Bug 55824 - misplacement of two vowels when mixed with one specific leg in Khmer script (under harfbuzz-ng)
Summary: misplacement of two vowels when mixed with one specific leg in Khmer script (...
Status: RESOLVED WONTFIX
Alias: None
Product: HarfBuzz
Classification: Unclassified
Component: src (show other bugs)
Version: unspecified
Hardware: Other All
: medium normal
Assignee: Behdad Esfahbod
QA Contact:
URL:
Whiteboard:
Keywords:
Depends on:
Blocks:
 
Reported: 2012-10-10 07:42 UTC by nirvn.asia
Modified: 2012-12-03 15:55 UTC (History)
1 user (show)

See Also:
i915 platform:
i915 features:

Attachments
harfbuzz-ng (left) and old pango (right); row #1 and #2 show the vowels placed too low under harfbuzz-ng (21.87 KB, image/png)
2012-10-10 07:43 UTC, nirvn.asia 		Details
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Description nirvn.asia 2012-10-10 07:42:15 UTC 
While checking the latest harfbuzz-ng committed to firefox this Oct 9, I noticed that two Khmer vowels (ុ [SRA O] and ូ [SRA OO]) are placed too low when associated with one specific leg (្រ [CHHUNG RO]).

When rendered with the pango engine (which firefox used under linux until Oct 9), the two vowels are correctly placed.

I've made a quick testcase that provides the Khmer script bits to test this placement issue, as well as an associated screenshot of how it should look, here: http://licadho-cambodia.org/mapnik/testcase-refine.html
Comment 1 nirvn.asia 2012-10-10 07:43:39 UTC 
Created attachment 68388 [details]
harfbuzz-ng (left) and old pango (right); row #1 and #2 show the vowels placed too low under harfbuzz-ng
Comment 2 nirvn.asia 2012-10-10 08:12:17 UTC 
Just to clear possible confusion, row #3 and #4 are rendering properly under both harfbuzz-ng and pango. These were added to make sure the two vowels are properly placed with obstructing legs and the "non-obstructing" leg CHHUNG RO.
Comment 3 Behdad Esfahbod 2012-11-13 03:11:38 UTC 
Hi Mathieu,

We looked into that too.  That's a limitation of our fallback positioning logic.  It's not really possible to improve it.  We can either do fallback positioning, which has some limitations, or not do fallback positioning, which has more problems.  We decided that if people want perfect positioning they should add a GPOS table, so we are not going to improve the case you raised.

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