Steps to reproduce:
1. Open a large project folder, my example contains hundreds of files spread out amongst tens of folders.
2. Open a file within that project, my example was a subclass of a base Controller. (BaseController.php > ExtendedController.php, opening 'ExtendedController.php')
3. After opening, I immediately noticed a percentage ticker in the status bar on the bottom of the window. Hovering over the number revealed that it was the indexed percentage.
4. Close the document.
The number stopped incrementing after I closed the document. Reopening the document did not restart the indexing process. Opening a different document did not restart the process. In fact, I wasnt able to restart the project indexing process even after exiting ST3 and restarting it.
I believe the project indexer should be a separate, disconnected process from the opened document. It should not fail when the document is closed. It would also be nice to have some control over the process. The ability to start and stop the process from the File menu would be ideal, and extra credit would be the ability to index only selected sub folders.