These are mentioned on http://www.unicode.org/charts/PDF/U1EE00.pdf referred by the MathML 3 recommendation, but absent from their suggested operator dictionary. I don't think any math font supports them yet.
The following operators stretch based on the width of the text that is displayed below or above them.
1EEF0 ARABIC MATHEMATICAL OPERATOR MEEM WITH HAH WITH TATWEEL
• used in Arabic mathematics to denote summation
• stretched at the tatweel
→ 2211 ∑ n-ary summation
1EEF1 ARABIC MATHEMATICAL OPERATOR HAH WITH DAL
• used in Persian mathematics to denote limits
• stretched between the hah and the dal
Created attachment 286710 [details]
*** Bug 122296 has been marked as a duplicate of this bug. ***
Created attachment 286853 [details]
Adding a test and fixing a coding error with explicit prefix. I'll add a test for horizontal stretchiness tomorrow.
Created attachment 286963 [details]
Comment on attachment 286963 [details]
View in context: https://bugs.webkit.org/attachment.cgi?id=286963&action=review
> +// The following two non-BMP characters are handled separately so that the arrays 'dictionary' and
> +// 'horizontalOperators' can use UChar instead of UChar32 and avoid an increase of memory footprint.
I don’t think this is the right call. The additional memory footprint is about 2kB. We should keep the code simple instead.
(In reply to comment #5)
> I don’t think this is the right call. The additional memory footprint is
> about 2kB. We should keep the code simple instead.
OK, I'll rewrite a simpler patch then.
Created attachment 287248 [details]
Committed r205111: <http://trac.webkit.org/changeset/205111>