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Diffstat (limited to 'tcl8.6/doc/BackgdErr.3')
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diff --git a/tcl8.6/doc/BackgdErr.3 b/tcl8.6/doc/BackgdErr.3 new file mode 100644 index 0000000..adbe33c --- /dev/null +++ b/tcl8.6/doc/BackgdErr.3 @@ -0,0 +1,78 @@ +'\" +'\" Copyright (c) 1992-1994 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. +'\" +.TH Tcl_BackgroundError 3 7.5 Tcl "Tcl Library Procedures" +.so man.macros +.BS +.SH NAME +Tcl_BackgroundException, Tcl_BackgroundError \- report Tcl exception that occurred in background processing +.SH SYNOPSIS +.nf +\fB#include <tcl.h>\fR +.sp +\fBTcl_BackgroundException\fR(\fIinterp, code\fR) +.sp +\fBTcl_BackgroundError\fR(\fIinterp\fR) +.SH ARGUMENTS +.AS Tcl_Interp *interp +.AP Tcl_Interp *interp in +Interpreter in which the exception occurred. +.AP int code in +The exceptional return code to be reported. +.BE + +.SH DESCRIPTION +.PP +This procedure is typically invoked when a Tcl exception (any +return code other than TCL_OK) occurs during +.QW "background processing" +such as executing an event handler. +When such an exception occurs, the condition is reported to Tcl +or to a widget or some other C code, and there is not usually any +obvious way for that code to report the exception to the user. +In these cases the code calls \fBTcl_BackgroundException\fR with an +\fIinterp\fR argument identifying the interpreter in which the +exception occurred, and a \fIcode\fR argument holding the return +code value of the exception. The state of the interpreter, including +any error message in the interpreter result, and the values of +any entries in the return options dictionary, is captured and +saved. \fBTcl_BackgroundException\fR then arranges for the event +loop to invoke at some later time the command registered +in that interpreter to handle background errors by the +\fBinterp bgerror\fR command, passing the captured values as +arguments. +The registered handler command is meant to report the exception +in an application-specific fashion. The handler command +receives two arguments, the result of the interp, and the +return options of the interp at the time the error occurred. +If the application registers no handler command, the default +handler command will attempt to call \fBbgerror\fR to report +the error. If an error condition arises while invoking the +handler command, then \fBTcl_BackgroundException\fR reports the +error itself by printing a message on the standard error file. +.PP +\fBTcl_BackgroundException\fR does not invoke the handler command immediately +because this could potentially interfere with scripts that are in process +at the time the error occurred. +Instead, it invokes the handler command later as an idle callback. +.PP +It is possible for many background exceptions to accumulate before +the handler command is invoked. When this happens, each of the exceptions +is processed in order. However, if the handler command returns a +break exception, then all remaining error reports for the +interpreter are skipped. +.PP +The \fBTcl_BackgroundError\fR routine is an older and simpler interface +useful when the exception code reported is \fBTCL_ERROR\fR. It is +equivalent to: +.PP +.CS +Tcl_BackgroundException(interp, TCL_ERROR); +.CE + +.SH KEYWORDS +background, bgerror, error, interp |