKit gk::scrollbar command.
proc buildWindow {} {
...
gk::scrollbar .scroll -command ".notepad yview"
...
}
GroupKit also comes with a number of other widgets. You've already seen
the menubar, which includes items such as an Exit command, an about box for
GroupKit, and an item which brings up a dialog box giving you information
about the different users in the conference with you. There's also a widget
called the "radar", which is similar to the multi-user scrollbar, but
augments location information with a two-dimensional miniature of the
entire document.There's also a widget that is included to make
it easier to build online help into your application.
At this point we've completed our Note Organizer program; you'll find the complete program listing at the end of this chapter. The next section will go on to talk about a very different approach to building groupware applications with GroupKit.