Teletext separated mosaic graphics

[William_J_G Overington]

I am now thinking that the best solution for encoding the teletext 
control characters using just already existing Unicode characters is to 
use the Escape format listed in the PDF document linked from the post by 
Harriet Riddle.

https://www.itscj.ipsj.or.jp/iso-ir/056.pdf

https://corp.unicode.org/pipermail/unicode/2020-October/009048.html

This appears to be what is used in the export format named viewdata from 
the editor that Kent Karlsson mentioned.

https://zxnet.co.uk/teletext/editor

https://corp.unicode.org/pipermail/unicode/2020-October/009071.html

If one then uses a specially made OpenType font, one can arrange for 
each such two character escape sequence to be displayed as one of the 
glyph designs that I mentioned in the following post, by using the 
OpenType liga facility..

https://corp.unicode.org/pipermail/unicode/2020-October/009047.html

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

This morning I tried making a test font with a visible glyph for the 
Escape character and a liga glyph substitution for Escape followed by 
capital A.

I made the font using the High-Logic FontCreator program and tested it 
in the Serif Affinity Publisher program, producing a PDF document.

I was hoping to be able to paste a copy of the substituted glyph copied 
from the PDF to WordPad and recover the underlying two character 
sequence. However I could only seem to get the capital A back. Maybe I 
did not get the technique quite right and so it might perhaps be 
possible to get the underlying sequence back from a PDF, but that 
requires further investigation.

William Overington

Tuesday 13 October 2020