Tk Built-In Commands - listener manual page

## listener

Create and manipulate listener widgets

### SYNOPSIS

(listener widget-name ?options?)

### WIDGET-SPECIFIC OPTIONS

Name:
Class:
Option keyword: :command
STklos slot name: command
  Specifies a STk procedure to associate with the listener. This procedure is invoked when a complete s-expr is entered in the listener. This s-expr is passed as a string to the procedure. The procedure must return the string which will be inserted in response to the s-expr input. The default procedure is the Identity procdure.

Name:
Class:
Option keyword: :output-color
STklos slot name: output-color
  Specifies the color used the output lines

Name:
Class:
Option keyword: :prompt-color
STklos slot name: prompt-color
  Specifies the color used for the prompt

Name:
Class:
Option keyword: :prompt
STklos slot name: prompt
  Specifies the prompt used for reading s-expr. Defaults to "> "

### DESCRIPTION

The listener procedure creates a new text window (given by the widget-name argument) and associates it bindiangs suitable for a listener. Since a listener is in fact a text widget, all the options of text are applicable to a listener. The listener procedure returns its widget-name argument. At the time this procedure is invoked, there must not exist a window named widget-name, but widget-name's parent must exist.

A listener is a widget for doing interactive I/O. Typical usage for this widget consists of a text window whose inputs are sent to the Scheme evaluator and whose result is displayed in the listener. An example for this is shown at the end of this page.

### WIDGET PROCEDURE

All the text procedure are avialble for a listener, plus

(listener-insert-string widget-name str)
  inserts the string str just before the input prompt.

### EXAMPLE

Hereafter is a simple use of the listener widget which interact with the evaluator.

    (listener '.t :width   50
                  :height  10
                  :command (lambda (x)
                             (eval-string x (global-environment))))
    (pack .t)

### DEFAULT BINDINGS

The defaults bindings are identical to the text bindings.

### SEE ALSO

text

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