Re: [css-text] Control characters

On 20/3/14 04:57, Robert O'Callahan wrote:
> On Thu, Mar 20, 2014 at 11:00 AM, James Clark <
> <>> 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
> 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.

For some further discussion, see comments (arguing both for and against 
such a change) in relevant mozilla bugs, such as:


Received on Thursday, 20 March 2014 16:00:39 UTC