Re: [TTML2] tts:{width,height} rename

ipd = inline progression dimension
bpd = block progression dimension

they are the writing mode relative counterparts to width and height; the
problem with the latter is that they are strongly associated with absolute
axes (horizontal and vertical), while the former {ipd,bpd} don't suffer
from that association

it also requires less spec text and results in less confusion in the spec,
since in all places at present (except for line height), width and height
are interpreted in an absolute sense independent of writing mode

tts:{ipd,bpd} are used to specify constraints on the dimensions of areas
generated by content elements

On Tue, Jan 27, 2015 at 7:37 AM, David Singer <singer@apple.com> wrote:

> yikes
>
> it’s nice if the terms are readable.  Linewidth and Lineheight have some …
> recognition, albeit mostly in writing systems that use horizontal lines
> assembled into vertical blocks.
>
> ipd and bpd are directions, not measurements, aren’t they? and they don’t
> exactly roll off the tongue or leap to mind in terms of recognizability
>
> > On Jan 26, 2015, at 1:01 , Glenn Adams <glenn@skynav.com> wrote:
> >
> > The use of width and height as writing mode relative properties is
> confusing. Change their names to ipd and bpd, abbreviations for inline
> progression dimension and block progression dimension, respectively, and
> document convention that width and height (as well as horizontal and
> vertical) are always absolute and not writing mode relative. The only
> exception being that 'height' in lineHeight remains writing mode relative,
> i.e., specifies the nominal bpd of a line area.
> >
> > Change image to use tts:extent instead of the former tts:{width,height}
> in order to use absolute axes in expressing explicit image dimensions.
> >
> > Addressed above comments in [1].
> >
> > [1] https://dvcs.w3.org/hg/ttml/rev/69877acd9380
>
> David Singer
> Manager, Software Standards, Apple Inc.
>
>
>