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markom |
'\"
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'\" Copyright (c) 1992-1994 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" RCS: @(#) $Id: BackgdErr.3,v 1.1.1.1 2002-01-16 10:25:23 markom Exp $
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'\"
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.so man.macros
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.TH Tcl_BackgroundError 3 7.5 Tcl "Tcl Library Procedures"
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.BS
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.SH NAME
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Tcl_BackgroundError \- report Tcl error that occurred in background processing
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.SH SYNOPSIS
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.nf
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\fB#include \fR
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.sp
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\fBTcl_BackgroundError\fR(\fIinterp\fR)
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.SH ARGUMENTS
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.AS Tcl_Interp *interp
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.AP Tcl_Interp *interp in
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Interpreter in which the error occurred.
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.BE
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.SH DESCRIPTION
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.PP
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This procedure is typically invoked when a Tcl error occurs during
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``background processing'' such as executing an event handler.
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When such an error occurs, the error condition is reported to Tcl
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or to a widget or some other C code, and there is not usually any
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obvious way for that code to report the error to the user.
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In these cases the code calls \fBTcl_BackgroundError\fR with an
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\fIinterp\fR argument identifying the interpreter in which the
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error occurred. At the time \fBTcl_BackgroundError\fR is invoked,
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\fIinterp->result\fR is expected to contain an error message.
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\fBTcl_BackgroundError\fR will invoke the \fBbgerror\fR
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Tcl command to report the error in an application-specific fashion.
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If no \fBbgerror\fR command exists, or if it returns with an error condition,
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then \fBTcl_BackgroundError\fR reports the error itself by printing
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a message on the standard error file.
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.PP
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\fBTcl_BackgroundError\fR does not invoke \fBbgerror\fR immediately
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because this could potentially interfere with scripts that are in process
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at the time the error occurred.
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Instead, it invokes \fBbgerror\fR later as an idle callback.
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\fBTcl_BackgroundError\fR saves the values of the \fBerrorInfo\fR and
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\fBerrorCode\fR variables and restores these values just before
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invoking \fBbgerror\fR.
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.PP
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It is possible for many background errors to accumulate before
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\fBbgerror\fR is invoked. When this happens, each of the errors
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is processed in order. However, if \fBbgerror\fR returns a
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break exception, then all remaining error reports for the
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interpreter are skipped.
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.SH KEYWORDS
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background, bgerror, error
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