nadji@uscvax.UUCP (Behzad Nadji) (12/28/85)
What is a terminal emulator supposed to do when it receives an
invalid escape sequence. For example, what should a VT52 emulator
do when it receives an <Esc>M or <Esc>X ?
1- Ignore the sequence.
2- Write it to screen as it is.
3- Ignore the sequence, but indicate an error (by a beep or by writing a
block (?) character to screen).
4- Write it to screen as it is, but indicate an error as above.
5- others?
Choices 3 and 4 sound awful; 1 is ok but may cause problems if the actual
text being received contains the <Esc> character. My choice has been 2 but
I was wondering if anyone knows what the standard is.
ARPA: nadji%usc-cse@csnet-relay.arpa
CSNET: nadji@usc-cse.csnetac4@pucc-j (Tom Putnam) (01/03/86)
In article <171@uscvax.UUCP> nadji@uscvax.UUCP (Behzad Nadji) writes: >What is a terminal emulator supposed to do when it receives an >invalid escape sequence? I wrote a terminal emulator and had to deal with this question. I think there are two answers: 1) Ignore the sequence. The "typical" user doesn't care unless it is a sequence that invokes a function that he needs. If you don't support that function for some reason (incomplete emulation), then your user isn't going to be any happier if you tell him about it. 2) Provide a debug mode where you ignore the sequence but tell the user about it. My terminal emulator uses the 25th line of the display to flash such messages for about 3 seconds. I have found it is quite useful in debugging not only my emulator but also debugging the various terminal packages and systems I use it with. I use the 25th line as a temporary status line (window?). You can save it and restore it if necessary to provide complete emulation capabilities. Be sure to include the full text of the escape sequence in the message - easy enough to do since you don't have to deal with non-printing control characters. -- Tom Putnam, Manager of User Services Purdue University Computing Center ARPANET: ac4@asc.Purdue.EDU or ac4@purdue-asc.ARPA BITNET: PUTNAMT@PURCCVM CSNET: ac4@purdue-asc-tn USENET: ac4@pucc-j.UUCP USMAIL: Mathematical Sciences Bldg. West Lafayette, IN 47907 PHONE: 317/494-1787