Re: lineHeight="normal"

Thank you. I will check [1] http://www.w3.org/TR/2006/REC-xsl11-20061205/#area-line

Hope I can understand :-)

best regards,
Uchimura

On Thu, 6 Sep 2012 17:25:25 +0900
Glenn Adams <glenn@skynav.com> wrote:


> On Thu, Sep 6, 2012 at 2:21 PM, Kouichi Uchimura <Kouichi.Uchimura@jp.sony.com> wrote:
> Hi,
>> 
>> I'm studying tts:lineHight attribute and have one comment.
>> ?(I checked issue58.)
>> 
>> Current text defines:
>> If the value of this attribute is normal, then the initial value of the style property must be considered to be the same as the largest font size that applies to any descendant element.
>> I'd like to confirm that
>> ?whether "any descendant element" includes the affected element itself
>> or not.
>> My interpretatin is the affected element itself is not included.
>> 
>> Examples are...
>> ?<p region="r1" tts:lineHeight="normal" tts:fontSize="64px" begin="0s"
>> end ="1s">
>> ? this<br/>
>> ? span<tts:fontSize="16px">
>> ? ? is<br/>
>> ? span<tts:fontSize="14px">
>> ? ? example
>> </p>
>> This case, lineHeight is 64px.
>> ?text node "this" and br elem will be enclosed by anonymous span and its
>> fontSize is 64px.
>> So, max font size of descendants is 64px.
>> 
>> On the other hand,
>> ?<p region="r1" tts:lineHeight="normal" tts:fontSize="64px" begin="0s"
>> end ="1s">
>> ? span<tts:fontSize="16px">
>> ? ? this is<br/>
>> ? span<tts:fontSize="14px">
>> ? ? example
>> </p>
>> This case, lineHeight is 16px.
>> 
>> Is above understanding correct?
>> ?If not, suggest to change the text to as like...
>> "to be the same as the largest font size that applies to any descendant
>> element (includes the affected element itself)."


I'm not sure about the origin of the current language, which differs from both CSS and XSL-FO. XSL-FO has a number of line-stacking-strategy values (max-height, font-height, line-height) which affect the height of the line allocation rectangle. The nominal CSS behavior is obtained when stack strategy is line-height. I suspect that the current language in TTML was an attempt to simply the extremely complex description found in [1], which, every time I read it, I can't quite get my head around its meaning. Some times when I read it I think I understand it, but then I read something else related to this topic in XSL-FO that abrogates my understanding.


[1]?http://www.w3.org/TR/2006/REC-xsl11-20061205/#area-line








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Kouichi Uchimura <Kouichi.Uchimura@jp.sony.com>