A last missing link for interoperable representation

wjgo_10009@btinternet.com via Unicode unicode at unicode.org
Tue Jan 15 05:32:34 CST 2019

Martin J. Dürst wrote:

> So rich text technology is already way ahead when it comes to styled 
> text. Do we want to encode background-color variant selectors in 
> Unicode? If yes, how many?


You would only need one.

Background colour was a feature of teletext in the United Kingdom from 
1976. It was very effective in its application.

In teletext, there were seven choices of foreground colour (red, green, 
yellow, blue, magenta, cyan, white), the default background was black.

The New Background control character caused the background colour to 
become the same as the current foreground colour in which text was being 
displayed. One could then change the foreground colour.

There was also a Black Background control code. This was necessary 
because neither text nor graphics could be black in teletext.

In teletext those control codes were stateful and applied until a change 
or to the end of the line of text, whichever came first.

So, given that Unicode is starting to encode colour choices for emoji 
and black is in the set of colours - and that might possibly extend to 
choosing colour for text - if Unicode were to encode CHANGE BACKGROUND 
COLOUR then the background colour could become the current foreground 
colour, even if that chosen foreground colour had just been selected and 
not actually used to colour text.

The implementation in Unicode need not be stateful.

> [Hint: The last two questions are rhetorical.]

Maybe that was the intention, but the questions were asked and the 
concept is an interesting possibility for implementation.

William Overington

Tuesday 15 January 2019

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