Idea Plugin Dev - Documents

1 - About

A document is an editable sequence of Unicode characters, which typically corresponds to the text contents of a virtual file.

3 - Structure

Line breaks in a document are always normalized to \n.

The IntelliJ Platform handles encoding and line break conversions when loading and saving documents transparently.

4 - Management

4.1 - Instantiation / Creation

Document instances are created:

  • when some operation needs to access the text contents of a file (in particular, this is needed to build the PSI for a file).
  • when document instances are not linked to any virtual files. They are then created temporarily, for example, to represent the contents of a text editor field in a dialog.

Normally, you don't create a document as it's bounded (to a PSI file, virtual file, …). See get section.

To create a document, you can create a PSI file and then get its Document.

If you still need to create a Document instance which isn’t bound to anything, you can use EditorFactory.createDocument

4.2 - Get

  • From an action: e.getData(PlatformDataKeys.EDITOR).getDocument()
  • From a virtual file: FileDocumentManager.getDocument(). This call forces the document content to be loaded from disk if it wasn’t loaded previously; if you’re only interested in open documents or documents which may have been modified, use FileDocumentManager.getCachedDocument() instead.
  • From a PSI file: PsiDocumentManager.getInstance().getDocument() or PsiDocumentManager.getInstance().getCachedDocument()

4.3 - Operations

You may perform any operations that access or modify the file contents on “plain text” level (as a sequence of characters, not as a tree of Java elements).

The general read/write action rules are in effect.

Any operations which modify the contents of the document must be wrapped in a command (CommandProcessor.getInstance().executeCommand()).

  • executeCommand() calls can be nested,
  • The outermost executeCommand call is added to the undo stack.

If multiple documents are modified within a command, undoing this command will by default show a confirmation dialog to the user.

If the file corresponding to a Document is read-only (for example, not checked out from the version control system), document modifications will fail. Thus, before modifying the Document, it is necessary to call ReadonlyStatusHandler.getInstance(project).ensureFilesWritable() to check out the file if necessary.

All text strings passed to Document modification methods (setText, insertString, replaceString) must use only \n as line separators.

4.4 - Persistence

Document instances are weakly referenced from VirtualFile instances. Thus, an unmodified Document instance can be garbage-collected if it isn’t referenced by anyone, and a new instance will be created if the document contents is accessed again later. Storing Document references in long-term data structures of your plugin will cause memory leaks.

4.5 - Watcher / Notification

Method allows to receive notifications ..
Document.addDocumentListener about changes in a particular Document instance
EditorFactory.getEventMulticaster().addDocumentListener about changes in all open documents.
FileDocumentManager.addFileDocumentManagerListener when any Document is saved or reloaded from disk.

4.6 - Scope

A document has an application scope (even if multiple projects are open, each file is represented by the same VirtualFile instance).


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