LibreOffice version 4.0 came out today, with project organizers boasting a "cleaner and leaner code base" along with various new features and greater interoperability with business systems and document formats.

LibreOffice was launched in 2010 to overtake OpenOffice as the preeminent open source office suite. Google Docs may still be the biggest threat to Microsoft Office, but LibreOffice has carved out a niche for itself, becoming the default productivity software on many popular Linux distributions.

Cleaning up the code has been a major focus. "The resulting code base is rather different from the original one, as several million lines of code have been added and removed, by adding new features, solving bugs and regressions, adopting state of the art C++ constructs, replacing tools, getting rid of deprecated methods and obsoleted libraries, and translating twenty-five thousand lines of comments from German to English," the Document Foundation said in its LibreOffice 4.0 announcement. "All of this makes the code easier to understand and more rewarding to be involved with for the stream of new members of our community."

Better interoperability wtih DOCX and RTF documents is in LibreOffice 4.0, as is integration with numerous content and document management systems. There is also a new Android app for controlling presentations. There is an Android port of LibreOffice in the works, but there wasn't any update on that project today.

Here's a more complete list of new features, courtesy of the Document Foundation:

Integration with several content and document management systems - including Alfresco, IBM FileNet P8, Microsoft Sharepoint 2010, Nuxeo, OpenText, SAP NetWeaver Cloud Service and others - through the CMIS standard.

Better interoperability with DOCX and RTF documents, thanks to several new features and improvements like the possibility of importing ink annotations and attaching comments to text ranges.

Possibility to import Microsoft Publisher documents, and further improvement of Visio import filters with the addition of 2013 version (just announced).

Additional UI incremental improvements, including Unity integration and support of Firefox Themes (Personas) to give LibreOffice a personalized look.

Introduction of the widget layout technique for dialog windows, which makes it easier to translate, resize and hide UI elements, reduces code complexity, and lays a foundation for a much improved user interface.

Different header and footer on the first page of a Writer document, without the need of a separate page style.

Several performance improvements to Calc, plus new features such as export of charts as images (JPG and PNG) and new spreadsheet functions as defined in ODF OpenFormula.

First release of Impress Remote Control App for Android, supported only on some Linux distributions. (The second release, coming soon, will be supported on all platforms: Windows, MacOS X and all Linux distros and binaries.)

Significant performance improvements when loading and saving many types of documents, with particular improvements for large ODS and XLSX spreadsheets and RTF files.

Improved code contribution thanks to Gerrit: a web-based code review system, facilitating the task for projects using Git version control system (although this is not specific of LibreOffice 4.0, it has entered the production stage just before the 4.0 branch).

There are also a number of API changes that might be of interest to developers. LibreOffice itself can be downloaded at the project's home page.