


uevent(n)                  User events                  uevent(n)


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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

_________________________________________________________________

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 widgets.
       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 combi-
              nation, 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.





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uevent(n)                  User events                  uevent(n)


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 genera-
       tor 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 com-
              mands 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 agree-
              ment  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 system 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.  Specify-
              ing  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



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uevent(n)                  User events                  uevent(n)


              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://source-
       forge.net/tracker/?group_id=12883].  Please also report any  ideas  for
       enhancements you may have for either package and/or documentation.

KEYWORDS
       bind, event, generate event, unbind

CATEGORY
       Programming tools

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






































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