Looking for the Big O, not just some TT's

by Michael S. Kaplan, published on 2007/12/26 10:16 -05:00, original URI: http://blogs.msdn.com/b/michkap/archive/2007/12/26/6868799.aspx


The question over on the OpenType list was:

Dear All,
 
I've been developing my first Opentype Font lately. It is an Arabic Naskh style font that is fully compliant with the rules of Naskh Calligraphy. So Far, things have been going quite well.
 
The only problem I have run into is that, when I ship the font out of VOLT, and then install it, regardless of whether I give it the TTF or OTF extension, Windows seems to insist on assigning it the TTF icon, rather than the OTF Icon.
 
In Adobe Acrobat, It appears as an opentype font.
 
Does anyone have any idea where I might be going wrong ?
Or is there some adjustment I need to make in the Font Design software, prior to loading it into VOLT ?

Many thanks Beforehand.

I'll provide a bit of art so you know what we're talking about:

The question itself was answered there by Chris Fynn....

Before I started quoting it here, I suddenly remembered he also answered this question on the Unicode List back in end of 2004. I dug up his response from my archives....

His previous answer covered quite a bit of ground, so I thought I'd just capture his words here:

The "O" icon simply indicates the font has been digitally signed. Though the digital signature field is defined in the OpenType specification the presence of a digital signature in a font does not necessarily indicate that the font has any other OpenType features. Many OpenType fonts with advanced features have not been digitally signed and consequently do not display the "O" icon in Windows.

OpenType is a superset of TrueType - so all Windows fonts which conform to the TrueType specification could also be called OpenType. If it says OpenType in the sample window it doesn't mean very much.

If you want to be able to find out more useful information about Windows fonts use Microsoft's Font Properties Extension:
<
http://www.microsoft.com/typography/TrueTypeProperty21.mspx>
If the Font Properties Extension is installed you can then R-click on a font file in Windows Explorer and bring up a "Properties" dialog - in this dialog there is a "Features" panel which will tell you whether or not there are any OpenType GSUB and GPOS tables in the font.

When people ask whether your application supports OpenType fonts, what I expect they mean is "Does your application make use of the GSUB And GPOS lookups in OpenType fonts?". Supporting OT GSUB and GPOS lookups is *necessary* for proper display of Unicode data for complex scripts (Arabic, Devanagari, Bengali, Tamil, Tibetan, Khmer, Sinhala etc.)in Windows (and many Linux) applications.

If your application supports TrueType but does not support the OpenType lookups you will still see some glyphs using the OpenType font but these will probably not be the correct ones as your application won't be showing the correct contextual forms necessary for languages written in these scripts.

Large "Pan-Unicode" fonts like "Arial Unicode MS" usually do not contain proper OpenType tables and ligatures for *all* the scripts the font covers. For example "Arial Unicode MS" and "Code 2000" contain glyphs for Tibetan script but they *do not* contain the OpenType GSUB and GPOS lookups necessary to display Tibetan correctly.

If a Windows application needs to properly display Unicode text for languages such as Hindi, Tamil, Bengali, Nepali, Sinhala, Arabic, Urdu and so on then it probably needs to support OpenType GSUB and GPOS lookups.

For Latin script, OpenType lookups are mainly used to place combining diacritics properly and for advanced typographic features such as true small saps, Swashes, automatic ligatures, old-style figures and do on.

The rules that Windows for determining which glyph to show here even today is obviously kind of arbitrary and not really the idel way to determining any of the real questions that a reasonable person might have about the underlying font.

But in fairness it is just an icon -- and icons really don't tend to capture a ton of information.

The source of the confusion here is that there are specific definitions that help determine what is an OpenType font, and generally speaking a customer will come in with some but not all of those questions (this is why the issues in Microsoft *does* support OpenType! are so easy to define yet ultimately unsatisfying.

Perhaps the answer would be to have a few different icons here -- maybe always the TrueType icon, but with some specific overlays for the key requirements from both the Microsoft and Adobe sides of the OpenType equation?

 

This post broght to you by(U+0f5d, aka TIBETAN LETTER WA)


# Josh on 27 Dec 2007 11:49 AM:

Amazing how much power people ascribe to a grid of 48x48 pixels, innit? :-)

fp on 4 May 2008 2:30 PM:

Help! im desperate, these should be a walk on the park for someone that knows about these things... i need the following written in naskh...  "...the life of this world is nothing but a provision of vanities." Qur'an 3.185.

thanks

Michael S. Kaplan on 4 May 2008 3:26 PM:

Sorry, that is a bit outside of my area of expertise....


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