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.

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