uevent(3tcl) User events uevent(3tcl) 







uevent - User events








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












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.










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

  







  

  






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.

  










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.








hook(3tcl)








bind, event, generate event, hook, unbind








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Copyright (c) 2007-2012 Andreas Kupries <andreas_kupries@users.sourceforge.net>








  

    0.3.1
    tcllib