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Issue 591346 link

Starred by 27 users

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Status: Available
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Pri: 2
Type: Bug

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issue 549571



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Fallback path fails to find font for certain combining marks, diacritics sequences

Project Member Reported by drott@chromium.org, Mar 2 2016

Issue description

In  issue 549569  and the remaining part of 445028 the problem is that our fallback lookup code only does lookup for one character. 

There are various issues with this:
Sequences like
DIGIT ONE + COMBINING KEYCAP will lead to a lookup of "DIGIT ONE", which is almost in every font, but no emoji font will be found.

The combining mark face from  issue 549569  ╰̩̩̩̩̩̻̍̍̍̍̍̊●̩̩̩̩̩̩̩̻̍̍̍̍̍̍̍̊ᴗ̩̩̩̩̩̩̩̩̩̩̪̺̍̍̍̍̍̍̍̍̍̍̆̑●̩̩̩̩̩̩̩̻̍̍̍̍̍̍̍̊╯̩̩̩̩̩̩̻̍̍̍̍̍̊   will not work because only the base characters are found, not all the combining marks.

The sequence a⃗ (a with combining arrow) does not always resolve to the right font because only "a" is looked up, but not the arrow.

We need to improve our fallback path to handle such cases.

 

Comment 1 by drott@chromium.org, Mar 2 2016

Cc: e...@chromium.org kojii@chromium.org js...@chromium.org tkonch...@chromium.org
 Issue 549569  has been merged into this issue.

Comment 2 by drott@chromium.org, Mar 2 2016

Cc: ajha@chromium.org wangxianzhu@chromium.org
 Issue 445028  has been merged into this issue.

Comment 3 by drott@chromium.org, Mar 2 2016

Cc: rnimmagadda@chromium.org
 Issue 335674  has been merged into this issue.

Comment 4 by drott@chromium.org, Mar 2 2016

 Issue 335674  contains a good test case for combining half marks:
http://chris.improbable.org/experiments/browser/combining-half-marks/

Comment 5 by drott@chromium.org, Mar 2 2016

 Issue 48025  has been merged into this issue.

Comment 6 by drott@chromium.org, Mar 7 2016

 Issue 592332  has been merged into this issue.

Comment 7 by drott@chromium.org, Mar 15 2016

Cc: drott@chromium.org
 Issue 594658  has been merged into this issue.

Comment 8 by drott@chromium.org, Mar 15 2016

 Issue 594658  has a test case for Korean tonemarks: 
data:text/html; charset=utf-8, <span style="font-family:Noto Sans CJK KR;">한〮</span>

Comment 9 by js...@chromium.org, Mar 15 2016

A bit more involved test case for Korean tone marks where the 'base glyph' comes from a three character sequence instead of one character. 

data:text/html; charset=utf-8, <span style="font-family:Noto Sans CJK KR;">ᄒᆞᇰ〮</span>



Comment 10 by drott@chromium.org, Apr 27 2016

 Issue 606173  has been merged into this issue.

Comment 11 by drott@chromium.org, Apr 27 2016

Another useful test case in  issue 606173 :
http://sriku.org/bugs/combining-char-bug/

Re #11: On Windows there does not actually seem to be any font that could handle combining marks on Tamil text. It seems Edge and FF do combine Nirmala UI with Times New Roman to display something remotely similar to what's requested - but do not do grapheme cluster based font fallback.

Root cause for tests in 8 and 9 have been identified to be separate,  issue 594658  had been unmerged. I believe our only cases in which this still goes wrong are those for mathematical / symbol cases with combining arrow on top etc.

Comment 14 by drott@chromium.org, Jul 18 2016

 Issue 565732  has been merged into this issue.
 Issue 651018  has been merged into this issue.
 Issue 651018  has examples for Hebrew letters with Arabic diacritics.
Cc: kkaluri@chromium.org
 Issue 677681  has been merged into this issue.
 Issue 719196  has been merged into this issue.
 Issue 729833  has been merged into this issue.
Cc: hdodda@chromium.org
 Issue 730855  has been merged into this issue.

Comment 21 by drott@chromium.org, Aug 21 2017

Cc: robertshield@chromium.org abdulsyed@chromium.org behdad@chromium.org
 Issue 755255  has been merged into this issue.
Project Member

Comment 22 by sheriffbot@chromium.org, Aug 21

Labels: Hotlist-Recharge-Cold
Status: Untriaged (was: Available)
This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot
Status: Available (was: Untriaged)
Cc: phanindra.mandapaka@chromium.org
 Issue 917835  has been merged into this issue.

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