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Re: [css-text] Arabic letters connecting between elements with display: inline

From: Jonathan Kew <jfkthame@gmail.com>
Date: Tue, 27 May 2014 18:07:55 +0100
Message-ID: <5384C66B.9050700@gmail.com>
To: Richard Ishida <ishida@w3.org>, Asmus Freytag <asmusf@ix.netcom.com>, Lina Kemmel <LKEMMEL@il.ibm.com>, Matitiahu Allouche <matitiahu.allouche@gmail.com>
CC: 'Behdad Esfahbod' <behdad@behdad.org>, 'fantasai' <fantasai.lists@inkedblade.net>, public-i18n-bidi@w3.org, 'WWW International' <www-international@w3.org>, www-style@w3.org
On 27/5/14 17:55, Richard Ishida wrote:
> On 27/05/2014 17:43, Asmus Freytag wrote:
>> I think inserting markup between parts of an obligatory (or intended)
>> ligature is a mistake by the author and requiring complex support to
>> force this to "work" is counter productive.
>>
>> On the contrary, the expectation should be clear that ligatures are
>> broken, so that authors can get visual feedback and proof their work.
>
> The problem I see with this is that one of the many possible ligatures
> like lam-meem depends on the font used.  If the content author changes
> the font or a device changes the font from one that doesn't support
> lam-meem ligatures to one that does you don't want to have to go change
> all the markup or disable the effect.
>
> This may however been a different kettle of fish from a lam-alif
> ligature, since the latter makes it more difficult to separate which
> part of the glyph represents which underlying character (at least in the
> form that looks like a crossed ribbon). I suspect, though I haven't
> tested it, that in general non-lam-alif ligatures such the lam-meem type
> keep the glyph representations of the underlying characters separate
> enough to allow differential colouring.

It varies, depending on stylistic considerations and implementation 
choices by the font developer. There are plenty of fonts where lots of 
two- and three-letter (or sometimes longer) Arabic sequences are 
replaced by single glyphs.

>
> A quick test on Firefox shows that it breaks a lam-alif ligature if
> there is markup between the lam and alif,

It should be able to form a ligature across markup such as a <span> 
boundary, provided the font (face) being used doesn't change. How useful 
this is may be open to question, but you can see a couple of examples of 
how this can look, assuming the appropriate fonts are installed, with a 
testcase like this in Firefox:

data:text/html,
   <div style="font:100px/100px Arial; color:red">
    %26%23x644;<span style="color:blue">%26%23x627;</div>
   <div style="font:120px/100px Scheherazade; color:red">
    %26%23x644;<span style="color:blue">%26%23x627;</div>

The Arial example shows the ligature simply painted in two halves 
(divided vertically down the middle), while the Scheherazade example 
more properly shows the component parts.

And that very example appears, incidentally, in an image at
http://wiki.arabeyes.org/Developing_Arabic_fonts. :)

JK
Received on Tuesday, 27 May 2014 17:08:25 UTC

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