Handles twain messages. This is called only within your message loop if you are not using REXX GUI's default twain processing. Is it intended to be used only in conjunction with other software that requires special message processing (as Twain does). Normally, you will not need this.
Synopsis
result = TwainDoMsg(msgHandle)
Args
msgHandle is the handle to some message received by your GUI window.
Returns
An empty string if not a twain event. The script's Message handler may want to do other message processing if it has other events to check.
Returns "NO" if an unknown twain event.
Returns "YES" if a known twain event (in which case GuiSignal = "TWAIN" and GuiSignal is "XFER" if a transfer operation is complete or "CLOSED" if the user disabled/closed the data source). In this case, the script's Message handler should return "NO".
Returns some numeric value(s) if an error. The script's message handler should RAISE whatever condition it wants raised, or return some reformatted error message.