Bug 276074

Summary: Decomposed Unicode text font selection can result in poor rendering
Product: WebKit Reporter: Tal <tal.avraham12>
Component: TextAssignee: Nobody <webkit-unassigned>
Status: NEW    
Severity: Normal CC: ap, bfulgham, fantasai.bugs, simon.fraser, vitor.roriz, webkit-bug-importer, zalan
Priority: P2 Keywords: InRadar
Version: Safari 17   
Hardware: Mac (Apple Silicon)   
OS: Unspecified   
See Also: https://bugs.webkit.org/show_bug.cgi?id=303066
Attachments:
Description Flags
letter is bold although font weight is 400
none
reduction none

Tal
Reported 2024-07-01 07:32:02 PDT
Writing Einäscherung the bug recreates- thats because the ä appears to be constructed using two separate characters: a plain lowercase 'a' followed by a combining diaeresis (¨). This is called a decomposed form, where the umlaut is not part of the 'a' character but is added separately. Writing Einäscherung the bug doesn't reproduce- thats because the ä is written using a single character, which is the typical way to write it in German. This character is a lowercase letter 'a' with an umlaut (two dots above it). safari has specific rendering issues with combining diacritical marks, especially when these marks are handled differently in the rendering engine compared to precomposed characters.
Attachments
letter is bold although font weight is 400 (106.60 KB, image/png)
2024-07-01 07:33 PDT, Tal 		no flags
Details
reduction (995 bytes, text/html)
2024-07-02 13:59 PDT, Alexey Proskuryakov 		no flags
Details
View All Add attachment proposed patch, testcase, etc.
Tal
Comment 1 2024-07-01 07:33:41 PDT
Created attachment 471782 [details] letter is bold although font weight is 400
Alexey Proskuryakov
Comment 2 2024-07-01 08:59:04 PDT
> Writing Einäscherung the bug recreates > Writing Einäscherung the bug doesn't reproduce Thank you for the report. Could you please provide more detailed steps to reproduce (which website to open, which input method to select, which exact keys to press)? The general problem area is fairly clear, but this really depends on which fonts are specified in CSS, and also it's unclear what cases you are contrasting.
Tal
Comment 3 2024-07-01 23:34:01 PDT
Hi, thanks! You can open this site- https://talavr1.wixsite.com/check-87 there you can see the difference between single character and decomposed form. Do you need any more details to understand better the bug? Thanks!
Alexey Proskuryakov
Comment 4 2024-07-02 13:59:51 PDT
Created attachment 471798 [details] reduction Thank you, attaching a reduction.
Radar WebKit Bug Importer
Comment 5 2024-07-02 14:00:08 PDT
<rdar://problem/130994567>
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