Incorrect shaping (GSUB and GPOS) on Safari macOS and iOS up to and including 26.3.1

[MattMatic]

Defect Report

Noto Sans Bengali Regular versions 3.000 to 3.011 produce incorrect shaping on macOS and iOS up to and including 26.3.1 compared to HarfBuzz (v12.3.0).

Other notes

• macOS 26.4 and iOS 26.4 now shape the same as HarfBuzz
• Older devices that cannot run macOS/iOS 26 are potentially worse (can provide more data as required)
• macOS can use Chrome which uses HarfBuzz, but Chrome/Firefox/Opera on an iOS before 26.4 does not resolve the issue (it looks like CoreText is used for all iOS services 🫢)

Steps to demonstrate

Used my tool "Will It 'Buzz? on macOS and iOS with a large Bengali word list to find the differences quickly and provide the renders.

Sample words

These ten are taken from the set of 1808 words that failed (more examples can be provided).

• BLUE = HarfBuzz
• RED = Apple macOS / iOS

0028 অনুমানলব্ধ Estimated

0029 অনুরক্ততা Affection

0031 অন্তর্দৃষ্টিপূর্ণ Insightful

0033 অপরিপূর্ণ Incomplete

0053 অবির্ভূত Unexpected

0056 অব্যক্তিত্বহীন Impersonal

0077 আগমুহূৰ্ত্তত In advance

0119 আর্থ্‌রাইটিস Arthritis

0123 আৱিৰ্ভাৱ Appearance

1783 হেনৰী Henry

[MattMatic]

Created a little shell script to call hb-shape (14.1.0) and output with ot and coretext shapers.

Hopefully this will assist.

অনুমানলব্ধ 0985,09a8,09c1,09ae,09be,09a8,09b2,09ac,09cd,09a7

OpenType        : [a-beng=0+893|na-beng=1+602|uMatra-beng=1@-172,0+0|ma-beng=3+612|aaMatra-beng=3+266|na-beng=5+602|la-beng=6+731|b-beng.half2=7+689|baphala-beng.alt4=9@-572,76+0|dha-beng.part=9@-252,49+0|headline-beng.250=9@-250,0+0]
Core Text 26.3.1: [a-beng=0+893|na-beng=1+430|uMatra-beng=1+172|ma-beng=3+612|aaMatra-beng=3+266|na-beng=5+602|la-beng=6+731|ba-beng=7+424|halant-beng=7+172|dha-beng=9+596]
Core Text 26.4  : [a-beng=0+893|na-beng=1+430|uMatra-beng=1+172|ma-beng=3+612|aaMatra-beng=3+266|na-beng=5+602|la-beng=6+731|b-beng.half2=7+117|baphala-beng.alt4=9@0,76+320|dha-beng.part=9@0,49+2|headline-beng.250=9+250]

অনুরক্ততা 0985,09a8,09c1,09b0,0995,09cd,09a4,09a4,09be

OpenType        : [a-beng=0+893|na-beng=1+602|uMatra-beng=1@-172,0+0|ra-beng=3+596|t_ta-beng=4+910|ka-beng.arm2=6@-365,23+0|headline-beng.200=6@-200,0+0|ta-beng=7+707|aaMatra-beng=7+266]
Core Text 26.3.1: [a-beng=0+893|na-beng=1+430|uMatra-beng=1+172|ra-beng=3+596|t_ta-beng=4+545|ka-beng.arm2=6@0,23+165|headline-beng.200=6+-165|ka-beng.arm2=7@0,23+365|aaMatra-beng=7+266]
Core Text 26.4  : [a-beng=0+893|na-beng=1+430|uMatra-beng=1+172|ra-beng=3+596|t_ta-beng=4+545|ka-beng.arm2=6@0,23+165|headline-beng.200=6+200|ta-beng=7+707|aaMatra-beng=7+266]

অন্তর্দৃষ্টিপূর্ণ 0985,09a8,09cd,09a4,09b0,09cd,09a6,09c3,09b7,09cd,099f,09bf,09aa,09c2,09b0,09cd,09a3

OpenType        : [a-beng=0+893|n-beng.half3=1+756|ta-beng.blws=3@-769,52+0|da-beng=4+553|rVocalicMatra-beng=4@-153,-10+0|reph-beng=4@-323,0+0|iMatra-beng.ttaAlt1=8+266|ss_tta-beng.noflag=8+531|tta-beng.flagIMatra3=8@-592,0+0|pa-beng=12+716|uuMatra-beng=12@-172,0+0|nna-beng=14+620|reph-beng=14@-152,0+0]
Core Text 26.3.1: [a-beng=0+893|n-beng.half3=1+-13|ta-beng.blws=3@0,52+769|da-beng=4+400|rVocalicMatra-beng=4@0,-10+-170|reph-beng=4+323|iMatra-beng.ttaAlt1=8+729|reph-beng.altAuLength=8@0,32+-463|ss_tta-beng.noflag=8+-61|tta-beng.flagIMatra3=8+592|pa-beng=12+544|uuMatra-beng=12+172|nna-beng=14+620|uni200B=14+0]
Core Text 26.4  : [a-beng=0+893|n-beng.half3=1+-13|ta-beng.blws=3@0,52+769|da-beng=4+400|rVocalicMatra-beng=4@0,-10+-170|reph-beng=4+323|iMatra-beng.ttaAlt1=8+266|ss_tta-beng.noflag=8+-61|tta-beng.flagIMatra3=8+592|pa-beng=12+544|uuMatra-beng=12+172|nna-beng=14+468|reph-beng=14+152]

