Writing Import filters for “beginners”

Transcript

1. Writing Import filters for “beginners” Ha, ha, ha, I got you!!! Fridrich Štrba Software Engineer & TrainedMonkey™ LibreOffice Team Novell, Inc.
2. © Novell, Inc. All rights reserved. 2 Agenda • Why would anybody care about writing import filters? • What interfaces are available for filter developers • Technicalities that will make you feel cool if I manage to explain them (after I actually understand them myself)
3. Why import filters ?
4. © Novell, Inc. All rights reserved. 4 Legacy formats out there • ODF is the future of the humanity – Nevertheless, humanity does not know about it as of now • Other de facto standards – Some people use other Office Suites :( • Hard-disks full of teenage poetry in funny formats – LibreOffice offers the freedom to read that crap
5. © Novell, Inc. All rights reserved. 5 Pure intellectual exercise • Allows to program for LibreOffice without having to understand the internals thereof – Pretty stand-alone functionality communicating with LibreOffice over well defined interfaces … – … almost • Happy users will reward you – You will be the hero of the people who can now read their documents... – … and they will get on your nerves listing features that are not converted.
6. XSLT filters
7. © Novell, Inc. All rights reserved. 7 XSLT filters • The easiest way to write an import filter from other xml format – Possibility to add using user interface … – … and export as an extension • Used services – com.sun.star.comp.Writer.XMLOasisImporter > XSLT filter that pushes to LibreOffice flat ODT – com.sun.star.comp.Calc.XMLOasisExporter > XSLT filter that receives from LibreOffice flat ODS • Now it is even fast – Someone rewrote it from Java to C++
8. © Novell, Inc. All rights reserved. 8 New XSLT filter programming 1
9. © Novell, Inc. All rights reserved. 9 New XSLT filter programming 2
10. © Novell, Inc. All rights reserved. 10 New XSLT filter programming 3
11. © Novell, Inc. All rights reserved. 11 Filter description <node oor:name="OpenDocument Text Flat XML" oor:op="replace"> <prop oor:name="FileFormatVersion"> <value>0</value> </prop> <prop oor:name="Type"> <value>writer_ODT_FlatXML</value> </prop> <prop oor:name="DocumentService"> <value>com.sun.star.text.TextDocument</value> </prop> <prop oor:name="UIComponent" /> <prop oor:name="UserData"> <value oor:separator=","> com.sun.star.documentconversion.XSLTFilter,, com.sun.star.comp.Writer.XMLOasisImporter,com.sun.star.comp.Writer.XMLOasisExporter, ../share/xslt/odfflatxml/odfflatxmlimport.xsl, ../share/xslt/odfflatxml/odfflatxmlexport.xsl </value> </prop> <prop oor:name="FilterService"> <value>com.sun.star.comp.Writer.XmlFilterAdaptor</value> </prop> <prop oor:name="TemplateName" /> <prop oor:name="UIName"> <value>OpenDocument Text (Flat XML)</value> </prop> <prop oor:name="Flags"> <value>IMPORT EXPORT OWN 3RDPARTYFILTER</value> </prop> </node>
12. © Novell, Inc. All rights reserved. 12 Type description <node oor:name="writer_ODT_FlatXML" oor:op="replace"> <prop oor:name="DetectService"> <value>com.sun.star.comp.filters.XMLFilterDetect</value> </prop> <prop oor:name="URLPattern" /> <prop oor:name="Extensions"> <value>fodt odt xml</value> </prop> <prop oor:name="MediaType" /> <prop oor:name="Preferred"> <value>false</value> </prop> <prop oor:name="PreferredFilter"> <value>OpenDocument Text Flat XML</value> </prop> <prop oor:name="UIName"> <value>OpenDocument Text (Flat XML)</value> </prop> <prop oor:name="ClipboardFormat"> <value> doctype:office:mimetype="application/vnd.oasis.opendocument.text"</value> </prop> </node>
13. XFilter framework
14. © Novell, Inc. All rights reserved. 14 XFilter framework (XImporter, XExporter)
15. © Novell, Inc. All rights reserved. 15 Interfaces • com.sun.star.document.ImportFilter – XImporter > setTargetDocument – XFilter > filter > cancel – Win32 API and C runtime headers and import libraries • com.sun.star.document.ExportFilter – XExporter > SetSourceDocument – XFilter
16. © Novell, Inc. All rights reserved. 16 Document representation • com::sun::star::xml::sax::XDocumentHandler – startDocument – endDocument – startElement – endElement – characters – ignorableWhitespace – processingInstruction – setDocumentLocator
17. © Novell, Inc. All rights reserved. 17 File information • com::sun::star::document::MediaDescriptor – Represented by ::com::sun::star::beans::PropertyValue > Basically XML-ish structure with property names and their values – com::sun::star::io::XOutputStream OutputStream > A stream to receive the document data (for export filters) – com::sun::star::io::XInputStream InputStream > Content of document – string URL > URL of the document » Create the stream if it does not exist » Not necessary now because the XOutputStream or XinputStream are guaranteed
18. © Novell, Inc. All rights reserved. 18 Type detection • com::sun::star::document::XExtendedFilterDetection – string detect( sequence< ::com::sun::star::beans::PropertyValue > Descriptor) – Returns > any valid type name (which specifies the detected format) or an empty value for unknown formats. > Adds the information into the Descriptor
19. Q&A and Stoning session
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