Coloured Punctuation and Annotation

Peter Constable via Unicode unicode at
Mon Apr 10 17:08:14 CDT 2017


Michael's scenario doesn't require a special palette index value such as you propose since (i) he could implement a font with alternate palettes to provide different colouring options of his choosing, and (ii) an app can always expose customization options to allow the user to customize any of the palette entries that are being used, even on a character-by-character basis if the app really wanted to.

Moreover, defining palette index 0xFFFE with a special meaning would be a breaking change that could negatively impact existing implementations. Also, it would create a potential ambiguity about what colour to use: whereas text drawing operations _always_ have a foreground colour specified, there is no convention for specifying a "first decoration colour". 

For these reasons, this is not going to happen.


-----Original Message-----
From: Unicode [mailto:unicode-bounces at] On Behalf Of William_J_G Overington
Sent: Thursday, April 6, 2017 11:40 AM
To: everson at; richard.wordingham at; unicode at
Subject: Re: Coloured Punctuation and Annotation

Michael Everson wrote:

> No. Here is an example of a font available in two variants. In one variant, all those grey swirls are fused to the letters, and it can all be printed in black or one colour ink. 


> There is also a second set of fonts included which separates the swirls from the letters, and those can be used in typesetting to get the two-colour effect you see here. That can’t really be done using standard encoding. You’d probably see IIVVOORRYY in the backing store for that word, with every other letter being set in the letter font and the swirl font. 

Richard Wordingham mentioned the following.

> The third glyph would use 'index' 0xFFFF to specify that it be displayed in the foreground colour.

If the OpenType specification were augmented so that 'index' 0xFFFE were to specify that the appropriate part of the glyph be displayed in the "first decoration colour", a colour specified in the application program and not in the font; and an application program were augmented so that an end user were able to choose first decoration colour as well as choosing foreground colour, then would that produce the result for which Michael is looking?

William Overington

Thursday 6 April 2017

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