Provided by: tcllib_1.17-dfsg-1_all 
NAME
uevent - User events
SYNOPSIS
package require Tcl 8.4
package require uevent ?0.3.1?
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
::uevent::watch::tag::add pattern command
{*}command bound tag
{*}command unbound tag
::uevent::watch::tag::remove token
::uevent::watch::event::add tag_pattern event_pattern command
{*}command bound tag event
{*}command unbound tag event
::uevent::watch::event::remove token
_________________________________________________________________________________________________
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 eight commands, as specified below. Note that when the package is used
from within Tcl 8.5+ all the higher commands are ensembles, i.e. the :: separators can be
replaceed by spaces.
::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.
::uevent::watch::tag::add pattern command
This command sets up a sort of reverse events. Events generated, i.e. the command
prefix invoked, when observers bind to and unbind from specific tags.
Note that the command prefix is only invoked twice per tag, first when the first
command is bound to any event of the tag, and second when the last command bound to
the tag is removed.
The signature of the command prefix is
{*}command bound tag
{*}command unbound tag
The result of the command is a token representing the watcher.
::uevent::watch::tag::remove token
This command removes a watcher for (un)bind events on tags.
The result of the command is the empty string.
::uevent::watch::event::add tag_pattern event_pattern command
This command sets up a sort of reverse events. Events generated, i.e. the command
prefix invoked, when observers bind to and unbind from specific combinations of
tags and events.
Note that the command prefix is only invoked twice per tag/event combination, first
when the first command is bound to it, and second when the last command bound to
the it is removed.
The signature of the command prefix is
{*}command bound tag event
{*}command unbound tag event
The result of the command is a token representing the watcher.
::uevent::watch::event::remove token
This command removes a watcher for (un)bind events on tag/event combinations.
The result of the command is the empty string.
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 Trackers
[http://core.tcl.tk/tcllib/reportlist]. 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) 2007-2012 Andreas Kupries <andreas_kupries@users.sourceforge.net>