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Plugin System

Summary

OmegaT's plugin architecture allows extending functionality through .jar files that register new filters, machine translators, glossaries, tokenizers, markers, and base functionality — without modifying the core codebase.

How Plugins Work

A plugin is a single .jar file placed in the /plugins/ directory (user-level: ~/.omegat/plugins/ or system-level). If a plugin needs additional libraries, they are placed in the same directory.

Plugin Manifest

Since OmegaT 3.0.1+, a plugin declares its initialization class in the manifest:

Plugin-Name: My Plugin Plugin-Version: 1.0.0 Plugin-Author: Developer Name Plugin-Description: What this plugin does OmegaT-Plugins: com.example.MyPluginInit

The initialization class must have: java public static void loadPlugins() // Called at startup, before GUI init public static void unloadPlugins() // Called at shutdown

Plugin Types

Type Purpose Registration
filter Parse/build translation files in new formats Core.registerFilterClass()
tokenizer Split segments into tokens for spell checking/matching Core.registerTokenizerClass()
marker Visual markers in the editor (e.g., highlighting) Core.registerMarkerClass()
machinetranslator Integrate MT engines (Google, DeepL, Azure) Core.registerMachineTranslatorClass()
glossary Provide glossary/terminology results Core.registerGlossaryClass()
base General-purpose plugins without specific type Standard registration

Plugin Loading Lifecycle

  1. Startup — loadPlugins() runs before any GUI initialization
  2. Registration — Plugin registers its classes (filters, markers, etc.)
  3. Version check — Plugin should verify OmegaT compatibility
  4. Error handling — If incompatible, Core.pluginLoadingError() shows message after GUI init
  5. Shutdown — unloadPlugins() runs on application exit (usually empty)

Best Practices

  • Separate initialization from implementation — The init class should only use Core and CoreEvents to catch loading errors gracefully
  • Don't execute long operations in loadPlugins() — It blocks startup
  • Check version compatibility — Use try/catch to handle API changes between OmegaT versions
  • FatJar packaging — Bundle all runtime dependencies into a single jar

Extension Points (Post-GUI)

Additional extension points available after GUI initialization via IApplicationEventListener.onApplicationStartup():

  • IGlossary — Custom glossary providers via Core.getGlossaryManager().addGlossaryProvider()
  • IDictionaryFactory / IDictionary — Custom dictionary formats via Core.getDictionaries().addDictionaryFactory()
  • AbstractAutoCompleterView — Custom auto-completion UIs via Core.getEditor().getAutoCompleter().addView()

Plugin Development

OmegaT provides: - plugin-skeleton — Gradle-based plugin development starter with Groovy and Kotlin DSL examples - gradle-omegat-plugin — Custom Gradle plugin handling OmegaT core references - FatJar generation — PackIntoJar configuration bundles dependencies automatically - CI/CD — GitHub Actions example for automated plugin builds

Notable Plugins

  • DeepL Connector — DeepL V2 API integration
  • Azure Translate — Microsoft Azure Translate V3
  • Certified plugins database — Community-maintained collection at omegat-plugins (Kotlin)

See Also