Bug 135510

Summary: Incorrect rendering of Unicode combining half marks on OS X
Product: WebKit Reporter: Chris Adams <chris>
Component: TextAssignee: Nobody <webkit-unassigned>
Severity: Normal CC: ap, ebrahim, mitz, mmaxfield, ned
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: Macintosh   
OS: OS X 10.9   
URL: http://chris.improbable.org/experiments/browser/combining-half-marks/

Description Chris Adams 2014-08-01 09:58:35 PDT
One of our users reported a problem with the text displayed on http://www.wdl.org/en/item/10643/. The author name on that page uses the Unicode combining half marks COMBINING LIGATURE LEFT HALF and COMBINING LIGATURE RIGHT HALF (U+FE20, U+FE21)

According to the Unicode 6.0 specification – see page 235-236 of http://www.unicode.org/versions/Unicode6.0.0/ch07.pdf – two adjacent marks should combine into a single curve. 

On OS X, the behaviour depends whether font substitution occurred so e.g. the current WebKit Nightly will display the tests at http://chris.improbable.org/experiments/browser/combining-half-marks/ correctly only for Arial but most other fonts will display incorrectly. 

Recent versions of Internet Explorer on Windows 7 or later display correctly in all cases. Chrome and Firefox are also inconsistent depending on the OS and font combinations.

Previously reported to Apple as rdar://13105608
Comment 1 mitz 2014-08-01 21:08:17 PDT
Also happens in TextEdit with the same font, so likely not a WebKit issue.
Comment 2 Ebrahim Byagowi 2017-09-16 02:03:11 PDT
This seem to work now.