uevent(3tcl)							    User events 						      uevent(3tcl)

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NAME

       uevent - User events

SYNOPSIS

       package require Tcl  8.4

       package require uevent  ?0.2?

       package require logger

       ::uevent::bind tag event command

       command tag event details

       ::uevent::unbind token

       ::uevent::generate tag event ?details?

       ::uevent::list

       ::uevent::list tag

       ::uevent::list tag event

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DESCRIPTION

       This  package  provides a general facility for the handling of user events. Allows the binding of arbitrary commands to arbitrary events on
       arbitrary tags, removal of bindings, and event generation.

       The main difference to the event system built into the Tcl/Tk core is that the latter can generate only virtual events, and only  for  wid-
       gets.  It  is not possible to use the builtin facilities to bind to events on arbitrary (pseudo-)objects, nor is it able to generate events
       for such.

       Here we can, by assuming that each object in question is represented by its own tag. Which is possible as we allow arbitrary tags.

       More differences:

       [1]    The package uses only a two-level hierarchy, tags and events, to handle everything, whereas the Tcl/Tk  system  uses  three  levels,
	      i.e.  objects, tags, and events, with a n:m relationship between objects and tags.

       [2]    This package triggers all bound commands for a tag/event combination, and they are independent of each other. A bound command cannot
	      force the event processing core to abort the processing of command coming after it.

API

       The package exports three commands, as specified below:

       ::uevent::bind tag event command
	      Using this command registers the command prefix to be triggered when the event occurs for the tag. The result of the command  is	an
	      opaque  token  representing  the	binding.  Note that if the same combination of <tag,event,command> is used multiple times the same
	      token is returned by every call.

	      The signature of the command prefix is

	      command tag event details

       where details contains the argument(s) of the event. Its contents are event specific and have to be agreed upon between actual event gener-
       ator and consumer. This package simply transfers the information and does not perform any processing beyond that.

       ::uevent::unbind token
	      This  command  releases  the event binding represented by the token. The token has to be the result of a call to ::uevent::bind. The
	      result of the command is the empty string.

       ::uevent::generate tag event ?details?
	      This command generates an event for the tag, triggering all commands bound to that  combination.	The  details  argument	is  simply
	      passed unchanged to all event handlers. It is the responsibility of the code generating and consuming the event to have an agreement
	      about the format and contents of the information carried therein. The result of the command is the empty string.

	      Note that all bound commands are triggered, independently of each other. The event handlers cannot assume a specific order. They are
	      also  not called synchronously with the invokation of this command, but simply put into the event queue for processing when the sys-
	      tem returns to the event loop.

	      Generating an event for an unknown tag, or for a <tag,event> combination which has no commands bound to it is  allowed,  such  calls
	      will be ignored.

       ::uevent::list
	      In this form the command returns a list containing the names of all tags which have events with commands bound to them.

       ::uevent::list tag
	      In  this format the command returns a list containing the names of all events for the tag with commands bound to them. Specifying an
	      unknown tag, i.e. a tag without event and commands, will cause the command to throw an error.

       ::uevent::list tag event
	      In this format the command returns a list containing all commands bound to the event for the  tag.  Specifying  an  unknown  tag	or
	      unknown event, will cause the command to throw an error.

BUGS, IDEAS, FEEDBACK
       This  document,	and the package it describes, will undoubtedly contain bugs and other problems.  Please report such in the category uevent
       of the Tcllib SF Trackers [http://sourceforge.net/tracker/?group_id=12883].  Please also report any ideas for enhancements you may have for
       either package and/or documentation.

SEE ALSO

       hook(3tcl)

KEYWORDS

       bind, event, generate event, hook, unbind

CATEGORY

       Programming tools

COPYRIGHT

       Copyright (c) 2007 Andreas Kupries <andreas_kupries@users.sourceforge.net>

uev									0.2							      uevent(3tcl)