@Override
  public void documentChanged(DocumentEvent event) {
    if (myStopTrackingDocuments) return;

    final Document document = event.getDocument();
    VirtualFile virtualFile = FileDocumentManager.getInstance().getFile(document);
    boolean isRelevant = virtualFile != null && isRelevant(virtualFile);

    final FileViewProvider viewProvider = getCachedViewProvider(document);
    if (viewProvider == null) {
      handleCommitWithoutPsi(document);
      return;
    }
    boolean inMyProject = viewProvider.getManager() == myPsiManager;
    if (!isRelevant || !inMyProject) {
      myLastCommittedTexts.remove(document);
      return;
    }

    ApplicationManager.getApplication().assertWriteAccessAllowed();
    final List<PsiFile> files = viewProvider.getAllFiles();
    boolean commitNecessary = true;
    for (PsiFile file : files) {

      if (mySynchronizer.isInsideAtomicChange(file)) {
        commitNecessary = false;
        continue;
      }

      assert file instanceof PsiFileImpl
              || "mock.file".equals(file.getName())
                  && ApplicationManager.getApplication().isUnitTestMode()
          : event + "; file=" + file + "; allFiles=" + files + "; viewProvider=" + viewProvider;
    }

    boolean forceCommit =
        ApplicationManager.getApplication().hasWriteAction(ExternalChangeAction.class)
            && (SystemProperties.getBooleanProperty("idea.force.commit.on.external.change", false)
                || ApplicationManager.getApplication().isHeadlessEnvironment()
                    && !ApplicationManager.getApplication().isUnitTestMode());

    // Consider that it's worth to perform complete re-parse instead of merge if the whole document
    // text is replaced and
    // current document lines number is roughly above 5000. This makes sense in situations when
    // external change is performed
    // for the huge file (that causes the whole document to be reloaded and 'merge' way takes a
    // while to complete).
    if (event.isWholeTextReplaced() && document.getTextLength() > 100000) {
      document.putUserData(BlockSupport.DO_NOT_REPARSE_INCREMENTALLY, Boolean.TRUE);
    }

    if (commitNecessary) {
      assert !(document instanceof DocumentWindow);
      myUncommittedDocuments.add(document);
      myDocumentCommitProcessor.log(
          "added uncommitted doc",
          null,
          false,
          myProject,
          document,
          ((DocumentEx) document).isInBulkUpdate());
      if (forceCommit) {
        commitDocument(document);
      } else if (!((DocumentEx) document).isInBulkUpdate() && myPerformBackgroundCommit) {
        myDocumentCommitProcessor.commitAsynchronously(myProject, document, event);
      }
    } else {
      myLastCommittedTexts.remove(document);
    }
  }