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Re: [css3-fonts] Behdad's Feedback on CSS Fonts Module Level 3 Editor's Draft 5 April 2010

From: Chris Lilley <chris@w3.org>
Date: Fri, 20 Aug 2010 00:52:23 +0200
Message-ID: <1038712975.20100820005223@w3.org>
To: Behdad Esfahbod <behdad@behdad.org>
CC: Jonathan Kew <jonathan@jfkew.plus.com>, John Daggett <jdaggett@mozilla.com>, Thomas Phinney <tphinney@cal.berkeley.edu>, "Tab Atkins Jr." <jackalmage@gmail.com>, <www-style@w3.org>, Brad Kemper <brad.kemper@gmail.com>
On Friday, August 20, 2010, 12:22:39 AM, Behdad wrote:

BE> On 08/19/10 16:53, Chris Lilley wrote:
>> On Thursday, August 19, 2010, 8:08:16 PM, Behdad wrote:

>> BE> On 08/17/10 05:12, Jonathan Kew wrote:
>>>> In that case, I suggest we should have a new property called "font-extend" that would take a scaling factor to be applied to the glyphs and metrics in the x-direction (or rather, along the direction of text layout, so for vertical text it would apply in the y-direction). A font-extend value of less than 1.0 would actually compress the glyphs, of course. And negative values ought to reflect the glyphs and reverse the text direction, so that <span style="font-extend: -1.0">mirror writing</span> becomes easy to express.

>> BE> Watch out!  Mirroring text that way has bidi implications.  Mirror an RTL span
>> BE> and it should be processed as LTR during bidi now. 

>> Well, no. It would look like rtl text in a mirror. With the glyphs backwards, and everything.

BE> Not when you mix it.  Believe me.  

I understand the point you are making about how bidi works. Believe me too. 

(description of bidi, omitted)

But you fail to understand the point I was making. 

Here is an experiment. Take a printed item, containing Latin text. Hold it to a mirror. look in the mirror. You see Latin text mirrored, with all the glyphs back to front, and progressing right to left.

Is this RTL text?

No, it is LTR text that has been mirrored. It is an optical effect. It has nothing to do with RTL or bidi text, whatsoever.

If you like, take some printed bidi text (mixed Arabic and French, for example) and hold it to a mirror.

Again, the glyphs are all mirrored, and if your mirror makes the reflection of the printed text magically re-arrange itself, I will be amazed.

Because, again, this is not turning RTL text into LTR text. It is optically mirroring (or if you like, transforming) RTL or Bidi text into mirrored RTL or Bidi text.

 Chris Lilley   Technical Director, Interaction Domain                 
 W3C Graphics Activity Lead, Fonts Activity Lead
 Co-Chair, W3C Hypertext CG
 Member, CSS, WebFonts, SVG Working Groups
Received on Thursday, 19 August 2010 22:53:31 UTC

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