[Webkit-unassigned] [Bug 240279] New: Traditional Mongolian script characters incorrectly oriented

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=240279

            Bug ID: 240279
           Summary: Traditional Mongolian script characters incorrectly
                    oriented
           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

Lines of text in the Traditional Mongolian script run vertically from top to bottom of the page. Lines flow from left to right. The script is cursive, meaning that the characters join along the vertical centre line. Here is an example:

https://user-images.githubusercontent.com/4839211/167632640-cb805b08-59a1-4c73-a28f-b47f7048f153.png

Note the orientation of the glyphs.


Specs:
css-writing-modes-4 provides the writing-modes property. The vertical-lr value is designed to display Traditional Mongolian text as expected.


Tests & results:
i18n test suite, Vertical text, Vertical-LR, Glyphs (https://w3c.github.io/i18n-tests/results/writing-mode-vertical#lr_glyphs)

Results

    Gecko: ✅ Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:100.0) Gecko/20100101 Firefox/100.0

    Blink: ✅ Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.54 Safari/537.36

    WebKit: ❌ Rotates lines appropriately, but doesn't display characters in the correct orientation and doesn't join them up (see the left-hand line below). Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.4 Safari/605.1.15

    https://user-images.githubusercontent.com/4839211/105961907-09663500-6077-11eb-9034-13afb495de68.png

    To get this to work in WebKit you need to add text-orientation: sideways to the CSS, which should not be necessary, and is not needed for Gecko and Blink browsers.


This issue is being tracked by the W3C at https://w3c.github.io/mlreq/gap-analysis/#issue39_vertical_text

Another (long) bug was raised in 2013 and ground to a halt in 2014 (8 years ago!).  I'm starting a new bug because i want to just focus on making Mongolian look correct and getting WebKit to be interoperable with other browsers from a content author perspective. (See https://bugs.webkit.org/show_bug.cgi?id=112488)

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