The purpose of the document is to describe steps necessary to create localized versions of IDEA.
Application Bundle Layout
In regard to localization purpose all the resources (in English) that need to be translated are located in jar files called resources_en.jar. There's one such jar file for IDEA core functionality located at INSTALL_HOME\lib\resources_en.jar and one jar for each of bundled plugins at INSTALL_HOME\plugins$Plugin$\lib\resources_en.jar.
Translated resources should be jarred and placed exactly in the same folder original jar comes from. So localization pack should have exactly the same number of jar files, and they have to be laid out in exactly the same way original jars are laid out. In order to enable multiple localizations per installation without localization packs overriding each other we suggest to include the name of the locale in the jar name (for example, resources_ja.jar).
Content and Layout of resources_en.jar
Property files usually contain messages, menu items, dialog labels texts etc. For every such file localized jar should contain translated version that is placed to exactly the same path relative to the jar root and has exactly the same name as original file plus locale identifier. For example messages/ActionsBundle.properties file from resources_en.jar should have its translated version messages/ActionsBundle_ja.properties file in resources_ja.jar. All property files should be ASCII encoded with \uXXXX sequences used for characters that have no representation in ASCII range. See native2ascii tool for more details.
Property values mostly follow MessageFormat rules.
Inspection descriptions appear in Settings|Errors and represent short information about what each of the inspection tools is intended to do. Each description is represented by single html file under /inspectionDescriptions/ folder that should be encoded in UTF-8 encoding. Localized versions should be stored in folder suffixed with locale instead. For instance /inspectionDescriptions/CanBeFinal.html from resources_en.jar translation should be placed in /inspectionDescriptions_ja/CanBeFinal.html in resources_ja.jar.
Intention descriptions and samples are very similar to inspection descriptions but the layout is a bit more advanced. Every intention has a bunch of files located in the folder named after intention's short name in /intentionDescriptions/. These files include description.html, which holds description similar to inspection one plus a couple of template files demonstrating what the intention will do on a sample. Those templates are optional to translate. Similar to inspection descriptions whole intentionDescriptions folder should be suffixed with locale identifier. For instance /intentionDescriptions/AddOnDemandStaticImportAction/description.html translation should be placed in /intentionDescriptions_ja/AddOnDemandStaticImportAction/description.html. All the HTML files should be UTF-8 encoded.
Tips of the day follow the same pattern inspections and intentions do. For instance translation of /tips/AdaptiveWelcome.html goes to /tips_ja/AdaptiveWelcome.html. The only thing special about tips is they use special pattern for denoting shortcuts like EnterAction; will be replaced to keystroke mapped to EnterAction in currently used keymap at run-time. So please make sure you leave such sequences intact while translating. Remember UTF-8 encoding.
File templates again go the same way (if at all should be translated). /fileTemplates/Singleton.java.ft goes to /fileTemplates_ja/Singleton.java.ft.
Following Sun rules for property bundles whenever certain resource cannot be found in localized version its default version from resources_en.jar will be used instead.