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47 lines
2.9 KiB
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47 lines
2.9 KiB
Markdown
<!-- Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license. -->
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# File View Providers
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<link-summary>Handling multiple languages PSI trees in a single file.</link-summary>
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A file view provider ([`FileViewProvider`](%gh-ic%/platform/core-api/src/com/intellij/psi/FileViewProvider.java)) manages access to multiple PSI trees within a single file.
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For example, a JSPX page has a separate PSI tree for the Java code in it (`PsiJavaFile`), a separate tree for the XML code (`XmlFile`), and a separate tree for JSP as a whole ([`JspFile`](%gh-ic%/java/jsp-openapi/src/com/intellij/psi/jsp/JspFile.java)).
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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.
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A `FileViewProvider` instance corresponds to a single `VirtualFile`, a single `Document`, and can retrieve multiple `PsiFile` instances.
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## How do I get a `FileViewProvider`?
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| Context | API |
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|---------------------------------|------------------------------------------------------------------------------------------------------------------------|
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| [PSI File](psi_files.md) | [`PsiFile.getViewProvider()`](%gh-ic%/platform/core-api/src/com/intellij/psi/PsiFile.java) |
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| [Virtual File](virtual_file.md) | [`PsiManager.getInstance(project).findViewProvider()`](%gh-ic%/platform/core-api/src/com/intellij/psi/PsiManager.java) |
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## What can I do with a `FileViewProvider`?
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* To get the set of all languages for which PSI trees exist in a file: `fileViewProvider.getLanguages()`
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* To get the PSI tree for a particular language: `fileViewProvider.getPsi(language)`.
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For example, to get the PSI tree for XML, use `fileViewProvider.getPsi(XMLLanguage.INSTANCE)`.
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* To find an element of a particular language at the specified offset in the file: `fileViewProvider.findElementAt(offset, language)`
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## How do I extend the `FileViewProvider`?
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To create a file type that has multiple interspersing trees for different languages, a plugin must contain an extension to
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the <include from="snippets.topic" element-id="ep"><var name="ep" value="com.intellij.fileType.fileViewProviderFactory"/></include>.
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Implement [`FileViewProviderFactory`](%gh-ic%/platform/core-api/src/com/intellij/psi/FileViewProviderFactory.java) and return your `FileViewProvider` implementation from `createFileViewProvider()` method.
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Register as follows in <path>[plugin.xml](plugin_configuration_file.md)</path>:
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```xml
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<extensions defaultExtensionNs="com.intellij">
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<fileType.fileViewProviderFactory
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filetype="$FILE_TYPE$"
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implementationClass="com.example.MyFileViewProviderFactory"/>
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</extensions>
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```
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Where `$FILE_TYPE$` refers to the type of the file being created (for example, "JSF").
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