অপরিপূর্ণ 0985,09aa,09b0,09bf,09aa,09c2,09b0,09cd,09a3

OpenType        : [a-beng=0+893|pa-beng=1+716|iMatra-beng=2+266|ra-beng=2+596|pa-beng=4+716|uuMatra-beng=4@-172,0+0|nna-beng=6+620|reph-beng=6@-152,0+0]
Core Text 26.3.1: [a-beng=0+893|pa-beng=1+716|iMatra-beng=2+690|reph-beng=2@0,-3+-424|ra-beng=2+596|pa-beng=4+544|uuMatra-beng=4+172|nna-beng=6+620|uni200B=6+0]
Core Text 26.4  : [a-beng=0+893|pa-beng=1+716|iMatra-beng=2+266|ra-beng=2+596|pa-beng=4+544|uuMatra-beng=4+172|nna-beng=6+468|reph-beng=6+152]

অবির্ভূত 0985,09ac,09bf,09b0,09cd,09ad,09c2,09a4

OpenType        : [a-beng=0+893|iMatra-beng=1+266|ba-beng=1+596|bha-beng=3+701|uuMatra-beng.round=3@-249,52+0|reph-beng=3@-357,0+0|ta-beng=7+707]
Core Text 26.3.1: [a-beng=0+893|iMatra-beng=1+690|reph-beng=1@0,-3+-424|ba-beng=1+596|bha-beng=3+452|uuMatra-beng.round=3@0,52+249|uni200B=3+0|ta-beng=7+707]
Core Text 26.4  : [a-beng=0+893|iMatra-beng=1+266|ba-beng=1+596|bha-beng=3+452|uuMatra-beng.round=3@0,52+-108|reph-beng=3+357|ta-beng=7+707]

অব্যক্তিত্বহীন 0985,09ac,09cd,09af,0995,09cd,09a4,09bf,09a4,09cd,09ac,09b9,09c0,09a8

OpenType        : [a-beng=0+893|ba-beng=1+596|ya-beng.pstf=1+270|iMatra-beng.long02=4+266|t_ta-beng=4+910|ka-beng.arm2=4@-365,23+0|headline-beng.200=4@-200,0+0|t-beng.half=8+688|baphala-beng.alt2=8@-491,-46+0|ha-beng=11+534|iiMatra-beng=11+266|na-beng=13+602]
Core Text 26.3.1: [a-beng=0+893|ba-beng=1+596|ya-beng.pstf=1+270|iMatra-beng.long02=4+266|t_t-beng.half=4+528|ka-beng.arm2=6@0,43+0|ka-beng.arm2=8@0,43+-293|baphala-beng.alt2=8@0,-100+455|ha-beng=11+534|iiMatra-beng=11+266|na-beng=13+602]
Core Text 26.4  : [a-beng=0+893|ba-beng=1+596|ya-beng.pstf=1+270|iMatra-beng.long02=4+266|t_ta-beng=4+545|ka-beng.arm2=6@0,23+165|headline-beng.200=6+200|t-beng.half=8+197|baphala-beng.alt2=8@0,-46+491|ha-beng=11+534|iiMatra-beng=11+266|na-beng=13+602]

আগমুহূৰ্ত্তত 0986,0997,09ae,09c1,09b9,09c2,09f0,09cd,09a4,09cd,09a4,09a4

OpenType        : [aa-beng=0+1159|ga-beng=1+646|ma-beng=2+612|uMatra-beng=2@-172,0+0|ha-beng=4+534|uuMatra-beng.round=4@-297,93+0|t_ta-beng=6+710|reph-beng=6@-258,0+0|ta-beng=11+707]
Core Text 26.3.1: [aa-beng=0+1159|ga-beng=1+646|ma-beng=2+440|uMatra-beng=2+172|ha-beng=4+237|uuMatra-beng.round=4@0,93+297|t_ta-beng=6+452|reph-beng=6+93|ka-beng.arm2=11@0,23+165|headline-beng.200=11+200]
Core Text 26.4  : [aa-beng=0+1159|ga-beng=1+646|ma-beng=2+440|uMatra-beng=2+172|ha-beng=4+237|uuMatra-beng.round=4@0,93+297|t_ta-beng=6+452|reph-beng=6+258|ta-beng=11+707]

