This character is a Nonspacing Mark and inherits its script property from the preceding character. It is also used in the scripts Caucasian Albanian, Cherokee, Coptic, Cyrillic, Gothic, Greek, Latin, Osage, Syriac, Tifinagh, Todrhi. The character is also known as long.
The glyph is not a composition. Its width in East Asian texts is determined by its context. It can be displayed wide or narrow. In bidirectional text it acts as Nonspacing Mark. When changing direction it is not mirrored. U+0304 prohibits a line break before it. The glyph can be confused with 10 other glyphs.
The Wikipedia has the following information about this codepoint:
A macron ( MAK-ron, MAY-) is a diacritical mark: it is a straight bar ¯ placed above a letter, usually a vowel. Its name derives from Ancient Greek μακρόν (makrón) 'long' because it was originally used to mark long or heavy syllables in Greco-Roman metrics. It now more often marks a long vowel. In the International Phonetic Alphabet, the macron is used to indicate a mid-tone; the sign for a long vowel is instead a modified triangular colon ⟨ː⟩.
The opposite is the breve ⟨˘⟩, which marks a short or light syllable or a short vowel.
Representations
System
Representation (click value to copy)
Nº
772
UTF-8
CC 84
UTF-16
03 04
UTF-32
00 00 03 04
URL-Quoted
%CC%84
HTML hex reference
̄
Wrong windows-1252 Mojibake
◌̄
alias
long
Encoding: EUC_JIS_2004 (hex bytes)
AB DB
Encoding: EUC_JISX0213 (hex bytes)
AB DB
Encoding: GB18030 (hex bytes)
81 30 BD 30
Encoding: ISO2022_JP_2004 (hex bytes)
1B 24 28 51 2B 5B 1B 28 42
Encoding: ISO2022_JP_3 (hex bytes)
1B 24 28 4F 2B 5B 1B 28 42
Encoding: SHIFT_JIS_2004 (hex bytes)
86 7A
Encoding: SHIFT_JISX0213 (hex bytes)
86 7A
LATEX
\=
AGL: Latin-4
uni0304
AGL: Latin-5
uni0304
Adobe Glyph List
macroncmb
RFC 5137
\u'0304'
Bash and Zsh inside echo -e
\u0304
C and C++
\u0304
C#
\u0304
CSS
\000304
Excel
=UNICHAR(772)
Go
\u0304
JavaScript
\u0304
Modern JavaScript since ES6
\u{304}
JSON
\u0304
Java
\u0304
Lua
\u{304}
Matlab
char(772)
Perl
"\x{304}"
PHP
\u{304}
PostgreSQL
U&'\0304'
PowerShell
`u{304}
Python
\u0304
Ruby
\u{304}
Rust
\u{304}
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