Teletext separated mosaic graphics

William_J_G Overington wjgo_10009 at
Mon Oct 5 07:25:56 CDT 2020

Doug Ewell wrote:

> UTC has confirmed it will not add more control characters for backward 
> compatibility purposes like this. (I don't think there is a promise 
> not to encode more completely novel control characters, such as for 
> hieroglyphics, but that is not the question here.)

Well, at one stage the Unicode Technical Committee decided not to encode 
emoji then later changed its mind, so changes can be made if later 
consideration is assessed as justifying that change. That does not mean 
that the Unicode Technical Committee will necessarily change its mind, 
it just means that it could change its mind if it so chooses.

> We all know there is no such thing in Unicode as a "hybrid" character 
> that is sometimes a control character and sometimes a graphic 
> character in normal use. We know that Unicode has defined fixed 
> meanings for a subset of the C0 control characters, including CR and 
> LF. But a teletext application for a modern computer is not "normal 
> use." It is reasonable for a non-standard application like this to 
> interpret characters from U+0000 to U+001F as the corresponding ISO 
> 646 characters would be in teletext. It is, frankly, the only choice.

There is a choice. If the teletext control codes are encoded as if 
ordinary displayable characters with a note saying that they may, but 
need not, be interpreted as teletext control characters then it would be 
possible to have teletext-aware web browsers and teletext-aware PDF 
readers and so on where a teletext page could be included within a 
document using a plain text representation.

William Overington

Monday 5 October 2020

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