Relax TextPFRun validation to allow LibreOffice PPT import
Summary:
This change allows non-conforming LibreOffice PPT files to be imported.
An apparent bug in the LibreOffice PPT exporter makes it output files
which technically don't conform to the PPT specification. Calligra
refuses to load these files, which although technically may be the
correct behaviour, is extremely annoying for the user. LibreOffice's
deviation from the PPT spec is pretty minor, and a slight weakening of
Calligra's validation allows the files to be imported successfully.
In more detail, when loading a drawing each text paragraph in the
drawing has a TextPFRun structure ("A structure that specifies the
paragraph-level formatting of a run of text"). This starts with a mask,
followed by a sequence of fields. Only unmasked fields are included in
the sequence.
According to Section 2.9.45 of the PPT specification version 6 [1], the
following fields must be masked out:
masks.leftMargin
masks.indent
masks.defaultTabSize
masks.tabStops
In spite of this LibreOffice includes the leftMargin and indent fields
(flags 0x100 and 0x400). I'm not familiar with the LibreOffice codebase,
but it looks like this is the problem code. From this same code it look
like LibreOffice doesn't export the defaultTabSize or tabStops fields
(which is correct).
This patch loosens Calligra's validation to allow these flags to be set.
It applies the change in binschema [2] for the same reason used to
generate the Calligra parser files (see binschma commit
aca4fd06f1ad330ecadf05b9e862d7c91338f051).
[1] https://docs.microsoft.com/en-us/openspecs/office_file_formats/ms-ppt
[2] https://phabricator.kde.org/source/binschema/
Test Plan:
- Save out a file from LibreOffice in PPT format, or download this archive with a test file inside.
- Attempt to load the file into Calligra Stage.
- Note that it refuses to load with the error "Invalid file format".
- Apply the patch.
- Attempt to load the same file again.
- Note that it loads correctly. If you used my test file, witness my amazing presentation design.
Reviewers: pvuorela, dcaliste
Reviewed By: pvuorela
Subscribers: Calligra-Devel-list, davidllewellynjones
Tags: #calligra:_3.0
Differential Revision: https://phabricator.kde.org/D25256