Tk_EventInit - Use the Tk event loop without the rest of Tk
This procedure may be invoked to use the Tk event management functions without the rest of Tk (e.g., in applications that do not have access to a display). Tk_EventInit creates the after and fileevent commands in interp. It also creates versions of the tkwait and update commands with reduced functionality: the tkwait command supports only the variable option, not visibility or $widget, and update does not check for X events. Tk_EventInit always returns TCL_OK to signal that it completed successfully.
The event-management procedures in Tk are divided into two groups, those that can be used stand-alone and those that require the full Tk library to be present. The following procedures may be used stand-alone: Tk_CreateFileHandler, Tk_CreateFileHandler2, Tk_DeleteFileHandler, Tk_CreateTimerHandler, Tk_DeleteTimerHandler, Tk_DoWhenIdle, Tk_CancelIdleCall, Tk_DoOneEvent, Tk_Sleep, and Tk_BackgroundError. Note that Tk_MainLoop cannot be used without the full Tk library, since it checks to see if windows are still open. If an application uses the event procedures stand-alone, it must include its own main loop that invokes Tk_DoOneEvent repeatedly.
Tk_EventInit is typically called from an application's Tcl_AppInit procedure; it should not be invoked in applications that use the full Tk library (e.g., those that have already invoked Tk_CreateMainWindow). However, it is OK for an application to start up using Tk_EventInit, compute without X for a while, and later invoke Tk_CreateMainWindow. When Tk_CreateMainWindow is invoked, the full suite of windowing Tcl commands will become available, and the full-blown versions of tkwait and update will replace the abridged versions created with Tk_EventInit.
event management, Tcl_AppInit