Bug 220536

Summary:

Multi-codepoint CJK grapheme clusters are not oriented correctly in vertical writing mode

Product:

WebKit

Reporter:

Myles C. Maxfield <mmaxfield>

Component:

New Bugs

Assignee:

Myles C. Maxfield <mmaxfield>

Status:

RESOLVED FIXED

Severity:

Normal

CC:

lmoura, webkit-bug-importer, zalan

Priority:

Keywords:

InRadar

Version:

WebKit Nightly Build

Hardware:

Unspecified

OS:

Unspecified

See Also:

https://bugs.webkit.org/show_bug.cgi?id=220680

Attachments:

Description	Flags
Patch	zalan: review+

Myles C. Maxfield

Reported 2021-01-12 01:01:05 PST

Multi-codepoint CJK grapheme clusters are not oriented correctly in vertical writing mode

Attachments
Patch (4.63 KB, patch) 2021-01-12 01:03 PST, Myles C. Maxfield	zalan: review+	Details Formatted Diff Diff
View All Add attachment proposed patch, testcase, etc.

Myles C. Maxfield

Comment 1 2021-01-12 01:03:01 PST

Created attachment 417438 [details] Patch

Myles C. Maxfield

Comment 2 2021-01-12 01:03:04 PST

<rdar://problem/70633887>

Myles C. Maxfield

Comment 3 2021-01-12 14:58:04 PST

Investigating the Windows failure now.

Myles C. Maxfield

Comment 4 2021-01-12 16:55:14 PST

Committed r271425: <https://trac.webkit.org/changeset/271425>

Lauro Moura

Comment 5 2021-01-15 08:27:51 PST

GTK/WPE renders the glyph correctly but with a slightly different positioning, ditto for Firefox 85 and Chromium 87. The same occurs for single codepoints. Does the spec require them to to be layout exactly the same (i.e. single grapheme in vertical and horizontal modes) or it's something open and the test could be tweaked to work in GTK/WPE?

Myles C. Maxfield

Comment 6 2021-01-15 10:20:36 PST

(In reply to Lauro Moura from comment #5) > GTK/WPE renders the glyph correctly but with a slightly different > positioning, ditto for Firefox 85 and Chromium 87. The same occurs for > single codepoints. > > Does the spec require them to to be layout exactly the same (i.e. single > grapheme in vertical and horizontal modes) or it's something open and the > test could be tweaked to work in GTK/WPE? They don’t *have* to be exactly the same. However, the em box is usually a perfect square, so it would be good to at least determine where the offset comes from in GTK/WPE. One would expect that rotating a perfect square by 90deg would lead to an identical rendering.

Lauro Moura

Comment 7 2021-01-15 18:50:19 PST

(In reply to Myles C. Maxfield from comment #6) > (In reply to Lauro Moura from comment #5) > > GTK/WPE renders the glyph correctly but with a slightly different > > positioning, ditto for Firefox 85 and Chromium 87. The same occurs for > > single codepoints. > > > > Does the spec require them to to be layout exactly the same (i.e. single > > grapheme in vertical and horizontal modes) or it's something open and the > > test could be tweaked to work in GTK/WPE? > > They don’t *have* to be exactly the same. However, the em box is usually a > perfect square, so it would be good to at least determine where the offset > comes from in GTK/WPE. One would expect that rotating a perfect square by > 90deg would lead to an identical rendering. For GTK/WPE in this test the box seems to be slightly rectangular (111x100) and slightly offset (-6,0 and 0,-6, depending on the orientation). I've opened bug220680 to track it.

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