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List: calligra-devel
Subject: Re: a new library for traversing odf files and a new export filter
From: Sebastian Sauer <mail () dipe ! org>
Date: 2013-03-26 9:32:58
Message-ID: 51516B4A.6050205 () dipe ! org
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On 03/26/2013 02:51 PM, Lassi Nieminen wrote:
> Hola,
>
> On Mon, Mar 25, 2013 at 8:12 PM, Inge Wallin <inge@lysator.liu.se
> <mailto:inge@lysator.liu.se>> wrote:
>
> On Monday, March 25, 2013 17:54:53 matus.uzak@gmail.com
> <mailto:matus.uzak@gmail.com> wrote:
> > Hi,
> >
> > sorry for not discussing earlier, but I did not have much free
> time last
> > two weeks.
> >
> > I think we should continue the parser type discussion in order
> to also
> > improve state of things in libmsooxml. What we have there is a PULL
> > parser. And I identified the following problems (Would be cool
> is Lassi
> > could check those):
> >
> > 1. OOXML sometimes requires us to run the parser twice at one
> element in
> > order to first collect selected information required to convert
> the content
> > of child elements.
> >
> > 2. There are situations when conversion of the 1st child of the root
> > element requires information from the last child of the root
> element.
>
> It would be interesting to see some examples of these two issues.
>
>
> As an example : in pptx files, in slides,
> there can be text which is specified to use theme color lt1
>
> Don't remember the exact syntax, but something like
> <p>
> <rPr "color" = "lt1"/>
> <r>Hejsan</r>
> </p>
>
> Then as the last element of that slide there may or may not be
> <clrMap "lt1" = "bg1" ...../> // or something similar
>
> Which means that lt1 should be interpreted to be bg1 for this
> particular slide.
> Currently what we're doing is that we first read the slide once,
> skipping everything
> except clrMap. Then we read the slide again (yay!) and start the real
> conversion.
>
> There was something similar in xlsx filters too if my memory serves me
> correctly.
>
See also somewhat related XmlWriteBuffer in
filters/libmsooxml/MsooXmlUtils.h which is used "when information that
has to be written in advance is based on XML elements parsed later. In
such case the information cannot be saved in one pass" for OOXML=>ODF.
In the case of XSLT I also remember that there where a problem with
offset-references. Means something like (pseudo-xml):
<style>
<item>index 0</index>
<item>index 1</index>
<item>index 2</index>
</style>
<content>
<content withStyleIndex="1"> // where 1 references to the second
stlye-item
<content>
XSLT does iirc not allow such index-based reference-fetching making it
needed to for-loop with counter over the <style> items all the time they
are referenced. Super expensive and iirc not caching is done (my
knowledge there is a few years old, so maybe that changed). A classic
case where someone just likes to introduce a "caching concept" to read
all the items at once, prepare them and access them later on direct by
index from a style-container/mnager. OOXML makes quit a lot of use of
such index-based references being a 1:1 port from C/C++ to XML.
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<div class="moz-cite-prefix">On 03/26/2013 02:51 PM, Lassi Nieminen
wrote:<br>
</div>
<blockquote
cite="mid:CABCpZwrTLGFWnrfTF6NaTeJgKtRqAcc46OC6UmAqu3ktA+mHKA@mail.gmail.com"
type="cite">Hola,<br>
<br>
<div class="gmail_quote">On Mon, Mar 25, 2013 at 8:12 PM, Inge
Wallin <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:inge@lysator.liu.se" target="_blank">inge@lysator.liu.se</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">On Monday, March 25, 2013 17:54:53 <a
moz-do-not-send="true" href="mailto:matus.uzak@gmail.com">matus.uzak@gmail.com</a>
wrote:<br>
> Hi,<br>
><br>
> sorry for not discussing earlier, but I did not have
much free time last<br>
> two weeks.<br>
><br>
> I think we should continue the parser type discussion
in order to also<br>
> improve state of things in libmsooxml. What we have
there is a PULL<br>
> parser. And I identified the following problems (Would
be cool is Lassi<br>
> could check those):<br>
><br>
> 1. OOXML sometimes requires us to run the parser twice
at one element in<br>
> order to first collect selected information required to
convert the content<br>
> of child elements.<br>
><br>
> 2. There are situations when conversion of the 1st
child of the root<br>
> element requires information from the last child of the
root element.<br>
<br>
</div>
It would be interesting to see some examples of these two
issues.</blockquote>
<div><br>
</div>
<div>As an example : in pptx files, in slides,</div>
<div>there can be text which is specified to use theme color lt1</div>
<div><br>
</div>
<div>Don't remember the exact syntax, but something like</div>
<div><p></div>
<div><rPr "color" = "lt1"/></div>
<div><r>Hejsan</r></div>
<div></p></div>
<div>
<br>
</div>
<div>Then as the last element of that slide there may or may not
be</div>
<div><clrMap "lt1" = "bg1" ...../> // or something similar</div>
<div><br>
</div>
<div>Which means that lt1 should be interpreted to be bg1 for
this particular slide.</div>
<div>Currently what we're doing is that we first read the slide
once, skipping everything</div>
<div>except clrMap. Then we read the slide again (yay!) and
start the real conversion.</div>
<div><br>
</div>
<div>There was something similar in xlsx filters too if my
memory serves me correctly.</div>
<div><br>
</div>
</div>
</blockquote>
<br>
See also somewhat related XmlWriteBuffer in
filters/libmsooxml/MsooXmlUtils.h which is used "when information
that has to be written in advance is based on XML elements parsed
later. In such case the information cannot be saved in one pass"
for OOXML=>ODF.<br>
<br>
In the case of XSLT I also remember that there where a problem with
offset-references. Means something like (pseudo-xml):<br>
<br>
<style><br>
<item>index 0</index><br>
<item>index 1</index><br>
<item>index 2</index><br>
</style><br>
<br>
<content><br>
<content withStyleIndex="1"> // where 1 references to the
second stlye-item<br>
<content><br>
<br>
XSLT does iirc not allow such index-based reference-fetching making
it needed to for-loop with counter over the <style> items all
the time they are referenced. Super expensive and iirc not caching
is done (my knowledge there is a few years old, so maybe that
changed). A classic case where someone just likes to introduce a
"caching concept" to read all the items at once, prepare them and
access them later on direct by index from a style-container/mnager.
OOXML makes quit a lot of use of such index-based references being a
1:1 port from C/C++ to XML.<br>
<br>
</body>
</html>
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