The Arabic letter "ha" does not appear correctly with some web fonts

NEW
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Status

()

4 years ago
4 years ago

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(Reporter: over68, Unassigned)

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35 Branch
x86_64
Windows 7
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Firefox Tracking Flags

(Not tracked)

Details

(Reporter)

Description

4 years ago
The Arabic letter "ha" does not appear correctly with some web fonts.

Testcase https://dl.dropboxusercontent.com/u/95157096/85f61cf7/ge5de3bwr3.html

Screenshot https://dl.dropboxusercontent.com/u/95157096/85f61cf7/sqhx3rwx3d.png


Steps to reproduce:

1. Close Firefox, if it is open.
2. Go to "Control Panel", open "Region and Language", change the "Format" to Arabic, then press OK, see https://dl.dropboxusercontent.com/u/95157096/85f61cf7/1iu1zssfl3.png.
3. Open Firefox, then go to https://dl.dropboxusercontent.com/u/95157096/85f61cf7/ge5de3bwr3.html.


The problem occurs with harfbuzz enabled.

See https://dl.dropboxusercontent.com/u/95157096/85f61cf7/bvk3htubts.png.
(Reporter)

Updated

4 years ago
Flags: needinfo?(jfkthame)
(Reporter)

Comment 1

4 years ago
I can reproduce this problem since the Nightly build 2011-08-15, Regressed by bug 667166.
(Reporter)

Updated

4 years ago
Component: General → Layout: Text
This is a problem with the implementation of the 'locl' (Localized Forms) feature in the font. It didn't show up under Uniscribe shaping, because Uniscribe doesn't support localized forms.[1] With harfbuzz enabled, however, we support localized forms, and this font has an arab:ARA lookup that changes the HA glyph before normal Arabic shaping has a chance to take effect.

You can reproduce the problem without setting the Region & Language format to Arabic if you include the lang="ar" attribute in the testcase, so that the Arabic-language forms are used instead of the "default" OpenType language system.

Explicitly disabling the localized forms feature, with

  -moz-font-feature-settings: "locl" off;

in the CSS, would work around this issue.


[1] See http://www.microsoft.com/typography/OpenTypeDev/arabic/intro.htm#tags: "Currently, the Uniscribe engine only supports the "default" language for each script."
Flags: needinfo?(jfkthame)
Hardly surprising; I expect Linotype used the same basic pattern for their features across a whole range of Arabic fonts. The same response still applies: what you're seeing is the effect of the localized-forms feature for the Arabic language (OpenType tag 'ARA'), which uniscribe didn't apply, but harfbuzz does.
Status: UNCONFIRMED → NEW
Ever confirmed: true
(Reporter)

Comment 5

4 years ago
This bug has been fixed in bug 1108616.
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