Restrictions on Data Entry Error Handlers
A data entry error handler is subject to the following restrictions that are imposed on the handler and on any procedures or methods it calls:
• Handlers cannot invoke a frame; the callframe, gotoframe, and openframe statements are all illegal.
• Handlers cannot wait for user events or database events, but they can issue database queries and do file I/O.
• The OpenROAD Debugger does not stop at breakpoints or for any other condition during the execution of the handler.
Statements that usually cause display of a pop-up frame (when executed outside a data entry error handler), such as the message statement and the ConfirmPopup method, are written to the trace window and the w4gl.log file.
Except for message statements, such statements cause the entire OpenROAD process to wait for a response, even if there are other threads that could run.
A handler can be in a thread different from that of the frame that encountered the error, even if the handler is a local procedure.
Note: The error handlers described in this section do not apply to database errors. For more information about handling database errors, see
Working with a Database (see
Working with a Database).