আর্থ্‌রাইটিস 0986,09b0,09cd,09a5,09cd,200c,09b0,09be,0987,099f,09bf,09b8

OpenType        : [aa-beng=0+1159|tha-beng=1+645|halant-beng=1@-172,0+0|space=1+0|reph-beng=1@-151,0+0|ra-beng=6+596|aaMatra-beng=6+266|i-beng=8+534|iMatra-beng.ttaAlt1=9+266|ddha-beng=9+547|tta-beng.flagIMatra1=9@-641,0+0|sa-beng=11+623]
Core Text 26.3.1: [aa-beng=0+1159|tha-beng=1+473|halant-beng=1+172|space=1+0|reph-beng=1+0|ra-beng=6+596|aaMatra-beng=6+266|i-beng=8+534|iMatra-beng.ttaAlt1=9+266|ddha-beng=9+-94|tta-beng.flagIMatra1=9+641|sa-beng=11+623]
Core Text 26.4  : [aa-beng=0+1159|tha-beng=1+473|halant-beng=1+172|space=1+0|reph-beng=1+0|ra-beng=6+596|aaMatra-beng=6+266|i-beng=8+534|iMatra-beng.ttaAlt1=9+266|ddha-beng=9+-94|tta-beng.flagIMatra1=9+641|sa-beng=11+623]

আৱিৰ্ভাৱ 0986,09f1,09bf,09f0,09cd,09ad,09be,09f1

OpenType        : [aa-beng=0+1159|iMatra-beng=1+266|ralowerdiagonal-beng=1+596|bha-beng=3+701|reph-beng=3@-357,0+0|aaMatra-beng=3+266|ralowerdiagonal-beng=7+596]
Core Text 26.3.1: [aa-beng=0+1159|iMatra-beng=1+690|reph-beng=1@0,-3+-424|ralowerdiagonal-beng=1+596|bha-beng=3+701|uni200B=3+0|aaMatra-beng=5+266|ralowerdiagonal-beng=7+596]
Core Text 26.4  : [aa-beng=0+1159|iMatra-beng=1+266|ralowerdiagonal-beng=1+596|bha-beng=3+344|reph-beng=3+357|aaMatra-beng=5+266|ralowerdiagonal-beng=7+596]

হেনৰী 09b9,09c7,09a8,09f0,09c0

OpenType        : [eMatra-beng.init=0+361|ha-beng=0+534|na-beng=2+602|ramiddlediagonal-beng=3+596|iiMatra-beng=3+266]
Core Text 26.3.1: [eMatra-beng.init=0+361|ha-beng=0+382|ka-beng.arm2=2@0,14+112|headline-beng.250=2+250|ramiddlediagonal-beng=3+596|iiMatra-beng=3+266]
Core Text 26.4  : [eMatra-beng.init=0+361|ha-beng=0+534|na-beng=2+602|ramiddlediagonal-beng=3+596|iiMatra-beng=3+266]

[simoncozens]

Seems like macOS had a bug and now it's fixed?

[MattMatic]

That is true for devices that support 26.4 (both macOS and iOS).

For the older devices that cannot upgrade, these issues persist for web pages, and for iOS cannot even be resolved by using Chrome. 🥺 (Including iOS 18.7.7 that was just released to patch vulnerabilities)
FWIW, Noto Sans Bengali 2.003 rendered fine (though I do realise the engineering has changed a lot).

I'm not sure what Core Text has an issue with, and/or whether the features can be adjusted to accommodate Apple? Happy to investigate and help as needed 🙂

[simoncozens]

I'm not a big fan of messing with fonts to accommodate Apple's bugs. They should fix their problems, not me.

[lianghai]

This seems to be related to HB’s lack of per-cluster limitation in some earlier versions? See #32 (comment). I hope Apple hasn’t been blindly following HB for its behavior…

[MattMatic]

This seems to be related to HB’s lack of per-cluster limitation in some earlier versions? See #32 (comment). I hope Apple hasn’t been blindly following HB for its behavior…

That's a good thought...
I tested these words against HarfBuzz 11.0.1 up to 12.3.0 and they all render correctly (i.e. no change on Noto Sans Bengali 3.011).

I would agree with Simon about Apple, except that this causes problems for a large number of users on the web (since iOS mandates WebKit AFAICS), and they won't fix anything but serious security flaws on older iOS versions 😔

Will keep digging to see if I can uncover any other knowledge, but open to other ideas and suggestions.
Thanks!

[khaledhosny]

Created a little shell script to call hb-shape (14.1.0) and output with ot and coretext shapers.

You might want to also use hb-shape’s --ned option when comparing CoreText output to get absolute glyph positions, since HarfBuzz and CoreText do relative glyph positions rather differently.

[codayon]

I'm using takumi, an OG generator and while using the latest version of Noto Sans Bengali, I faced similar issues.

I'm on Windows 11. At the top, it's the latest variable font, on the bottom it's the older variable font.