[Webkit-unassigned] [Bug 237953] New: Greek uppercase transforms fail for some characters

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=237953

            Bug ID: 237953
           Summary: Greek uppercase transforms fail for some characters
           Product: WebKit
           Version: Safari 15
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: ishida at w3.org
                CC: bfulgham at webkit.org, simon.fraser at apple.com,
                    zalan at apple.com

Created attachment 454826

  --> https://bugs.webkit.org/attachment.cgi?id=454826&action=review

1. tonos not removed

Converting text to uppercase requires special behaviour for some Greek characters.

Specs: The text-transform property is defined in CSS Text Module Level 3.
https://www.w3.org/TR/css-text-3/#text-transform-property

The spec includes mention of the need for user agents to tailor the transforms for a particular language:

>   The UA must use the full case mappings for Unicode characters, including any conditional casing rules, as defined in the Default Case Algorithms section of The Unicode Standard. [UNICODE](https://www.w3.org/TR/css-text-3/#biblio-unicode) If (and only if) the content language of the element is, according to the rules of the document language, known, then any appropriate language-specific rules must be applied as well. These minimally include, but are not limited to, the language-specific rules in Unicode’s SpecialCasing.txt.

Tests & results: i18n test suite, case conversion, Greek These tests focus on monotonic Greek as used for modern texts. https://w3c.github.io/i18n-tests/results/case-conversion#greek

Results:
-    Gecko: ✅ Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:98.0) Gecko/20100101 Firefox/98.0
-    Blink: ✅ Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.51 Safari/537.36
-    Webkit: ✅❌ The basic conversions work, but the special Greek rules are not applied. See below. Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.3 Safari/605.1.15

Issues with WebKit:

1.    transform: uppercase doesn't cause Greek words that are all uppercase to lose tonos.
2.    transform: uppercase doesn't convert diphthongs with tonos on the first character so that the tonos is removed but a dialytika is added above the second character in the diphthong.
3.    text-transform: uppercase should cause a disjunctive eta in a Greek sentence keeps its tonos diacritic, but the test is inconclusive because none of the other tonos marks is removed.

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