backgderr(3Tk)

NAME
     Tk_BackgroundError - report Tcl error that occurred in background
     processing

SYNOPSIS
     #include <tk.h>

     Tk_BackgroundError(interp)

ARGUMENTS
     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 a Tcl command in response to
     a button press or menu entry invocation.  When such an error occurs, the
     error condition is reported to Tk 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 Tk_BackgroundError with
     an interp argument identifying the interpreter in which the error
     occurred.  Tk_BackgroundError attempts to invoke the tkerror Tcl command
     to report the error in an application-specific fashion.  If no tkerror
     command exists, or if it returns with an error condition, then
     Tk_BackgroundError reports the error itself by printing a message on the
     standard error file.

     Tk_BackgroundError does not invoke tkerror immediately (in some cases    |
     this could interfere with scripts that are in process at the time the    |
     error occurred).  Instead, it invokes tkerror later as an idle callback. |
     Tk_BackgroundError saves the values of the errorInfo and errorCode       |
     variables and restores these values just before invoking tkerror.        |

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


KEYWORDS
     background, error, tkerror