A file view provider (see the FileViewProvider class) manage access to multiple PSI trees within a single file.
For example, a JSPX page has:
A FileViewProvider instance corresponds to:
Each of the PSI trees covers the entire contents of the file, and contains special “outer language elements” in the places where contents in a different language can be found.
To create a file type that has multiple interspersing trees for different languages, your plugin must contain an extension to the fileType.fileViewProviderFactory extension point available in the IntelliJ Platform core.
This extension point is declared using the FileTypeExtensionPoint bean class.
To access this extension point, create a Java class that implements the FileViewProviderFactory interface, and in this class, override the createFileViewProvider method.
To declare the extension to the fileType.fileViewProviderFactory extension point, to the
section of the plugin.xml file, add the following syntax:
<fileType.fileViewProviderFactory filetype=“%file_type%” implementationClass=“%class_name%” />
Where %file_type% refers to the type of the file being created (for example, “JFS”), and the %class_name% refers to the name of your Java class that implements the FileViewProviderFactory interface.
===== Documentation / Reference =====
* http://www.jetbrains.org/intellij/sdk/docs/basics/architectural_overview/file_view_providers.html