Open Radar

 
Summary:
The Unicode standard (v5.0 onward), in section 5.8 "Newline Guidelines", subsection "Line Separator and Paragraph Separator", provides explicit guidance on how text rendering systems should differ in their handling of the characters LINE SEPARATOR (U+2029) and PARAGRAPH SEPARATOR (U+2028). (Link here: http://www.unicode.org/versions/Unicode8.0.0/ch05.pdf )

Cocoa ignores the guidance regarding LINE SEPARATOR, and treats it identically to PARAGRAPH SEPARATOR.

In particular, if you define an NSParagraphStyle with a paragraphSpacing, and you initialize an NSAttributedString that uses a LINE SEPARATOR character, then Cocoa will apply the paragraph spacing to the vertical separation produced by the LINE SEPARATOR, just as if it were a PARAGRAPH SEPARATOR.

This is noncompliant with Unicode's recommendation, and with the entire point of the LINE SEPARATOR character, which is for it to mark a line break that is not a paragraph break.

Steps to Reproduce:
1. Paste the enclosed swift file into a playground
2. Notice the values at the very bottom of the playground. The heights returned by the `intrinsicContentSize` of the two labels `twolineICSP2` and `twoParaICSP2` are equal, when they should be different. One uses LINE SEPARATOR, one uses PARAGRAPH SEPARATOR. The paragraphs style has been configured with explicit non-zero distinct values for `lineSpacing` and `paragraphSpacing`, so these two labels should not have the same heights.



Expected Results:
Expect to see that only `lineSpacing` is applied to the lines separated by LINE SEPARATOR, but `lineSpacing`

Actual Results:
 `lineSpacing` and `paragraphSpacing` are applied to the lines separated by LINE SEPARATOR, just like with PARAGRAPH SEPARATOR or LINE FEED.

Version:
iOS 9 at least.

attachment also at : https://gist.github.com/algal/17c73d28e562ccc07372