[Webkit-unassigned] [Bug 269186] New: Unicode characters with "variation selectors" are not rendered in the iPhone Safari browser (webkit) with iOS 17.3

Mon Feb 12 03:57:18 PST 2024

https://bugs.webkit.org/show_bug.cgi?id=269186

            Bug ID: 269186
           Summary: Unicode characters with "variation selectors" are not
                    rendered in the iPhone Safari browser (webkit) with
                    iOS 17.3
           Product: WebKit
           Version: Safari 17
          Hardware: iPhone / iPad
                OS: iOS 17
            Status: NEW
          Severity: Major
          Priority: P2
         Component: Text
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: jeffreyx at gmail.com
                CC: fantasai.bugs at inkedblade.net, vitor.roriz at apple.com

Created attachment 469819

  --> https://bugs.webkit.org/attachment.cgi?id=469819&action=review

Screen capture from an issue case in iOS 17.3 (bad)

Environment: iPhone 14/15, iOS 17.3

Description: Unicode characters with "Variation Selectors Supplement" code can be rendered correctly in all iPhone before iOS 17.3 . But in iOS 17.3, these characters become "blank" in iPhone.
Fonts with Variation Selectors are used for displaying alternative Chinese characters reprensenting different pronoucation and different stroke styles.

Issue URL(HTML version of this bug report):
https://toneoz.com/ivsdemo/index.html
https://forums.developer.apple.com/forums/thread/746406

Screen capture from an issue case in iOS 17.3 (bad):
https://toneoz.com/ivsdemo/bad.jpg

Screen capture from a good case in other OS (good):
https://toneoz.com/ivsdemo/good.jpg

Reproduce steps:
1. Download a "Variation Selectors" supported TTF font
https://github.com/ButTaiwan/bpmfvs/releases/download/v1.400/BpmfZihiKaiStd.zip
2. Unzip the ttf font file "BpmfZihiKaiStd-Regular.ttf" from the zip to a folder
3. In the same folder, create an file "index.html" with the following content:
<head>
<meta charset="utf-8">
<style>
@font-face { font-family: zihaibpmf; src: url('BpmfZihiKaiStd-Regular.ttf'); }
</style>
</head>
<body>
<table class="redboder" border>
<tr><td>
Unicode Text
</td><td style="font-family:zihaibpmf;">一</td><td style="font-family:zihaibpmf;">一��</td><td style="font-family:zihaibpmf;">一��
</td></tr><tr><td>       
Unicode Hex Code</td><td>
0x4E00</td><td>0x4E00 0xE01E1</td><td>0x4E00 0xE01E2
</td></tr>
</table>
</body>

4. Upload the files to a web server
5. Browser the "index.html" with an iOS 17.3 iPhone 14 or 15
6. There should be a character displayed in each table cells. But with iOS 17.3, two of the cells are blank.

Reference: opensource IVS TTF font github: "BpmfZihiKaiStd" TTF Font file download : https://github.com/ButTaiwan/bpmfvs/releases/download/v1.400/BpmfZihiKaiStd.zip

"Variation Selectors Supplement" is supported by all other OS (Windows, Android, Linux, old iOS, macOS), see :

wiki : Variation Selectors Supplement https://en.wikipedia.org/wiki/Variation_Selectors_Supplement

wiki : Variant form (Unicode) https://en.wikipedia.org/wiki/Variant_form_(Unicode)

...Variation Selectors Supplement is a Unicode block containing additional variation selectors beyond those found in the Variation Selectors block. These combining characters are named variation selector-17 (for U+E0100) through to variation selector-256 (U+E01EF), abbreviated VS17 – VS256.

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