[Info-vax] escape sequences, cursor positioning

[Johnny Billquist]

JF Mezei skrev:
> David J Dachtera wrote:
> Now, looking at the original screen display for something at line 8
> column 34:
> 
> •[8;32H•[;1;7m  •[8;34H  0.00•[9;2H etc
> 
> So, it moves to column 32, sets attribute to bold (1) and reverse video
> (8) writes 2 spaces, then moves to 8;34, and writes the field contents
> (2 spaces followed by 0.00 and then moves on to the next field.
> 
> So it appears that during entry, you can rewrite the contents at that
> location of the screen and the video attributes are preserved.

Bzzt. No.
Apart from the fact that the display driver seems a bit stupid (why do a cursor 
movement to exactly the place you're already at?), what you need to remember is 
that when you set attributes, they remain active until changed. Moving the 
cursor around won't change that.
So the above sequence will move to (8,32), turn off all attributes, turn on 
bold(1) and reverse(7), write two spaces with these attributes, move the cursor 
to (8,34) (where it is already at after the previous two spaces), write "  0.00" 
still with the same attributes previously set, and then move on to (9,2), and so 
on...

And why I say turn off all attibutes - please note the sequence. It is:
<CSI>;1;7m

The initial ; means that you have a (silent) zero first of all. More explicitly, 
it would be written:
<CSI>0;1;7m

(And I use <CSI> here, since that's the correct name of the sequence. And it can 
be sent either as "<ESC>[" or as "<CSI>". The latter is an 8-bit code with the 
octal value of 233. The latter will only work if your terminal actually 
understands 8-bit control codes.)

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
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