Re: [css-text] Control characters

On Thu, Mar 20, 2014 at 11:00 AM, James Clark <jjc@jclark.com> wrote:

> CSS Text says:
>
> Control characters (Unicode class Cc) other than tab (U+0009), line feed
>> (U+000A), and carriage return (U+000D) are ignored for the purpose of
>> rendering.
>
>
> (This is a change from CSS 2.1, which says they are rendered as usual.) I
> was wondering what the thinking is here.  This requirement conflicts with
> Unicode (see http://www.unicode.org/faq/unsup_char.html) in a couple of
> ways:
>
> 1. In addition to 0x9, 0xA and 0xD, Unicode gives characters 0xB (VT), 0xC
> (FF) and 0x85 (NEL) the White_Space property.  Characters with the
> White_Space property are supposed to be rendered as a visible but blank
> space. (Of these, HTML includes only 0xC as a space character.)
>
> 2. Other control characters are supposed to be rendered normally (ie
> displayed with a missing glyph if not available in the font).
>

We had a discussion about this a while back within Mozilla; some people
like the idea of displaying control characters so that such 'soft errors'
in pages can be more easily detected and fixed.

We ended up defining an internal CSS property
'-moz-control-character-visibility:visible|hidden', with initial value
hidden, but we set it to visible for devtools, plain text files, the
contents of text inputs, view-source, etc. We could easily standardize that
if other people are interested.

Rob
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