What is the unicode variation selector

问题:

I was wondering. What is the unicode Variation Selectors U-FE00 to U-FE0F used for.

Example:

回答1:

The Unicode standard talks about this. Here's a bit of the relevant section from 3.2.0, annex 28 (I'm sure there are more recent versions around; this is the first I found):

Unicode characters can be represented by a wide variety of glyphs, as discussed in Chapter 2, General Structure in The Unicode Standard, Version 3.0. Occasionally the need arises in text processing to restrict or change the set of glyphs that are to be used to represent a character. Normally such changes are indicated by choice of font or style in rich-text documents. In special circumstances, such a variation from the normal range of appearance needs to be expressed side-by-side in the same document in plain-text contexts, where it is impossible or inconvenient to exchange formatted text. For example, in languages employing the Mongolian script, sometimes a specific variant range of glyphs is needed for a specific textual purpose for which the range of “generic” glyphs is considered inappropriate. The variation selectors are used when characters have essentially the same semantic.

Variation selectors provide a mechanism for specifying a restriction on the set of glyphs that are used to represent a particular character. They also provide a mechanism for specifying variants, such as for CJK Ideographs and Mongolian, that have essentially the same semantic but have substantially different ranges of glyphs. A variation sequence, which always consists of a base character followed by the variation selector, may be specified as part of the Unicode Standard. That sequence is referred to as a variant of the base character. The variation selector affects only the appearance of the base character,* and only in the variation sequences defined in this Standard. The variation selector is not used as a general code extension mechanism.

(It goes on...)

You may also be interested in the Standardized Variants (this time from 6.0.0).

回答2:

Your guess is as good as mine.. but according to this source...

has got it...

Emoji Character Encoding Data Hints: 1 In iOS 5 / OSX 10.7, the underlying code that the Apple OS generates for this emoji was changed.2 The code generated for this emoji was changed slightly in iOS 7 / OSX 10.9 (a variation selector was added) to make it easier for this emoji to be identified and shown in OSX and iOS. We don't mind Apple, thank you! We just love our emojis!

Their chart goes on to note that this "new", post-10.9 version

has a UTF-8 Character Count of 2 vs the previous 1... if that helps.

回答3:

The Variation Selectors range was introduced with version 3.2 of the Unicode Standard, and is located in Plane 0, the Basic Multilingual Plane. Further selectors can be found in the Variation Selectors Supplement range.

Most Unicode characters can be represented by a wide variety of glyphs, and in rich text a particular glyph can be indicated by choosing a particular font or style. This mechanism is not available in plain text, and so variation selectors have been introduced as a way of indicating that the glyphs applicable to a particular character should be changed or restricted. The base character is followed by the variation selector, the combination being called a variation sequence. This is not intended to be general-purpose mechanism, and the only permitted variation sequences are those defined in the Standardized Variants file, which forms part of the Unicode Character Database.

From http://www.alanwood.net/unicode/variation_selectors.html

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