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List: calligra-devel
Subject: Re: a new library for traversing odf files and a new export filter
From: matus.uzak () gmail ! com
Date: 2013-03-26 11:07:06
Message-ID: CAMt8kKXyUhBWEvf18MOtb8VFpa2kYqK5hfUsGt3YFOe=f0P5dw () mail ! gmail ! com
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>
> 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.
>
The worst thing is relative line-height and font-size. It must be mapped
into absolute values because each filter uses specific equations which were
reverse engineered. Most of these equations include the max/min pair. So
we first have to parse paragraph content to calculate it's
line-height/font-size and then updated text styles.
But I think this does not interfere with the Pull parser concept. We
simply do some action on styles when coming out of the recursion
(backtracking).
On Tue, Mar 26, 2013 at 10:32 AM, Sebastian Sauer <mail@dipe.org> wrote:
> 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> wrote:
>
>> On Monday, March 25, 2013 17:54:53 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.
>
>
> _______________________________________________
> calligra-devel mailing list
> calligra-devel@kde.org
> https://mail.kde.org/mailman/listinfo/calligra-devel
>
>
[Attachment #5 (text/html)]
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc \
solid;padding-left:1ex">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> \
</blockquote><div><br></div><div>The worst thing is relative line-height and \
font-size. It must be mapped into absolute values because each filter uses specific \
equations which were reverse engineered. Most of these equations include the max/min \
pair. So we first have to parse paragraph content to calculate it's \
line-height/font-size and then updated text styles.</div> <div><br></div><div>But I \
think this does not interfere with the Pull parser concept. We simply do some action \
on styles when coming out of the recursion (backtracking).</div><br><div \
class="gmail_quote">On Tue, Mar 26, 2013 at 10:32 AM, Sebastian Sauer <span \
dir="ltr"><<a href="mailto:mail@dipe.org" \
target="_blank">mail@dipe.org</a>></span> wrote:<br> <blockquote \
class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc \
solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"><div><div class="h5">
<div>On 03/26/2013 02:51 PM, Lassi Nieminen
wrote:<br>
</div>
<blockquote type="cite">Hola,<br>
<br>
<div class="gmail_quote">On Mon, Mar 25, 2013 at 8:12 PM, Inge
Wallin <span dir="ltr"><<a 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>On Monday, March 25, 2013 17:54:53 <a \
href="mailto:matus.uzak@gmail.com" target="_blank">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></div></div>
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>
</div>
<br>_______________________________________________<br>
calligra-devel mailing list<br>
<a href="mailto:calligra-devel@kde.org">calligra-devel@kde.org</a><br>
<a href="https://mail.kde.org/mailman/listinfo/calligra-devel" \
target="_blank">https://mail.kde.org/mailman/listinfo/calligra-devel</a><br> \
<br></blockquote></div><br>
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