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uevent(n)                                        User events                                       uevent(n)



____________________________________________________________________________________________________________

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 arbi-trary arbitrary
       trary 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  possi-ble possible
       ble 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 generator and consumer. This package simply transfers the informa-tion information
       tion 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 combina-tion. combination.
              tion. The details argument is simply passed unchanged to all event handlers. It is the respon-sibility responsibility
              sibility  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 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. 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://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>




uev                                                  0.2                                           uevent(n)