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tcl::chan::events(n) 1 tcllib "Reflected/virtual channel support"


tcl::chan::events - Event support for reflected/virtual channels

Table Of Contents


  • package require Tcl 8.5
  • package require TclOO
  • package require tcl::chan::core ?1?
  • package require tcl::chan::events ?1?


The tcl::chan::events package provides a TclOO class implementing common behaviour needed by virtually every reflected or virtual channel supporting event driven IO. It is a sub-class of tcl::chan::core, inheriting all of its behaviour.

This class expects to be used as either superclass of a concrete channel class, or to be mixed into such a class.

Class API

::tcl::chan::events objectName

This command creates a new channel event core object with an associated global Tcl command whose name is objectName. This command may be used to invoke various operations on the object, as described in the section for the Instance API.

Instance API

The API of channel event core instances provides only four methods, two corresponding to channel handler commands (For reference see TIP 219), and the other two for use by sub-classes to control event generation. They former expect to be called from whichever object instance the channel event core was made a part of.

objectName finalize thechannel

This method implements standard behaviour for the finalize method of channel handlers. It overrides the behaviour inherited from tcl::chan::core and additionally disables any and all event generation before destroying itself.

objectName watch thechannel eventmask

This method implements standard behaviour for the watch method of channel handlers. Called by the IO system whenever the interest in event changes it updates the instance state to activate and/or suppress the generation of the events of (non-)interest.

objectName allow eventname...
objectName disallow eventname...

These two methods are exported to sub-classes, so that their instances can notify their event core of the events the channel they implement can (allow) or cannot (disallow) generate. Together with the information about the events requested by Tcl's IO system coming in through the watch method the event core is able to determine which events it should (not) generate and act accordingly.

Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category virtchannel of the Tcllib Trackers. 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.


event management, reflected channel, tip 219, virtual channel