Tk_Main acts as the main program for most Tk-based applications. Starting with Tk 4.0 it is not called
main anymore because it is part of the Tk library and having a function main in a library (particularly a
shared library) causes problems on many systems. Having main in the Tk library would also make it hard
to use Tk in C++ programs, since C++ programs must have special C++ main functions.
Normally each application contains a small main function that does nothing but invoke Tk_Main. Tk_Main
then does all the work of creating and running a wish-like application.
When it is has finished its own initialization, but before it processes commands, Tk_Main calls the
procedure given by the appInitProc argument. This procedure provides a “hook” for the application to
perform its own initialization, such as defining application-specific commands. The procedure must have
an interface that matches the type Tcl_AppInitProc:
typedef int Tcl_AppInitProc(
Tcl_Interp *interp);
AppInitProc is almost always a pointer to Tcl_AppInit; for more details on this procedure, see the
documentation for Tcl_AppInit.
Tk_Main functions much the same as Tcl_Main. In particular, Tk_Main supports both an interactive mode
and a startup script mode, with the file name and encoding of a startup script under the control of the
Tcl_SetStartupScript and Tcl_GetStartupScript routines. However it calls Tk_MainLoop after processing any
supplied script, and in interactive uses events registered with Tcl_CreateFileHandler to process user
input.