About keyed lists and the callback structure (cbs)

The cbs uses a special format called a keyed list. Keyed lists are very similar to structures found in C programming. In a keyed list, you access data by referencing fields, or ``keys''.

For instance, the key that you would reference to obtain the handle of the widget that called the callback is widget; the key that you would reference to get the handle of the dialog the widget is on is dialog.

SCO Visual Tcl provides commands to delete, get, list, and set keyed list items:

• keyldel(TCL)

• keylget(TCL)

• keylkeys(TCL)

• keylset(TCL)

Here is an example of using cbs in the Kill program:

cbs is tacked onto the end of the callback's parameter list. cbs must be declared when defining callback procedures.