private boolean isApplicableEditor(TextEditor textEditor) {
    final Document document = textEditor.getEditor().getDocument();
    final PsiFile psiFile = PsiDocumentManager.getInstance(myProject).getPsiFile(document);

    // In theory, we should just check
    //   LayoutDomFileDescription.isLayoutFile((XmlFile)psiFile);
    // here, but there are problems where files don't show up with layout preview
    // at startup, presumably because the resource directories haven't been properly
    // initialized yet.
    return isInResourceFolder(psiFile);
  }
 @Override
 @NotNull
 public Editor getEditor() {
   final TextEditor fileEditor = myPanel.getFileEditor();
   if (fileEditor != null) {
     return fileEditor.getEditor();
   }
   if (myMockTextEditor == null) {
     myMockTextEditor = EditorFactory.getInstance().createViewer(new DocumentImpl(""), myProject);
   }
   return myMockTextEditor;
 }