make a list of invisible characters to support html 5121 discussion

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Opened by @aphillips via IRC channel #i18n on irc.w3.org

Due: 2024-02-22 (Thursday 22 February)

[r12a]

Priority items

For me, of those that are missing, these are the highest priority. I suggest possible named entities, derived from the standard Unicode abbreviations.

• U+061C ARABIC LETTER MARK. &alm;
• U+180E MONGOLIAN VOWEL SEPARATOR &mvs;
• U+202D LEFT-TO-RIGHT OVERRIDE &lro;
• U+202E RIGHT-TO-LEFT OVERRIDE &rlo;
• U+2066 LEFT-TO-RIGHT ISOLATE &lri;
• U+2067 RIGHT-TO-LEFT ISOLATE. &rli;
• U+2068 FIRST STRONG ISOLATE. &fsi;
• U+2069 POP DIRECTIONAL ISOLATE &pdi;
• U+202F NARROW NO-BREAK SPACE &nnbsp;
• U+034F COMBINING GRAPHEME JOINER &cgj;
• U+180B MONGOLIAN FREE VARIATION SELECTOR ONE &fvs1;
• U+180C MONGOLIAN FREE VARIATION SELECTOR TWO &fvs2;
• U+180D MONGOLIAN FREE VARIATION SELECTOR THREE &fvs3;
• U+180F MONGOLIAN FREE VARIATION SELECTOR FOUR &fvs4;

I'd also like to have &zwsp; in addition to ​for U+200B

Full list

It took a while to figure out how to come up with a reasonable list. The following is from From https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5B%3Adi%3A%5D%5B%3Awhite_space%3A%5D-%5B%3ACn%3A%5D&g=&i=
but with some items manually excised because i felt they were not necessary. I marked in bold the ones for which we already have named entities. Ones i'm not sure about are in italics.

Latin 1 Supplement — Latin-1 punctuation and symbols

• U+00A0 NO-BREAK SPACE  
• U+00AD SOFT HYPHEN ­

Combining Diacritical Marks — Grapheme joiner

• U+034F COMBINING GRAPHEME JOINER

Arabic — Format character

• U+061C ARABIC LETTER MARK

Hangul Jamo — Old initial consonants

• U+115F HANGUL CHOSEONG FILLER

Hangul Jamo — Medial vowels

• U+1160 HANGUL JUNGSEONG FILLER

Ogham — Space

• U+1680 OGHAM SPACE MARK

Mongolian — Format controls

• U+180B MONGOLIAN FREE VARIATION SELECTOR ONE
• U+180C MONGOLIAN FREE VARIATION SELECTOR TWO
• U+180D MONGOLIAN FREE VARIATION SELECTOR THREE
• U+180E MONGOLIAN VOWEL SEPARATOR
• U+180F MONGOLIAN FREE VARIATION SELECTOR FOUR

General Punctuation — Spaces

• U+2000 EN QUAD
• U+2001 EM QUAD
• U+2002 EN SPACE  
• U+2003 EM SPACE  
• U+2004 THREE-PER-EM SPACE  
• U+2005 FOUR-PER-EM SPACE  
• U+2006 SIX-PER-EM SPACE
• U+2007 FIGURE SPACE  
• U+2008 PUNCTUATION SPACE  
• U+2009 THIN SPACE   AND  
• U+200A HAIR SPACE   AND   AND part of    (U+0205F U+200A)

General Punctuation — Format character

• U+200B ZERO WIDTH SPACE ​ AND ​ AND ​ AND ​ AND ​
• U+200C ZERO WIDTH NON-JOINER ‌
• U+200D ZERO WIDTH JOINER ‍
• U+200E LEFT-TO-RIGHT MARK ‎
• U+200F RIGHT-TO-LEFT MARK ‏
• U+202A LEFT-TO-RIGHT EMBEDDING
• U+202B RIGHT-TO-LEFT EMBEDDING
• U+202C POP DIRECTIONAL FORMATTING
• U+202D LEFT-TO-RIGHT OVERRIDE
• U+202E RIGHT-TO-LEFT OVERRIDE
• U+2060 WORD JOINER ⁠
• U+2066 LEFT-TO-RIGHT ISOLATE
• U+2067 RIGHT-TO-LEFT ISOLATE
• U+2068 FIRST STRONG ISOLATE
• U+2069 POP DIRECTIONAL ISOLATE

General Punctuation — Separators

• U+2028 LINE SEPARATOR
• U+2029 PARAGRAPH SEPARATOR

General Punctuation — Space

• U+202F NARROW NO-BREAK SPACE
• U+205F MEDIUM MATHEMATICAL SPACE   AND part of    (U+205F U+200A)

General Punctuation — Invisible operators

• U+2061 FUNCTION APPLICATION ⁡ AND ⁡
• U+2062 INVISIBLE TIMES ⁢ AND ⁢
• U+2063 INVISIBLE SEPARATOR ⁣ AND ⁣
• U+2064 INVISIBLE PLUS
• U+206D ACTIVATE ARABIC FORM SHAPING

CJK Symbols And Punctuation — CJK symbols and punctuation

• U+3000 IDEOGRAPHIC SPACE

Hangul Compatibility Jamo — Special character

• U+3164 HANGUL FILLER

Halfwidth And Fullwidth Forms — Halfwidth Hangul variants

• U+FFA0 HALFWIDTH HANGUL FILLER

Shorthand Format Controls — Shorthand format controls

• U+1BCA0 SHORTHAND FORMAT LETTER OVERLAP
• U+1BCA1 SHORTHAND FORMAT CONTINUING OVERLAP
• U+1BCA2 SHORTHAND FORMAT DOWN STEP
• U+1BCA3 SHORTHAND FORMAT UP STEP

Musical Symbols — Beams and slurs

• U+1D173 MUSICAL SYMBOL BEGIN BEAM
• U+1D174 MUSICAL SYMBOL END BEAM
• U+1D175 MUSICAL SYMBOL BEGIN TIE
• U+1D176 MUSICAL SYMBOL END TIE
• U+1D177 MUSICAL SYMBOL BEGIN SLUR
• U+1D178 MUSICAL SYMBOL END SLUR
• U+1D179 MUSICAL SYMBOL BEGIN PHRASE
• U+1D17A MUSICAL SYMBOL END PHRASE

Emoji Variation Selectors - turns on and off colour

• U+FE0E: VARIATION SELECTOR-15
• U+FE0F: VARIATION SELECTOR-16

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Closed by @aphillips via IRC channel #i18n on irc.w3.org