Teletext separated mosaic graphics

[William_J_G Overington]

The 1976 Teletext Specification has three meanings for sixty-four of the 
character code points - lowercase letters and a few others, contiguous 
graphics, separated graphics.

The Unicode Standard at present has the "lowercase letters and a few 
others" encoded and the "contiguous graphics" encoded separately, 
although, alas, all sixty-four contiguous graphic characters are not 
encoded as one block. My opinion is that that one-to-one directly mapped 
approach would have been preferable, but the situation is as it is.

The twenty-seven teletext control characters have not been encoded at 
this time.

I opine that these twenty-seven codes could be encoded within a block of 
thirty-two code points as characters that display as visual glyphs in 
most circumstances, yet are control codes in teletext apps.

For example, Alphanumerics Green would have a visible glyph of an A 
above a G on a pale.

That way, teletext pages from long ago and new designs could be recorded 
elegantly and conserved as the control codes in the teletext page would 
not conflict with the usual control codes of computing.

If those twenty-seven teletext control characters were encoded 
separately, would that help in developing your app, or are you using a 
different approach?

William Overington

Thursday 1 October 2020

http://www.users.globalnet.co.uk/~ngo/


------ Original Message ------
From: "Rob H via Unicode" <unicode at unicode.org>
To: unicode at unicode.org
Sent: Thursday, 2020 Oct 1 At 13:46
Subject: Teletext separated mosaic graphics

Hi,

I've started to develop a teletext app and plan to use the recently 
added graphic mosaic characters in the legacy computing block (the 
sextets).  I see that Unicode includes the contiguous mosaics characters 
and not the separated form of those characters.  I'm wondering if that 
was intentional?  On one hand, that matches the teletext spec, which has 
one set of byte codes for the graphics, and uses control codes to switch 
between contiguous or separated.  On the other hand it means I'll need 
to use styling tricks or a different font or glyph variations to 
recreate the separated graphics.  It also means a simple text-only file 
of just the characters won't recreate a screen as the control codes to 
switch between contiguous/separated won't work.


A font I've found which maps these characters uses the new codepoints 
for the contiguous graphics and  a private codepoints for separated, 
which seems awkward to me.


If having just the contiguous graphics was intentional, that's fine, but 
I just wanted to check.


Regards,
Rob.


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