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

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
>