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Unshare shape properties for the same type before insertion in Impress

Estimated read time: 2 minutes

Shape properties were shared by shape type (e.g. shared between group shapes) before insertion into a document model in Impress. This is now fixed: the property names and types are still shared to help performance, but their values are no longer shared. This helps matching the user expectation that separate opened documents don’t share information with each other.

First, thanks to our partner SUSE for working with Collabora to make this possible.


I was working on a testcase for tdf#132696 when I noticed that the existing CppunitTest_oox_drawingml testsuite runs fine before my changes, also a newly added testGroupShapeSmartArt testcase runs fine in isolation, but if I run the whole testsuite, then it breaks.

Further investigation revealed that in case testGroupShapeSmartArt is executed first, then testTdf131082 fails. This means:

  • the first document is opened

  • the first document is closed

  • the second document is opened

  • the second document is saved

And at this point information from the first document is leaked to the second document, even if the first document was already closed by the time we performed the save. It turns out the root cause was i#114206 (reported in 2010), i.e. group shapes shared their property values till they got inserted to the document model. The first document import did not consume pending SmartArt properties on a to-be-inserted group shape, the second import was looking for pending properties, found them. And then the second document’s save wrote those pending properties to the file, leading to this unexpected leak.

Here is how the first document looks like, containing the blue rectangles (a SmartArt):
Figure 1. First document with a SmartArt

Here is how the second document looks like, without a SmartArt:
Figure 2. Second document after loading, no SmartArt

And here is how the second document looks, after saving to PPTX and reloading:
Figure 3. Second document after reloading, with a SmartArt

Results so far

The fix is to split out part of SvxItemPropertySet to a separate class, so that we can keep sharing SvxItemPropertySet between multiple instances of the same shape type (describing the name and type of the various properties), while introducing a new SvxItemPropertySetUsrAnys that is specific to each not-yet-inserted shape. This way each pending shape is independent, and in case they are not inserted to the document model later, that results in no side-effects.

Want to start using this?

Collabora intends to continue supporting and contributing to LibreOffice, the code is merged so we expect all of this work will be available in TDF’s next release (7.3).

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