\c{

The $hypertext$ widget

Both the Tk canvas and text widget allow the binding of actions to particular items and hence defining dynamically what we may call hyperstructures. A different, in a way more static, approach is offered by the hypertext widget originally developed by George Howlett. %%george.howlett@att.com. } .so sli-help \c{ The hypertext widget may be used to display text files containing embedded Tcl code. The Tcl code must be placed between escapes, that take the form of {\tt %%} for both the start and end of the code. A screen shot of a fragment of the online help for drawtool is given in slide hyper. Notice that the online help provides a replica of the drawtool application, surrounded by text. When looking at (again a fragment of) the hypertext file specifying the contents of the online help, given in slide help-text, you see that the drawtool command defined in section new is employed to create the embedded widget. } \c{ When specifying the hypertext file, widgets may be given a pathname relative to the pathname of the hypertext widget by using the variable this. In addition, the hypertext widget offers the variables thisline and thisfile to identify the current line number and current file name. } \c{ Any of the widgets and commands offered by Tcl/Tk or supported by hush may be included in a hypertext file, including the ones defined by the program itself. }