[Fontconfig] Re: fontconfig support to exclude glyphs from fonts

[Jay Hobson]

Keith Packard wrote:

>On Thu, 2006-06-29 at 10:43 -0700, Jay Hobson wrote:
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>>Keith,
>>
>>While I can see the need for a ban on unicode codepoint sets, I think 
>>many end users will find that horribly difficult to use and set up. With 
>>the patch that I am providing, you can accomplish the same basic goal 
>>without nearly as much hardship. I suspect it is easier to look up what 
>>languages a font supports, than what the unicode codepoint set is.
>>    
>>
>
>That's a good point. Having the ability to *also* edit the language set
>offered by a font makes good sense.
>
>I think what I was focused on was the notion that we should (finally)
>look at editing the data about the available fonts instead of trying to
>work around broken data during the match phase.
>
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>>Additionally, if you ban an entire language from a font, then the 
>>language will be displayed with a different font and have a better 
>>chance of looking consistent. If you ban a codepoint set, unless you get 
>>the entire language coverage, you run the risk of having two fonts 
>>display your text, which would likely look bad.
>>    
>>
>
>Right. Let's work on a font pattern editing mechanism and then do both
>code point and language editing. That should fix both problems nicely.
>
>The main reason for a code point ban is to elide latin glyphs from
>non-latin fonts -- TrueType nearly insists that all fonts include latin
>glyphs, which makes no sense for many non-latin fonts, and which often
>results in really ugly latin glyphs being included.
>  
>
One interesting twist to this, and the reason that I designed the patch 
the way that I did, is that some of these same fonts that include Latin 
glyphs can have latin characters that are matched nicely to the other 
languages contained in the font (not often). IE: size, thickness, etc. 
However, the latin only contains either Serif or Sans-Serif glyphs, and 
the other language is often needed for both Sans and Serif coverage. 
This leaves a latin that might be nice to have in one instance, and not 
in the other. Hence the reason that you would want to dynamically enable 
and disable languages from a font. For one alias it would be good, for 
the other, it would be bad. Right now, there is no mechanism for 
detailing language coverage by alias. The patch includes such a 
mechanism which adds some additional value to fontconfig.

>The language ban will work better where multiple languages share the
>same code point range.
>
>Good ideas; let's see what we can manage.
>
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