A couple of your questions are addressed by: http://www.unicode.org/faq/unsup_char.html
In particular: Q: Which characters should be displayed with a missing glyph, if not supported? A: All characters other than whitespace and default-ignorable characters. James On Mon, Jun 30, 2014 at 1:44 AM, Koji Ishii <[email protected]> wrote: > Hello Unicoders, > > I’m a co-editor of CSS Text Level 3[1], and I would appreciate your > support in defining rendering behavior in CSS. > > The spec currently has the following text[2]: > > > 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. (As required by [UNICODE], unsupported Default_ignorable > characters must also be ignored for rendering.) > > and there’s a feedback saying that CSS should display visible glyphs for > these control characters. Since all major browsers do not display them > today, this is a breaking-change and the CSS WG needs to discuss on this > feedback. But the WG would appreciate to understand what Unicode recommends. > > I found the following text in Unicode 6.3, p. 185, "5.21 Ignoring > Characters in Processing”[3]: > > > Surrogate code points, private-use characters, and control characters > are not given the Default_Ignorable_Code_Point property. To avoid security > problems, such characters or code points, when not interpreted and not > displayable by normal rendering, should be displayed in fallback rendering > with a fallback glyph > > By looking at this, my questions are as follows: > > 1. Should control characters that browsers do not interpret be displayed > in fallback rendering? > 2. Should private-use characters (U+E000-F8FF, 0F0000-0FFFFD, > 100000-10FFFD) without glyphs be displayed in fallback rendering? > > These two questions are probably yes from what I understand the text > quoted above, but things get harder the more I think: > > 3. When the above text says “surrogate code points”, does that mean > everything outside BMP? It reads so to me, but I’m surprised that > characters in BMP and outside BMP have such differences, so I’m doubting my > English skill. > 4. Should every code point that are not given the > Default_Ignorable_Code_Point property and that without interpretations nor > glyphs displayed in fallback rendering? I could not find such statement in > Unicode spec, but there are some people who believe so. > 5. Is there anything else Unicode recommends to display in fallback > rendering, or not to display? This must be RTFM, but pointing out where to > read would be appreciated. > > Thank you for your support in advance. > > [1] http://dev.w3.org/csswg/css-text/ > [2] http://dev.w3.org/csswg/css-text/#white-space-processing > [3] http://www.unicode.org/versions/Unicode6.3.0/ch05.pdf > > /koji > > > _______________________________________________ > Unicode mailing list > [email protected] > http://unicode.org/mailman/listinfo/unicode >
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