1403166 - Khmer Unicode Renders Incorrectly using macOS system fonts

Status: RESOLVED FIXED

(Core :: Layout: Text and Fonts, defect, P3)

Description

[[e-mail]]

Attachment: firefox.png

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/604.1.38 (KHTML, like Gecko) Version/11.0 Safari/604.1.38

Steps to reproduce:

Browse to a Khmer website (like https://plovpit.com )



Actual results:

The title bar will not render Khmer correctly in Firefox on Mac OS Sierra


Expected results:

Khmer should render correctly as it does in Chrome and Safari

Comment 1

[[e-mail]]

Attachment: Khmer rendered correctly in Safari

Comment 2

[Jonathan Kew [:jfkthame]]

Attachment: Prefer HarfBuzz shaping over Core Text for the macOS Khmer fonts that include both AAT and OpenType Layout tables, as the latter seem to work better

Normally, for complex-script fonts on macOS, we route the shaping through Core Text so that Apple's AAT fonts will work properly. Unfortunately, this doesn't seem to be a good option for the Khmer fonts they're now shipping, which also have OpenType layout tables; we'll do better to allow harfbuzz to handle them.

Comment 3

[Jonathan Kew [:jfkthame]]

Hmm, I wonder if this is actually another example like bug 1370927, where the AAT fonts require an "unexpected" feature to be enabled in order to shape correctly. I'll do a quick experiment to check that; if so, that would probably be the better workaround to apply.

Comment 4

[Jonathan Kew [:jfkthame]]

Attachment: For Khmer AAT fonts, enable the Line Initial Smart Swashes feature, which is (incorrectly) required for some vowels to render properly

Yep, this appears to fix the Khmer rendering, just like the Indic split-vowel cases. Sad, but at least it's simple.

Comment 5

[Jonathan Kew [:jfkthame]]

Comment on attachment 8916637 [details] [diff] [review]
Prefer HarfBuzz shaping over Core Text for the macOS Khmer fonts that include both AAT and OpenType Layout tables, as the latter seem to work better

Obsoleting this patch; I think the fix in gfxCoreTextShaper is a better approach, as it means we're using the same rendering path for these fonts as Apple does in their own software.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/060b6a8b02f6
For Khmer AAT fonts, enable the Line Initial Smart Swashes feature, which is (incorrectly) required for some vowels to render properly. r=jrmuizel

Comment 7

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/060b6a8b02f6