[Webkit-unassigned] [Bug 101239] New: Add layout test for handling of ZWJ/ZWNJ in Indic scripts

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=101239

           Summary: Add layout test for handling of ZWJ/ZWNJ in Indic
                    scripts
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Linux
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: jshin at chromium.org
                CC: bashi at chromium.org


A recent switch to harfbuzz resolved a host of problems in Chrome Linux including the handling of ZWJ/ZWNJ in Indic scripts. We may not have a comprehensive layout tests for them, though. 

Below is taken from http://crbug.com/45840#c47

-------------------
See Following cases of ZWJ(Zj - U+200D) and ZWNJ(Zn - U+200C) behavior is found in Malayalam and Devanagari:


1)
C Vi Zj C which expects grouping in following sequence: (C Vi Zj C)
if that failed, consider: (C Vi Zj) (C) --> (C Vi) (Zj) (C) --> (C) (Vi) (Zj) (C)

2)
C Zj Vi C --> (C) (Zj Vi C) --> (C) (Zj) (Vi C) --> (C) (Vi) (Zj) (C)

3)
C Vi Zn C -->  (C) (Vi) (Zj) (C)

Similarly, 
4)
C Vi Zj --> (C Vi Zj) --> (C Vi) (Zj) --> (C) (Vi) (Zj)

5)
Zj Vi C --> (Zj Vi C) --> (Zj) (Vi C) --> (Vi) (Zj) (C)



Zj and Zn alone needs to be suppressed, if possible.

Sinhala script is not looked at.

In case of Malayalam, (C Vi Zj C) is not mandatory, but nice to have.

In Indic fonts, Zj(200D) is found typically as part of the look-ahead operator.
Arabic font does not seems to have any rules based on Zj.

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