[Info-vax] escape sequences, cursor positioning

[Johnny Billquist]

sol gongola skrev:
> Jan-Erik Söderholm wrote:
>> SMS wrote:
>>> Jan-Erik Söderholm wrote:
>>>> SMS wrote:
>>>>> JF Mezei wrote:
>>>>>
>>>>>> DECTERM doesn't do display control characters. [...]
>>>>>    I believe that mine do.  I've just been using
>>>>> EDIT /TPU to look at a log file from  a
>>>>> "SET HOST 0 /LOG" command, and I see a
>>>>> whole collection of cute little [C/R] and [N/L]
>>>>> characters on my screen.
>>>> Aren't they displayed by TPU, not by the DECTerm ?
>>>> That is, when they are sent to DECTerm, they are not
>>>> control characters but the actual characters "C", "/",
>>>> "R" and "N", "/", "L".
>>>    No, I mean single-cell characters which look roughly like:
>>>
>>>       +--+      +--+
>>>       |C |      |N |
>>>       | R|      | L|
>>>       +--+      +--+
>>>
>>>    As for who's displaying them, well, TPU/EVE is telling the DECterm
>>> what to do, and the DECterm is doing it.  According to my handy "VT
>>> 220
>>> Programmer Pocket Guide", these are in the DEC Special Graphics
>>> character set
>> Right then, then they are still not "controll characters".
>> It's still something TPU is sending to be displayed, not
>> true CR and LF characters...
>>
>> What JF was talking about was when the term-emulator
>> displays "C/R" (or similar text) instead of actualy
>> performing the "carriage return" or "line feed" operation.
>>
>> Jan-Erik.
>>
>>
>>  (with all the L- and T-shapes in different orientations,
>>> and the horizontal lines at five different heights, and the rest of
>>> the
>>> fun stuff).  Anyone doing serious VT100 graphics needs to know about
>>> these (and the SO (%x0E) and SI (%x0F) characters to switch back and
>>> forth between G0 and G1).  (It's all in the book, and I haven't really
>>> cared since about 1985.  And thanks for reminding me.)
>>>
>>> --------------------------------------------------------
>>>
>>>    Steven M. Schweda               sms at antinode-info
>>>    382 South Warwick Street        (+1) 651-699-9818
>>>    Saint Paul  MN  55105-2547
> 
> The cr lf characters are displayed when they are outside the standard crlf sequence.

No. The C/R and L/F characters are displayed when you select the DEC technical 
character set (and that involves more than just using the SI and SO codes), or 
when you set the terminal to display control characters. In the latter case, CR 
and LF are displayed, but they are also among the few characters that the 
terminal also still interprets and executes.

Sending a CR without an LF or vice verse is definitely not uncommon or strange, 
and it would be very weird and bad if they were displayed just because they 
didn't come in pairs.

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
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