Unnecessary kerning between a white-space/symbol and a CJK character

[ftake]

Scribus in CTL repository inserts an unnecessary implicit space (kerning) before/after CJK characters if the previous/next character is:

• a white space such as tab, thin space, other than normal space
• a symbol such as period, colon, parenthesis, question, exclamation

For example, as shown in the screen shot attached, English words and Japanese words does not align with a tab.

For now, I cannot explain the correct criteria whether an implicit space is necessary or not. We need to make a list of character classes which requires that implicit space.

[Fahad-Alsaidi]

@ftake thanks for report, what is the way forward to fix this problem? Do we just want delete any implicit space?

[ftake]

Instead of using !IsCJK(), we should make a new function like IsSpaceSeparatedLangChars(). The new functions return true if a given character is one of language in which words is separated with spaces.

I think [a-zA-Z0-9] is enough for the first implementation. I think it covers 99% of normal Japanese documents.

[Fahad-Alsaidi]

I think [a-zA-Z0-9] is enough for the first implementation. I think it covers 99% of normal Japanese documents.

This will not work with Arabic letters

[Fahad-Alsaidi]

I pushed a commit to fix this bug. However, I covered only in SpecialChars::isCJKImplicitNotNeeded:

• General Punctuation range
• tab
• Non-breaking space

please test and if you want add more char to list, please tell me.

[ftake]

The use of isCJKImplicitNotNeeded() is inversed, isn't it?

I have a local patch, which uses a white list approach (which contains [a-zA-Z0-9] for now) for a magazine published in the end of this year.

As you say, it should contains Arabic as well as other Latin characters. What is interesting, MS Word does not insert kerning between CJK and Arabic.

In black list approach, isCJKImplicitNotNeeded() should contain ASCII and the other symbols.

BTW: the code block for JISX 4051 contains several bugs from the original patch:
https://sites.google.com/a/borndigital.jp/scribus/home/line-composition

I will make the specification more clear after I finish writing the magazine.

[Fahad-Alsaidi]

If I understand you right. The only case for implicit space is when CJK char have CJK char next to it. This means it should not insert implicit space when: 1- beginning of text. 2- any char not CJK including Latin, Arabic, punctuation chars ..... 3- end of text. Am I right?

[Fahad-Alsaidi]

I revert isCJKImplicitNotNeeded() code and I used isCJK() instead.
The new code will cover anything not CJK such as Latin, Arabic, punctuation chars .....