Provided by: tcllib_1.19-dfsg-2_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.
When proposing code changes, please provide unified diffs, i.e the output of diff -u.
Note further that attachments are strongly preferred over inlined patches. Attachments can be made by
going to the Edit form of the ticket immediately after its creation, and then using the left-most button
in the secondary navigation bar.
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>