# Class Uq_tcl.tcl_event_system

    class tcl_event_system : ?run:runner -> unit -> Unixqueue.event_system

This class is an alternate implementation of the Unixqueue event systems for the TCL event loop. Use this class instead of `unix_event_system`.

Both Unixqueue and TCL provide event queues for system events, and it is possible to merge both queues such that events may happen and be processed on one queue while the other queue blocks.

To achieve this, just use this class instead of `unix_event_system`. It automatically creates handlers for the TCL loop when necessary. However, you must not invoke the method `run`, as this class does not provide its own event loop. Instead, ensure that `Tk.mainLoop` is called.

Of course, this is all intended to help writing applications which have a graphical user interface (GUI) built with labltk, and some network functionality which is designed to work in the background. Simply create your GUI with labltk, and after the button is pressed which starts the network I/O, you add resources to this event queue, and the I/O will be processed concurrently with any user input coming from the GUI.

Note: The implementation is not thread-safe (and neither TCL).