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Re: EPUB Accessibility: Discovery of the Writing Direction (DRAFT 1.0)

From: MURATA <eb2mmrt@gmail.com>
Date: Sat, 5 Dec 2020 23:08:33 +0900
Message-ID: <CALvn5EAohxnw4HViRu_3qTrjkZPEiwksws1+1O4BjoobQHFZdQ@mail.gmail.com>
To: Koji Ishii <kojiishi@gmail.com>
Cc: Jens Tröger <jens.troeger@light-speed.de>, Ivan Herman <ivan@w3.org>, W3C EPUB3 Community Group <public-epub3@w3.org>, W3C Publishing Community Group <public-publishingcg@w3.org>, Richard Ishida <ishida@w3.org>, Florian Rivoal <florian@rivoal.net>
> Some questions on the discoverability topic:
> 1. Can a publication be found for both D1 and D2 in your doc
> <https://1drv.ms/w/s!An5Z79wj5AZBgtUx_1os2PNRrYkDjA?e=v9qSpH>? I think
> yes for publications that can change the writing-mode but wanted to confirm.
Exactly.  See the note in 5.1.

> 2. If a non-switchable publication contains both writing-modes, how should
> it be found? As you know, a publication may have vertical chapters but book
> covers/chapter title pages/appendixes may be horizontal. Is it up to
> authors which writing-mode is "primary"?

I am aware that such publications exist.  In such cases,
I think that authors should indicate which direction is

> 3. I remember we had a discussion on page progression direction. CSS
> defines the page progression direction
> <https://drafts.csswg.org/css-writing-modes-3/#page-direction>, but it is
> only for an XHTML document (spine), and the page progression of a
> publication may be different, or an EPUB publication may contain mixed page
> progressions. Do you remember if we defined that, or did we leave it
> undefined, in the current EPUB spec?

The following paragraphs are extracted from EPUB Packages 3.2.
We might want to improve them on the basis of our experiences.
EPUB 3.3 is being developed by the EPUB 3 WG now.

The page-progression-direction attribute sets the global direction in which
the content flows. Allowed values are ltr (left-to-right), rtl (right-to-left)
and default. When the default value is specified, the Author is expressing
no preference and the Reading System can choose the rendering direction.
The default value *MUST* be assumed when the attribute is not specified. In
this case, the reading system *SHOULD* choose a default
page-progression-direction value based on the first language element.

Although the page-progression-direction attribute sets the global flow
direction, individual Content Documents and parts of Content Documents
*MAY* override
this setting (e.g., via the writing-mode CSS property). Reading Systems
*MAY* also provide mechanisms to override the default direction (e.g.,
buttons or settings that allow the application of alternate style sheets).

Reading Systems *MUST* ignore the page progression direction defined in
pre-paginated <https://www.w3.org/publishing/epub/epub-packages.html#layout>
Content Documents. The page-progression-direction attribute defines the
flow direction from one fixed-layout page to the next.

> A minor point: if the word "discovery" in your doc has a specific meaning
> in an existing spec, it is helpful if you can link the word to the
> definition.

Noted.   Will think about this.

Received on Saturday, 5 December 2020 14:09:27 UTC

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