InteropGrabBag in LibreOffice Writer

FOSDEM 2014 (https://fosdem.org/2014/schedule/event/interopgrabbag_in_libreoffice_writer/), Brussels

Transcript

1. InteropGrabBag in LibreOffice Writer Miklos Vajna 2014­02­01
2. Filter problems
3. 3 / 15 FOSDEM 2014 | Miklos Vajna What is a filter problem? • Filters map between an input/output stream and the document model • A given filter: given file format • If a feature in a file format is not roundtripped perfectly through the document model
4. 4 / 15 FOSDEM 2014 | Miklos Vajna Case #0: feature is already in core • RTF import, groupshape support
5. 5 / 15 FOSDEM 2014 | Miklos Vajna Case #1: Implement the feature in core
6. 6 / 15 FOSDEM 2014 | Miklos Vajna Case #2: Import the result of the feature in the filter • E.g. Table styles, document themes • SmartArt import • On import, apply the result of that as direct formatting • Better, than nothing, but no real editing can be performed
7. InteropGrabBag
8. 8 / 15 FOSDEM 2014 | Miklos Vajna Case #3: Just preserve it • If a feature is completely unsupported by core, it makes sense to first just preserve it • Use case: • Long document • Full of complicated features • Just want to correct a typo
9. 9 / 15 FOSDEM 2014 | Miklos Vajna We do it for ODF already • css::xml::ParaUserDefinedAttributesSupplier • css::xml::TextUserDefinedAttributesSupplier • css::xml::UserDefinedAttributesSupplier • “The idea behind this property is that a parser can throw away all attributes that it cannot handle by itself […] can be written back without loss.” • WW8 as well: SwTOXBase::maMSTOCExpression
10. 10 / 15 FOSDEM 2014 | Miklos Vajna Why a new API? • Need separate storage • ODF foreign format → – Would need manual mapping anyway • Need a more flexible data structure • UserDefinedAttributes is just a string­string map • We want to store nested structures as well
11. 11 / 15 FOSDEM 2014 | Miklos Vajna The InteropGrabBag API • New SfxPoolItem: SfxGrabBagItem • Writer: RES_{CHR,PAR}ATR_GRABBAG, etc. • UNO: InteropGrabBag property • Type: css::beans::PropertyValues – Effectively a string­any map
12. 12 / 15 FOSDEM 2014 | Miklos Vajna A set of bags • Each UNO object may implement it, currently supported: • css::document::OfficeDocument • css::drawing::Shape • css::style::CharacterProperties • css::style::ParagraphProperties • css::style::Style • css::text::BaseFrameProperties
13. 13 / 15 FOSDEM 2014 | Miklos Vajna The danger of hidden properties • Problem: e.g. paragraph border is not supported, hidden “big black border” property • User copy&pastes it elsewhere • Result: pasted paragraph still has that property, probably not wanted • Solution: clear InteropGrabBag on copying / when object is altered
14. 14 / 15 FOSDEM 2014 | Miklos Vajna Just for Writer? • The API is generic to be used in Calc, Impress, etc. • Currently mostly implemented for Writer only • Just for OOXML? • It's the only user ATM • Different properties can happy co­exist – Most of current keys are prefixed with OOX anyway
15. 15 / 15 FOSDEM 2014 | Miklos Vajna Conclusions • The end result: much improved OOXML roundtrip • Now perfect roundtrip examples (incomplete list): • Document themes • SmartArt • Table styles