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

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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 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
              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 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 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://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(n)

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(n)
