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From: Peter Kelly <pmkelly@apache.org>
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Subject: Re: ODF to HTML
Date: Mon, 1 Jun 2015 23:43:35 +0700
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(apologies if this is a duplicate - I sent from the wrong email address =
before)

> On 31 May 2015, at 7:09 pm, Ian C <ian@amham.net =
<mailto:ian@amham.net>> wrote:
>=20
> We also need to take into account the style hierarchy. I see from some =
of the CSS documentation that there are mechanisms in place to manage =
that but have not looked in detail. Any advice Peter?

First, some general comments - what I recommend is to first build up a =
custom data structure representing all the styles which can later be =
queried when needed, e.g. when you encounter an element in content.xml =
that has a particular style associated with it.

In the Word filter, there are two classes used for this purpose: =
WordSheet and WordStyle (the former being a collection of the latter). =
These are defined in WordSheet.h and WordSheet.c. Early in the =
conversion process, the filter goes through the XML document containing =
the styles and builds up this data structure. This results in the code =
being able to deal with the styles at a higher-level of abstraction than =
examining the DOM tree of styles.xml directly.

A while ago I made a start on the same thing for ODF - there=E2=80=99s =
ODFSheet and ODFStyle classes defined for the same purpose. So a good =
next step for tackling styles would be to traverse the DOM tree of =
styles.xml and populate this data structure, creating a new ODFStyle =
object for each style in the document, and adding them to the (single) =
ODFSheet object for the document. This data structure could then be used =
to generate the CSS text, as is done in the Word filter.

> I just generated to div tags do we want that? Mapping to h1... hn =
could be a better way but not sure how to really map the correct heading =
styles to the hn.

In the case of ODF, the information about what header to map to is =
(usually) available more directly than in OOXML. Both specs refer to it =
as the =E2=80=9Coutline level=E2=80=9D. In an ODF document, heading =
outline levels start from 1 (just like HTML), but you also have the =
distinction between <text:h> and <text:p> elements, so you can know =
whether something is a heading or a regular paragraph.

When encountering a <text:h> element, you can determine the outline =
level from the attribute, e.g.:

<text:h text:style-name=3D"Heading_20_1" text:outline-level=3D"1">Headline=
 One</text:h>

So here the value =E2=80=981=E2=80=99 is sufficient information to =
indicate that you need to create a h1 element. The style-name attribute =
is Heading_20_1, so the corresponding CSS would need to be:

h1.Heading_20_1 {
}

and similarly for other levels, e.g.

h2.Heading_20_2 {
}

Note that, as with your existing code, this would be generated =
separately from the content itself, solely based on the information in =
styles.xml, for the non-automatic styles.

So I suggest separating buildCSS_Styles into two separate functions: One =
which populates the CSSSheet object associated with the package (that =
is, package->sheet, which I think is already created), and another which =
examines the ODFSheet object and populates the CSSSheet object.

=E2=80=94
Dr Peter M. Kelly
pmkelly@apache.org

PGP key: http://www.kellypmk.net/pgp-key =
<http://www.kellypmk.net/pgp-key>
(fingerprint 5435 6718 59F0 DD1F BFA0 5E46 2523 BAA1 44AE 2966)


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