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+'\"
+'\" Copyright (c) 1990-1994 The Regents of the University of California.
+'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
+'\"
+'\" See the file "license.terms" for information on usage and redistribution
+'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
+'\" 
+'\" SCCS: @(#) bgerror.n 1.5 97/08/04 17:49:35
+'\" 
+.so man.macros
+.TH bgerror n 7.5 Tcl "Tcl Built-In Commands"
+.BS
+'\" Note:  do not modify the .SH NAME line immediately below!
+.SH NAME
+bgerror \- Command invoked to process background errors
+.SH SYNOPSIS
+\fBbgerror \fImessage\fR
+.BE
+
+.SH DESCRIPTION
+.PP
+The \fBbgerror\fR command doesn't exist as built-in part of Tcl.  Instead,
+individual applications or users can define a \fBbgerror\fR
+command (e.g. as a Tcl procedure) if they wish to handle background
+errors.
+.PP
+A background error is one that occurs in an event handler or some
+other command that didn't originate with the application.
+For example, if an error occurs while executing a command specified
+with the \fBafter\fR 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 application can report the error
+in whatever way it wishes.
+When a background error occurs, the unwinding ends in
+the Tcl library and there is no obvious way for Tcl to report
+the error.
+.PP
+When Tcl detects a background error, it saves information about the
+error and invokes the \fBbgerror\fR command later as an idle event handler.
+Before invoking \fBbgerror\fR, Tcl restores the \fBerrorInfo\fR
+and \fBerrorCode\fR variables to their values at the time the
+error occurred, then it invokes \fBbgerror\fR with
+the error message as its only argument.
+Tcl assumes that the application has implemented the \fBbgerror\fR
+command, and that the command will report the error in a way that
+makes sense for the application.  Tcl will ignore any result returned
+by the \fBbgerror\fR command as long as no error is generated.
+.PP
+If another Tcl error occurs within the \fBbgerror\fR command
+(for example, because no \fBbgerror\fR command has been defined)
+then Tcl reports the error itself by writing a message to stderr.
+.PP
+If several background errors accumulate before \fBbgerror\fR
+is invoked to process them, \fBbgerror\fR will be invoked once
+for each error, in the order they occurred.
+However, if \fBbgerror\fR returns with a break exception, then
+any remaining errors are skipped without calling \fBbgerror\fR.
+.PP
+Tcl has no default implementation for \fBbgerror\fR.
+However, in applications using Tk there is a default
+\fBbgerror\fR procedure
+which posts a dialog box containing
+the error message and offers the user a chance to see a stack
+trace showing where the error occurred.
+
+.SH KEYWORDS
+background error, reporting