RE: Default rendering of Combining diacritical marks

From: Peter Constable (
Date: Tue Mar 07 2006 - 00:53:26 CST

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    Strictly speaking, it is not a bug but rather a limitation in functionality - not a supported feature in that version. In fact, the functionality is supported in part.


    You need three things for such combinations to display correctly: (1) OpenType fonts with special tables needed to support mark positioning, (2) support in the platform for Latin combining marks, and (3) applications that support Latin combining marks. Windows XP/SP2 includes the second item, and at least some of the apps that ship with Windows XP/SP2 (e.g. Notepad, Wordpad, IE) meet the bar for item 3. What's missing is item 1: the fonts that ship with XP/SP2 do not have the tables needed to position combining marks.


    All of the Windows core fonts that will ship with Windows Vista have been updated to include support for combining marks as well as full Unicode 4.1 Latin character coverage (and Greek, etc. - all the fonts that the core fonts already support are updated to 4.1). There are also third-party fonts you can use on XP/SP2 to support combining marks, such as the Doulos and Charis fonts from SIL.






    From: [] On Behalf Of saqqara
    Sent: Monday, March 06, 2006 3:20 AM
    Subject: Default rendering of Combining diacritical marks


    Windows XP/SP2. When I use COMBINING DOT BELOW with an OpenType font without specific support for the combination (e.g. current release of Times New Roman for most diacritic latin forms) the dot is placed to the bottom left of the character box rather than the centre (e.g. try d or D with the combining dot).


    Am I correct in categorising this as a Windows text rendering bug or am I missing a more subtle point about how Unicode software is expected to deal with this situation?



    Bob Richmond


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