diff -u -r -N ctk4.0b1/library/bgerror.tcl ctk4.2b1/library/bgerror.tcl
--- ctk4.0b1/library/bgerror.tcl	Wed Dec 31 21:00:00 1969
+++ ctk4.2b1/library/bgerror.tcl	Wed Sep 18 18:38:29 1996
@@ -0,0 +1,74 @@
+# bgerror.tcl --
+#
+# This file contains a default version of the bgerror procedure.  It
+# posts a dialog box with the error message and gives the user a chance
+# to see a more detailed stack trace.
+#
+# SCCS: @(#) bgerror.tcl 1.9 96/05/02 10:17:11
+#
+# Copyright (c) 1992-1994 The Regents of the University of California.
+# Copyright (c) 1994-1995 Sun Microsystems, Inc.
+#
+# See the file "license.terms" for information on usage and redistribution
+# of this file, and for a DISCLAIMER OF ALL WARRANTIES.
+
+# The following declaration servers no purpose other than to generate
+# a tclIndex entry for "tkerror".  Since tkerror and bgerror are hard-wired
+# by the Tcl interpreter to be synonyms, the definition of tkerror is
+# immediately overridden when bgerror is defined.
+
+proc tkerror {} {}
+
+# bgerror --
+# This is the default version of bgerror.  It posts a dialog box containing
+# the error message and gives the user a chance to ask to see a stack
+# trace.
+# Arguments:
+# err -			The error message.
+
+proc bgerror err {
+    global errorInfo
+    set info $errorInfo
+    set button [tk_dialog .bgerrorDialog "Error in Tcl Script" \
+	    "Error: $err" error 0 OK "Skip Messages" "Stack Trace"]
+    if {$button == 0} {
+	return
+    } elseif {$button == 1} {
+	return -code break
+    }
+
+    set w .bgerrorTrace
+    catch {destroy $w}
+    toplevel $w -class ErrorTrace
+    wm minsize $w 1 1
+    wm title $w "Stack Trace for Error"
+    wm iconname $w "Stack Trace"
+    button $w.ok -text OK -command "destroy $w"
+    text $w.text -relief sunken -bd 2 -yscrollcommand "$w.scroll set" \
+	    -setgrid true -width 60 -height 20
+    scrollbar $w.scroll -relief sunken -command "$w.text yview"
+    pack $w.ok -side bottom -padx 3m -pady 2m
+    pack $w.scroll -side right -fill y
+    pack $w.text -side left -expand yes -fill both
+    $w.text insert 0.0 $info
+    $w.text mark set insert 0.0
+
+    # Center the window on the screen.
+
+    wm withdraw $w
+    update idletasks
+    set x [expr [winfo screenwidth $w]/2 - [winfo reqwidth $w]/2 \
+	    - [winfo vrootx [winfo parent $w]]]
+    set y [expr [winfo screenheight $w]/2 - [winfo reqheight $w]/2 \
+	    - [winfo vrooty [winfo parent $w]]]
+    wm geom $w +$x+$y
+    wm deiconify $w
+
+    # Be sure to release any grabs that might be present on the
+    # screen, since they could make it impossible for the user
+    # to interact with the stack trace.
+
+    if {[grab current .] != ""} {
+	grab release [grab current .]
+    }
+}
