RE: NNBSP-MVS Impact

Does anyone have contact with a Harfbuzz engineer that can give us an understanding on how Harfbuzz handles the character immediately preceeding the MVS/NNBSP?
Greg


From: Greg Eck
Sent: Tuesday, June 30, 2015 12:46 AM
To: 'public-i18n-mongolian@w3.org'
Subject: NNBSP-MVS Impact


With reference to http://r12a.github.io/scripts/mongolian/variants.html



As we start the discussion of Mongolian variants, I think it is

important to look at the means of implementing the NNBSP and the MVS

first. There is considerable variation here. If we can understand how

each font implements these two areas, it may bring understanding of

why our fonts differ in shaping in these two contexts. I am presenting

two documents for discussion dealing with the NNBSP and the MVS model.

*If we could have a description of how Harfbuzz, Apple and other

rendering engines interpret the character preceding/following the

NNBSP/MVS that would be helpful.* These descriptions will be added

into the NOTES section of each chart. The attached chart shows the

model used in the Microsoft Universal Shaping Engine.



Once we have agreed upon the two models, we will start with

The U+1820-A (initial/medial )and then proceed to the

other five similarly affected code-points U+1828 (medial/final), U+182C

(medial/final), U+182D (medial/final), U+1835 (medial/final), U+1836

(medial/final). A premise that I start with is that "Mongolian font

implementation does not always follow grammatical rules" - case in

point is the U+182C final which is not grammatical, but seems to be the

implementation of choice for two glyphs in most of the fonts on display.



Greg