Tk::callbacks man page on Kali

Man page or keyword search:  
man Server   9211 pages
apropos Keyword Search (all sections)
Output format
Kali logo
[printable version]

callbacks(3pm)	      User Contributed Perl Documentation	callbacks(3pm)

NAME
       Tk::callbacks - Specifying code for Tk to call.

SYNOPSIS
       One can specify a callback in one of the following ways:

       Without arguments:

	   ... => \&subname, ...
	   ... => sub { ... }, ...
	   ... => 'methodname', ...

       or with arguments:

	   ... => [ \&subname, args ... ], ...
	   ... => [ sub { ... }, args... ], ...
	   ... => [ 'methodname', args... ], ...

DESCRIPTION
       Perl/Tk has a callback, where Tcl/Tk has a command string (i.e. a
       fragment of Tcl to be executed).	 A perl/Tk callback can take one of
       the following basic forms:

       ·   Reference to a subroutine "\&subname"

       ·   Anonymous subroutine (closure) "sub { ... }"

       ·   A method name 'methodname'

       Any of these can be provided with arguments by enclosing them and the
       arguments in []. Here are some examples:

       $mw->bind($class, "<Delete>" => 'Delete');

       This will call $widget->Delete, the $widget being provided (by bind) as
       the one where the Delete key was pressed.

       While having bind provide a widget object for you is ideal in many
       cases it can be irritating in others. Using the list form this
       behaviour can be modified:

       $a->bind("<Delete>",[$b => 'Delete']);

       because the first element $b is an object bind will call $b->Delete.

       Note that method/object ordering only matters for "bind" callbacks, the
       auto-quoting in perl5.001 makes the first of these a little more
       readable:

	   $w->configure(-yscrollcommand => [ set => $ysb]);
	   $w->configure(-yscrollcommand => [ $ysb => 'set' ]);

       but both will call $ysb->set(args provided by Tk)

       Another use of arguments allows you to write generalized methods which
       are easier to re-use:

	   $a->bind("<Next>",['Next','Page']);
	   $a->bind("<Down>",['Next','Line']);

       This will call $a->Next('Page') or $a->Next('Line') respectively.

       Note that the contents of the "[]" are evaluated by perl when the
       callback is created. It is often desirable for the arguments provided
       to the callback to depend on the details of the event which caused it
       to be executed. To allow for this callbacks can be nested using the
       "Ev(...)" "constructor".	 "Ev(...)" inserts callback objects into the
       argument list. When perl/Tk glue code is preparing the argument list
       for the callback it is about to call it spots these special objects and
       recursively applies the callback process to them.

EXAMPLES
	   $entry->bind('<Return>' => [$w , 'validate', Ev(['get'])]);

	   $toplevel->bind('all', '<Visibility>', [\&unobscure, Ev('s')]);

	   $mw->bind($class, '<Down>', ['SetCursor', Ev('UpDownLine',1)]);

SEE ALSO
       Tk::bind Tk::after Tk::options Tk::fileevent

KEYWORDS
       callback, closure, anonymous subroutine, bind

perl v5.26.0			  2017-07-22			callbacks(3pm)
[top]

List of man pages available for Kali

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net