Try looking up han-unification and its justification and you'll see the exact opposite approach to encoding characters into unicode.
For CJK characters, they unified all semantically similar han-characters, even when they have visual forms that are quite different between Japanese, Chinese and Korean.
If you want to write Japanese and Chinese in the same document, you need to mark up the section to tell the system that renders it, to render different visual forms for similar codepoints depending on whether they are used in Japanese or Chinese.
> For CJK characters, they unified all semantically similar han-characters, even when they have visual forms that are quite different between Japanese, Chinese and Korean.
This isn't true. 青 and 靑 are the same character written differently; they have their own codepoints. Ditto for a huge number of simplified Chinese characters; 语 is mainland Chinese and 語 is the same character in Japanese.
It is true for lots of characters (so I guess I was being a little hyperbolic when I said "all"), and you cannot rely on choosing the correct code points in order to have a text display Japanese or Chinese. You need to tell your rendering program (often through choice of font) if things are to be rendered with Japanese or Chinese forms.
I wouldn't know how to show you examples here, as 直 will 直 display the same since they have the same code point, but different number of strokes in japabese and chinese.
Aren't they putting the disunified characters into the U+2xxxx plane now?
Han unification is generally seen as a bad choice in retrospect, but it was something Unicode had to do when it looked like 2^16 codepoints were all they were going to get.
Never heard of that, but I would appreciate if all the characters with different glyphs had different codepoints. Do you have a source? Do you know what happens to the "unified" code-points?
It is true to some extent. While 青 and 靑 have different codepoints, there are plenty of characters of the same codepoint that are rendered differently depends on the language specificed:
Han characters that are traditionally viewed as variants of one another, or that are simplified from more complex logograms (such as 龜, which was simplified into 亀 in Japan and 龟 in mainland China) tend to have different codepoints, but the stylistically different ones usually belong to the same codepoint.
Han Unification "rules" were an inconsistent mess, but I do know that in Japanese 靑 was at one time a printer's simplification of 青, so you could find either in texts, and the Consortium tended to encode a character separately if you could find printed examples of both in the same language.
For CJK characters, they unified all semantically similar han-characters, even when they have visual forms that are quite different between Japanese, Chinese and Korean.
If you want to write Japanese and Chinese in the same document, you need to mark up the section to tell the system that renders it, to render different visual forms for similar codepoints depending on whether they are used in Japanese or Chinese.