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Room Description Layout Issues

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Posted by Nick Gammon Australia (23,158 posts) Bio Forum Administrator

Date Reply #15 on Wed 07 Feb 2007 09:32 PM (UTC)

Message

As far as I can see, some MUDs (SMAUG springs to mind) tend to send a combination of \r or \r\n to mark end of lines. For example, internal code tends to use \r\n (for some reason), however routines that "dump" a file to the client (eg. a help file) tend to send it "as is" which will generally be with only \n at the end of lines, if the file was edited under Unix.

This means that a standard telnet client will "sort of" work, which isn't particularly helpful.

What MUSHclient does, and I imagine others do too, is do this:

Discard \r totally - to avoid the double-spacing issue
Start a new line at \n

However MXP tags can modify that behaviour too, making lines wrap around, even after a \n (like HTML does).

This behaviour can sometimes lead to problems, such as MUDs that do things like a "milestone count" by sending something like:



\r 10% \r 20% \r 30% ... and so on

In this case, the \r is supposed to return the cursor to the start of the line, to "wipe out" the previous percentage.

There is an option in MUSHclient for \r to "clear the line" which effectively should make that sort of stuff work. I know it isn't perfect, as \r isn't supposed to actually clear the line, however for the sort of situation described above, that is acceptable.

- Nick Gammon

www.gammon.com.au, www.mushclient.com

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Posted by

Meerclar USA (733 posts) Bio

Date

Reply #16 on Wed 07 Feb 2007 09:40 PM (UTC)

Message

Ok, so I kinda had the client interpretation backwards, but based on this excerpt from the telnet protocol whitepaper (http://www.faqs.org/rfcs/rfc854.html)

Quote:

The sequence "CR LF", as defined, will cause the NVT to be
positioned at the left margin of the next print line (as would,
for example, the sequence "LF CR"). However, many systems and
terminals do not treat CR and LF independently, and will have to
go to some effort to simulate their effect. (For example, some
terminals do not have a CR independent of the LF, but on such
terminals it may be possible to simulate a CR by backspacing.)
Therefore, the sequence "CR LF" must be treated as a single "new
line" character and used whenever their combined action is
intended; the sequence "CR NUL" must be used where a carriage
return alone is actually desired; and the CR character must be
avoided in other contexts. This rule gives assurance to systems
which must decide whether to perform a "new line" function or a
multiple-backspace that the TELNET stream contains a character
following a CR that will allow a rational decision.

The actual clients are following the standard as written.

Meerclar - Lord of Cats
Coder, Builder, and Tormenter of Mortals
Stormbringer: Rebirth
storm-bringer.org:4500
www.storm-bringer.org

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