Re: tts:rubyReserve + tts:lineHeight (issue #779)

> How is this different from assigning a length value for lineHeight

An author does not need to account for the presence of ruby text when
specifying tts:lineHeight. Instead, as I understand the specifications, the
processor automatically grows the line area height if the computed value of
tts:lineHeight is not sufficient to accommodate the ruby text (of the font
size specified by the author) -- see attached examples.

Why should the author have to set the line height manually when using
tts:rubyReserve?

Best,

-- Pierre

[image: 0.png]

On Mon, May 21, 2018 at 1:00 PM Glenn Adams <glenn@skynav.com> wrote:

> How is this different from assigning a length value for lineHeight in a
> non-ruby paragraph and not knowing whether the fonts used will fit the
> line? I think you could say exactly the same thing there:
>
> >It is therefore impossible for the author to accurately specify a
> <length>, and the default value might not be appropriate.
>
> On Mon, May 21, 2018 at 11:59 AM, Pierre-Anthony Lemieux <pal@sandflow.com
> > wrote:
>
>> Hi Cyril, Glenn et al.,
>>
>> The following is based on my working on implementing tts:rubyReserve in
>> imscJS.
>>
>> tts:rubyReserve is intended to reserve room to contain inline areas
>> generated by ruby annotations and emphasis marks, regardless of whether the
>> latter are present at a given instant in time.
>>
>> As currently specified, the amount of room reserved is explicitly
>> specified by the author as a <length>, or, if left unspecified, set to a
>> default value equal to 50% of the used value of the tts:lineHeight
>> applicable to the p element.
>>
>> I see a fundamental challenges with this approach:
>>
>> (a) neither tts:ruby nor tts:textEmphasis specify the amount of room
>> needed for ruby annotations and emphasis marks, respectively -- the amount
>> of room is left to the implementation. It is therefore impossible for the
>> author to accurately specify a <length>, and the default value might not be
>> appropriate.
>>
>> (b) the default value is not sufficient if the author specifies a font
>> size for ruby annotations that is different from the ruby base font size.
>>
>> I suggest exploring the following tweak to the semantics of
>> tts:rubyReserve:
>>
>> """
>> The implementation reserves room for ruby annotations and emphasis marks
>> assuming:
>> - the font size of the base text is the same as that of the <p>
>> - the font size of the annotation/emphasis mark is specified by the
>> <length> or, if the <length> is not specified, computed according
>> to 10.2.21.1
>> """
>>
>> I will be on the road and unavailable for the next two TTWG calls. I am
>> however available today and tomorrow to discuss live​, and will be
>> available over email.
>>
>> Best,
>>
>> -- Pierre
>>
>
>