AW: [xep-support] text positioning differences between XEP 3.6.3 and 3.7.x

From: uwe.goersch@LHSYSTEMS.COM
Date: Wed Mar 24 2004 - 05:53:32 PST

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    Dear Benoit,

    I think there is a difference between changes to the content (maybe you have some layout indepent XML document which is converted to an FO XML document to hold this information), changes to the layout (which you may define in an XSLT transformation) which reflects in the FO document as well and changes to page formatting (changes in XEP) which reflect in the intermediate, propreitary XML document you call AT as well as the others.

    Since this XML document reflects content, layout and formatting changes, a byte-by-byte comparison of the "AT" files seems potentially dangerous to me and will not be supported by RenderX. If you want to use these files still for the comparison, you may try to strip some layout and formatting information from the files before you compare them (a SAX parser step). Still dangerous but maybe somewhat more stable. At least you should not rely on absolute positions measured in 0,001pt (1/72,000inch)!

    If you can, you may compare the input as early as possible. Maybe - depending on your business nd implementation scenario - on the level of the layout independent XML document. You may than insert some revision markup (empty XML elements) to mark start and end of a change to the content and "route it through" to the "AT" document (using rx:pinpoint) to highlight the changes. Still if you need to find out pages which have changed (for example in a loose-leaf collection scenario) this is not sufficient, since unchanged content may "shift" over pages with changes to other content pages before (as for insertions and deletions).

    Kind regards

    Uwe

    -----Ursprüngliche Nachricht-----
    Von: owner-xep-support@renderx.com
    [mailto:owner-xep-support@renderx.com]Im Auftrag von MAISONNY Benoit
    Gesendet: Mittwoch, 24. März 2004 13:20
    An: Xep-Support (E-mail)
    Betreff: [xep-support] text positioning differences between XEP 3.6.3
    and 3.7.x

    Hi,

    We compared the AT files produced from the same FO file using different versions of XEP, and found differences in the positioning and width of elements. For example:

    xep363: <xep:text value="Copyright " x="332218" y="46987" width="36456"/>
    xep372: <xep:text value="Copyright " x="332386" y="46989" width="36440"/>

    In some cases, the differences in "y" value can amount to 10000. The difference in width is probably the cause of the positioning differences. Perhaps you changed the algorithm to compute the characters' size?

    Of course, we are using the same fonts.xml file, on the same computer, to compare results.

    Is there a way to avoid these differences? We need to find which pages have changed between 2 versions of a document, and we are using the AT format to spot any difference. But in this case, the differences on the page are due to XEP, not to any change in content.

    Thanks,
    Benoit Maisonny

    ......................................................................
    Benoit MAISONNY benoit.maisonny@eurocontrol.int
    eAIP development & support http://www.eurocontrol.int/ais/eaip
    EUROCONTROL Aeronautical Information Management

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