NAME
       tkerror - Command invoked to process background errors

SYNOPSIS
       tkerror message


DESCRIPTION
       The  tkerror command doesn't exist as built-in part of Tk.
       Instead, individual applications or  users  can  define  a
       tkerror  command (e.g. as a Tcl procedure) if they wish to
       handle background errors.

       A background error is one that occurs in  a  command  that
       didn't originate with the application.  For example, if an
       error occurs while executing a command  specified  with  a
       bind of after command, then it is a background error.  For
       a non-background error, the error can simply  be  returned
       up through nested Tcl command evaluations until it reaches
       the top-level code in the application; then  the  applica-
       tion can report the error in whatever way it wishes.  When
       a background error occurs, the unwinding ends  in  the  Tk
       library  and  there is no obvious way for Tk to report the
       error.

       When Tk detects a background error, it invokes the tkerror
       command,  passing  it  the error message as its only argu-
       ment.  Tk assumes that the application has implemented the
       tkerror  command,  and  that  the  command will report the
       error in a way that makes sense for the  application.   Tk
       will ignore any result returned by the tkerror command.

       If  another  Tcl  error  occurs within the tkerror command
       then Tk reports the error itself by writing a  message  to
       stderr.

       The Tk script library includes a default tkerror procedure
       that posts a dialog box containing the error  message  and
       offers  the  user a chance to see a stack trace that shows
       where the error occurred.


KEYWORDS
       background error, reporting
