LibreOffice » extensions
This module contains a grab-bag of unrelated misc. libraries, *none* of which is an extension.
When we start LO, first InitUpdateCheckJobThread is created, via UpdateCheckJob::execute() (from extensions/source/update/check/updatecheckjob.cxx), as a reaction to a "onFirstVisibleTask" event. It waits 25 seconds (so that it does not interfere with the startup itself), and then calls UpdateCheck::initialize() (from extensions/source/update/check/updatecheck.cxx).
This creates one more thread, UpdateCheckThread, that regularly checks whether we have reached the time when we should ask for the update. If yes, asks for that, and shows the download button in the menu (if the new update is available).
A bridge between "OLE automation" and UNO, so you can use UNO services from JScript, VBScript, etc.
This is initialized in Desktop::Main() in Desktop::OpenClients_Impl() by creating the service "com.sun.star.bridge.OleApplicationRegistration", which is implemented by OleServer_Impl.
This allows embedding LO into a Win32 application as an ActiveX control. See extensions/source/activex/
On macOS, this allows indexing ODF documents with Spotlight. See extensions/source/macosx/spotlight/
You can scan from LibreOffice, using platform specific backends like TWAIN/SANE. See extensions/source/scanner/