Loading localized strings at runtime

Understand the rules for using localized strings at runtime.

Distributing compiled string files

The compiled string files (.42s) must be distributed with the program files in a directory specified in the FGLRESOURCEPATH environment variable.

Setting the correct locale

The locale (LANG/LC_ALL) corresponding to the encoding used in the .42s files must be set before starting the application. If the locale is wrong, the strings will not be loaded properly.

How does the runtime system load the strings?

The .42s compiled string resource files are loaded in the following order of precedence:

  1. The files defined in FGLPROFILE,
  2. A file having the same name as the current program (myprog.42m loads myprog.42s),
  3. A file with the name "default.42s".

Each .42s string resource file is searched in several directories, as described in the FGLRESOURCEPATH reference topic.

String resource file sharing

Like .42m program pcode files, the .42s string resource files are shared by all fglrun processes running on the computer: The string file is loaded into memory with the mmap operating system function.

Defining a list of string files in FGLPROFILE

Specify a list of compiled string files with entries in the FGLPROFILE configuration file with the fglrun.localization entries.

First, define the total number of files with:
fglrun.localization.file.count = integer
For each file, define the filename (with the .42s extension), including an index number (start index must be 1):
fglrun.localization.file.index.name = "filename.42s"

Warning switches can be specified in FGLPROFILE.

If the text of a string is not found at runtime, the runtime system can show a warning, for development purposes.
fglrun.localization.warnKeyNotFound = boolean

By default, this warning switch is disabled.

What happens if a 42s string file is not found?

If the 42s string file was defined with fglrun.localization.* FGLPROFILE entries, it is considered as mandatory, and the runtime system will raise error -8006 if the file is not found. If the progname.42s and default.42s string files are not found, no error is raised, because these are fallback string resource files.

What happens if a string is not defined in a resource file?

If a localized string is not defined in one of the compiled string files, the runtime system uses the string identifier as default text.

What happens if a string is defined more that once?

When a localized string is defined in several compiled string files, the runtime system uses the first string found.

For example, if the string "hello" is defined in program.42s as "hello from program", and in default.42s as "hello from default", the runtime system will use the text "hello from program".

Organizing .42s resource files in distribution directories

A set of .42s files using the same language and codeset is typically copied in a distribution directory with a name identifying the locale.

For example:
/opt/app/resource/strings/en_US.iso8859-15  -- English strings in iso8859-15 code-set
/opt/app/resource/strings/fr_FR.iso8859-15  -- French strings in iso8859-15 code-set
/opt/app/resource/strings/jp_JP.utf8        -- Japanese strings in utf-8 code-set
At runtime, specify the string file search path in the DBPATH/FGLRESOURCEPATH environment variable by adding the name of current locale as sub-directory. For example, to find the correct string files in one of the locale-specific directories shown above, set the FGLRESOURCEPATH variable as follows (UNIX™ shell):
$ echo $LC_ALL
$ FGLRESOURCEPATH="$FGLRESOURCEPATH:/opt/app/resource/strings/$LC_ALL"

Localized string files on mobile devices

On mobile devices, the language is determined by the operating system regional settings.
  • On iOS devices, go to Settings >> General >> Language & Region
  • On Android™ devices, go to Settings >> General Management >> Language and Input
The selected language is identified by a locale code following the ISO 639 standard. Below are some language code examples; see the mobile OS documentation for information about available languages and their corresponding ISO 639-x codes.
  • en - English (for all regions)
  • en_US - English in the United States
  • en_GB - English in the United Kingdom
On startup, the mobile app will search for localized string files (.42s) in the following directories:
  1. appdir/full-locale-code: the sub-directory with language and category/region codes. For example for an English-US locale: appdir/en_US.
  2. appdir/language-code: the sub-directory with language code. For example for an English-US locale: appdir/en.
  3. appdir/defaults: the fallback directory where default string files are located.

In order to localize your application, you simply need to place your .42s localized string files in the appropriate language sub-directory.

If the .42s filenames do not match the main program name, define the list of localized strings files in the app's fglprofile file.

If you want to distinguish language categories (Simplified/Tradition Chinese), or if you want to use different texts for territories that share the same language (English in USA or Great Britain), create language sub-directories with the exact OS locale identifier:

  • For English in the USA, use "en_US"
  • For English in the United Kingdom, use "en_GB"
  • For English in Canada, use "en_CA"
  • etc...

If the language category or region can be ignored, create language sub-directories with names matching the language identifier only:

  • For English, use "en"
  • For French, use "fr"
  • For German, use "de"
  • etc...
A default set of string files can be provided under appdir/defaults, in case the regional settings of the device do not match one of the locale directories you provide, otherwise the application will stop with error -8006:

For more details about the mobile app directory structures (appdir), see Directory structure for GMA apps and Directory structure for GMI apps.

Selecting the application language at runtime

The program can reset the path to find localized strings at runtime with the base.Application.reloadResources(path) method. This can be used to implement a login dialog, where the end user can choose the application language.

However, the base.Application.reloadResources(path) method will only have an impact on subsequent loaded resources: The localized strings of already loaded .42m modules and .42f forms are left unchanged. Subsequent loaded forms and modules will get localized strings from new resource lookup path. Therefore, this method must be called at the beginning of the program, before loading the first application form.

A typical pattern is to do display an initial form that allows the user to select the language, build the path to the localized strings files corresponding to the selected language, call the base.Application.reloadResources(path) method, and reload the initial form:

                user STRING,
                pswd STRING,
                lang CHAR(2)
           END RECORD,
           path STRING

    -- Login dialog with language selection
    LET rec.lang = "en" -- Can be "en", "fr", "ge" ...
    WHILE NOT done
        LET path = os.Path.join(base.Application.getProgramDir(), rec.lang)
        CALL base.Application.reloadResources(path)
        OPEN FORM f FROM "main"
        DISPLAY FORM f
            ON CHANGE lang
               EXIT INPUT -- restarts the input with the new locale settings
            ON ACTION cancel
               EXIT PROGRAM
            AFTER INPUT
               LET done = TRUE
        END INPUT
    -- Here starts the real application code