Tcl_BackgroundError(3)					      Tcl Library Procedures					    Tcl_BackgroundError(3)

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NAME

       Tcl_BackgroundError - report Tcl error that occurred in background processing

SYNOPSIS

       #include <tcl.h>

       Tcl_BackgroundError(interp)

ARGUMENTS

       Tcl_Interp   *interp   (in)	Interpreter in which the error occurred.
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DESCRIPTION

       This procedure is typically invoked when a Tcl error occurs during ``background processing'' such as executing an event handler.  When such
       an error occurs, the error 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  error  to the user.  In these cases the code calls Tcl_BackgroundError with an interp argument identifying the
       interpreter in which the error occurred.  At the time Tcl_BackgroundError is invoked, the interpreter's result is expected  to  contain	an
       error  message.	 Tcl_BackgroundError  will  invoke  the bgerror Tcl command to report the error in an application-specific fashion.  If no
       bgerror command exists, or if it returns with an error condition, then Tcl_BackgroundError reports the error itself by printing	a  message
       on the standard error file.

       Tcl_BackgroundError  does  not  invoke bgerror immediately because this could potentially interfere with scripts that are in process at the
       time the error occurred.  Instead, it invokes bgerror later as an idle callback.  Tcl_BackgroundError saves the values of the errorInfo and
       errorCode variables and restores these values just before invoking bgerror.

       It  is  possible for many background errors to accumulate before bgerror is invoked.  When this happens, each of the errors is processed in
       order.  However, if bgerror returns a break exception, then all remaining error reports for the interpreter are skipped.

KEYWORDS

       background, bgerror, error

Tcl									7.5						    Tcl_BackgroundError(3)