Tcl_BackgroundError (3)
report Tcl error that occurred in background processing
SYNOPSIS
#include <tcl.h>
Tcl_BackgroundError(interp)
ARGUMENTS
Tcl_Interp *interp
Tcl_Interp *interp in
Interpreter in which the error occurred.
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,
interp->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
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