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intro - introduction to Inferno Tk


This section of the manual provides a reference for the Inferno Tk implementation, which is accessed by Limbo programs via tk(2), and from sh(1) via sh-tk(1).

The following pages were derived by Vita Nuova from documentation that is

Copyright © 1990 The Regents of the University of California
Copyright © 1994-1996 Sun Microsystems, Inc.
See copyright(9) for the full copyright notice.

The format of the pages has changed to follow the format of the rest of this manual, but more important, the content has been changed (typically in small ways) to reflect the variant of Tk implemented by Inferno.

Programming Interface
The interface to Inferno Tk is exclusively through the tk(2) module; all the Tk commands described in this section of the manual are excecuted by passing them as strings to the cmd function in that module. The Inferno Tk implementation is based on the Tk 4.0 documentation, but there are many differences, probably the greatest of which is that there is no associated Tcl implementation, so almost every Inferno application using Tk will need to have some Limbo code associated with it (the sh-tk(1) shell module can also fulful this rôle). See ``An Overview of Limbo/Tk'' in Volume 2 for a tutorial-style introduction to the use of Inferno Tk which summarises the differences from Tk 4.0.

Tk Commands
The command string passed to tk->cmd may contain one or more Tk commands, separated by semicolons. A semicolon is not a command separator when it is nested in braces ({}) or brackets ([]) or it is escaped by a backslash (\). Each command is divided into words: sequences of characters separated by one or more blanks and tabs.

There is also a `super quote' convention: at any point in the command string a single quote mark (') means that the entire rest of the string should be treated as one word.

A word beginning with an opening brace ({) continues until the balancing closing brace (}) is reached. The outer brace characters are stripped. A backslash can be used to escape a brace in this context. Backslash characters not used to escape braces are left unchanged.

A word beginning with an opening bracket ([) continues until the balancing closing bracket (]) is reached. The enclosed string is then evaluated as if it were a command string, and the resulting value is used as the contents of the word.

Single commands are executed in order until they are all done or an error is encountered. By convention, an error is signaled by a return value starting with an exclamation mark (!). The return value from tk->cmd is the return value of the first error-producing command or else the return value of the final single command.

To execute a single command, the first word is examined. It must either begin with dot (.) in which case it must name an existing widget, which will interpret the rest of the command according to its type, or one of the following words, each of which is documented in a manual page of that name in this section:

bind         focus        lower        scrollbar
button       frame        menu         see
canvas       grab         menubutton   send
checkbutton  grid         pack         text
cursor       image        radiobutton  update
destroy      label        raise        variable
entry        listbox      scale

Widget Options
Each manual page in this section documents the options that a particular command will accept. A number of options are common to several of the widgets and are named as ``standard options'' near the beginning of the manual page for each widget. These options are documented in options(9). The types of value required as arguments to options within Inferno Tk are documented under types(9).


options(9), types(9), tk(2), sh-tk(1), tkcmd(1), wmlib(2), draw-intro(2), ``An Overview of Limbo/Tk'' in Volume 2.


The bracket ([]) command interpretation is not applied consistently throughout the Inferno Tk commands (notably, the argument to the send(9) command will not interpret this correctly). Moreover, if the string to be substituted is significantly bigger than the command it was substituting, then it will be truncated.

INTRO(9 ) Rev:  Thu Feb 15 14:44:05 GMT 2007