[% FILTER gettext %] The "World Of Themes" is the ultimate source of templates for the Template Toolkit. [% END %]
``` This shows three different ways of localizing strings. You can use the function `gtx.gettext()`, the filter `gettext` with pipe syntax, or the same filter with block syntax. The result is always the same. The string will be recognized as translatable by `xgettext-tt2` and it will be translated into the selected language, when rendering the template. #### Interpolating Strings Into Translations One important thing to understand is that the argument to the gettext functions or filters is the lookup key into the translation database, when the template gets rendered. That implies that this key has to be invariable and must not use any interpolated variables. ```html [% USE gtx = Gettext('com.mydomain.www', lang) %] [% gtx.gettext("Hello, $firstname $lastname!") %] ``` This template code is syntactically correct and will also render correctly. But `xgettext-tt2` will bail out on it with an error message like templates.html:3: Illegal variable interpolation at "$" The function `gettext()` will receive the interpolated string as its argument, and that is not the same as the string that the extractor program `xgettext-tt2` sees. And that means that the translation cannot be found. The correct way to interpolate strings uses `xgettext()`: ```html [% USE gtx = Gettext('com.mydomain.www', lang) %] [% gtx.xgettext("Hello, {first} {last}!", first => firstname, last => lastname) %] [% "Hello, {first} {last}!" | xgettext(first => firstname, last => lastname) %] [% FILTER xgettext(first => firstname, last => lastname) %] Hello, {first} {last}! [% END %] ``` One additional benefit of this is that the extractor program `xgettext-tt2` will also mark these strings with the flag "perl-brace-format". When the translation from the `.po` file gets compiled into an `.mo` file, the compiler `msgfmt` checks that the translated strings contains exactly the same placeholders as the original. One thing that you should also avoid is to assemble strings in the template source code. Do *not*: ```html [% gtx.gettext("Please contact") %] [% name %] [% gtx.gettext("for help about the") %] [% package %] [% gtx.gettext("software.") %] ``` This will result in three translatable text snippets "Please contact", "for help about the", and "software." that are hard to translate without context. Besides it makes illegal assumptions about the word order in translated sentences. Instead, use `xgettext()` and write in complete sentences with placeholders. By the way, the `x` in the function `xgettext()` stands for *eXpand* while the `x` in the program `xgettext-tt2` or GNU Gettext's `xgettext` program stands for *eXtract*. #### Plural Forms Do *not* write this: ```html [% IF num != 1 %] [% gtx.xgettext("{number} documents deleted!", number => num) %] [% ELSE %] [% gtx.gettext("One document deleted!") %] [% END %] ``` This assumes that every language has one singular and one plural (and no other forms) and that the condition that selects the correct form is always `COUNT != 1`. But this is wrong for many languages for example Russian (two plural forms), Chinese (no plural), French (different condition), and many more. Write instead: ```html [% USE gtx = Gettext('com.mydomain.www', lang) %] [% gtx.nxgettext("One document deleted.", "{count} documents deleted." num, count => num) %] ``` The function `nxgettext()` receives the singular and plural form as the first and second argument, followed by the number of items, followed by an arbitrary number of key/value pairs for interpolating variables in the strings. There is also a function `ngettext()` that does not expand its first two arguments. You will find out that you almost never need that function. You can also use `nxgettext()` and `ngettext()` as filters. But the necessary code is awkward, and their use is therefore not recommended. #### Ambiguous Strings (message contexts) Sometimes an English string has different meanings in other languages: ```html [% USE gtx = Gettext('com.mydomain.www', lang) %] [% gtx.gettext("State:") %] [% IF state == '1' %] [% gtx.pgettext("state", "Open") %] [% ELSE %] [% gtx.gettext("Closed") %] [% END %] [% gtx.pgettext("action", "Open") %] ``` The function `pgettext()` works like gettext but has one extra argument preceding the string, the so-called message context. The string extractor `xgettext-tt2` will now create two distinct messages "Open", one with the context "state", the other one with the context "action". The sole purpose of this context is to disambiguate the string "Open" for languages where the verb ("to open") and the adjective ("the door is *open*") has two distinct translations. You will normally use this function, when a translator asks you to do so, but not on your own behalf. There is also a function `pxgettext()` that supports placeholder interpolation, and `npxgettext()` that has the following semantics: ```perl npxgettext(CONTEXT, SINGULAR, PLURAL, COUNT, KEY1 => VALUE1, KEY2 => VALUE2, ...) ``` #### More Esoteric Functions The [API documentation](lib/Template/Plugin/Gettext.pod#user-content-FUNCTIONS) contains some more functions and filters that are available for completeness. You will never need them in normal projects. #### Translator Hints You can add comments to the source code that are copied into the `.po` file as hints for the translators. This will look like this: ```html [% USE gtx = Gettext('com.mydomain.www', lang) %] [% gtx.gettext("Sun") %] ``` In order to make that work, you have to invoke the extractor program `xgettext-tt2` like this: xgettext-tt2 --add-comments=TRANSLATORS: t1.html t2.html ... #### Modifying Flags In rare situations, you may need the following: ```html [% USE gtx = Gettext('com.mydomain.www', lang) %] [% gtx.xgettext("Value: {value}", value => whatever) %] ``` Normally, the argument of `xgettext()` will be flagged in the `.po` file with "perl-brace-format", and a translation will fail to compile if the translation does not contain exactly the same placeholders as the original does. You can override that default behavior for individual messages by placing a comment containing the string "xgettext:" directly in front of the string. ### Translation Workflow The translation workflow is the standard workflow known from GNU Gettext. All files relevant for translations are conventionally kept in a subdirectory `po`. You can save time if you use the seed project [Template-Plugin-Gettext-Seed](https://github.com/gflohr/Template-Plugin-Gettext-Seed) as a base. It contains a directory `po` ready for use, with --- at your choice --- a Makefile or a script `po-make.pl` that automates the entire translation workflow. It is also prepared for extracting strings from other sources than template files. In that example, these are Perl source files, but it will work in a similar fashion for other programming languages. But rolling your own version is also simple. Just read on. #### Extracting Strings With `xgettext-tt2` Extracting translatable strings from templates for the Template Toolkit 2 is as easy as: ```shell $ xgettext-tt2 TEMPLATE.... ``` This will scan all files given as arguments for translatable strings and create a file `messages.po` with the strings found. The normal invocation of `xgettext-tt2` is normally a little bit more sophisticated: ```shell $ xgettext-tt2 --files-from=POTFILES \ --output=com.mydomain.www.pot \ --add-comments=TRANSLATORS: --from-code=utf-8 \ --force-po ``` You can, of course, write everyting in one line and omit the backslashes. Specifying all input files as arguments on the command-line can quickly become unwieldy. It is more common to put the list of input files into a text file, each input file on one line, and instruct `xgettext-tt2` to read it with the option `--files-from`. The name of the file is by convention `POTFILES`. The output file is normally a file `TEXTDOMAIN.pot`, where `TEXTDOMAION` is the identifier selected in the templates. The reverse hostname of the server serving the rendered templates is a good choice. If you want to be able to give hints to translators in the source files, you have to specify the trigger string --- normally "TRANSLATORS:" --- with the option `--add-comments`. Specifying an empty string (`--add-comments=''`) instructs `xgettext-tt2` to copy all comments into the `.pot` file. If your templates contain characters outside of US-ASCII, you should specify the character set of the template files with the option `--from-code=CODESET`. The option `--force-po` instructs `xgettext-tt2` to write an output file even if no translatable strings had been found. But this is a matter of taste. Omit the option, if you prefer it. `xgettext-tt2` has a lot more options. They are mostly compatible with the ones of `xgettext` from GNU gettext for C, Perl, and a lot more languages. See the [documentation for GNU Gettext's xgettext](https://www.gnu.org/software/gettext/manual/html_node/xgettext-Invocation.html) and the documentation for [Locale::XGettext](https://github.com/gflohr/Locale-XGettext/blob/master/lib/Locale/XGettext.pod) for more information. By the way, why is the ouput file a `.pot` file and not a `.po` file? It is the *template* for the `.po` files for the individual languages. You never edit that file, but re-generate it, whenever the source files have changed. Hence, it only contains strings in the original, in the base language. #### Creating Translation Files For each supported language (except for the base language) you should create a file `LL.po`, where `LL` is the two-letter language code for that language, for example `fr.po`, `de.po`, or `it.po`. You can also specify the combination of language and country like in `de_DE.po` or `pt_BR.po`. One option for that is to simply copy the `.pot` file and edit the header accordingly. It is normally easier to do that with the program `msginit`: ``` $ msginit --input=com.mydomain.www.pot --locale=fr ``` Replace `TEXTDOMAIN.pot` with the name of the `.pot` file, and `fr` with the language in question. This will prefill a lot of fields in the `.po` file. #### Compiling Translation Files The translated `.po` files are compiled with the program `msgfmt`: ```shell $ msgfmt --check --statistics --verbose -o fr.mo fr.po fr.po: 212 translated messages, 1 fuzzy translation, 3 untranslated messages. ``` This will compile the translation file `fr.po` into a binary file `fr.mo`. It also checks the translations for formal errors and print statistics about the number of translated and untranslated strings. #### Installing Translation Files The plugin does not use `.po` files for looking up translations but the binary `.mo` files. But it has to find them. You have to decide for one of the directories that `Template::Plugin::Gettext` searches for translations. The default order is: * `@INC/LocaleData` * `/usr/share/locale` * `/usr/local/share/locale` The first line means that every directory `LocaleDir` inside Perl's include directories is searched for translation files. Keep in mind, that for security reasons the current directory (`.`) is nowadays often *not* in Perl's `@INC`. Let's assume that `/var/www/lib` is in Perl's @INC. You would then install the French translation file `fr.mo` as `/var/www/lib/LocaleData/fr/LC_MESSAGES/com.mydomain.www.mo`. `TEXTDOMAIN` is a placeholder for the textdomain you have selected (and `LC_MESSAGES` is *not* a placeholder but a real directory name). That is good except for the fact that `/var/www/lib` is usually not in Perl's `@INC`. But you can change that where you invoke the template processor: ```perl BEGIN { unshift @INC, '/var/www/lib'; } use Template; Template->new->process('template.html', $data); ``` You can completely override the default search order in the templates: ```html [% USE gtx = Gettext('com.mydomain.www', lang, 'utf-8', '/var/www/locale', '/srv/www/locale')] ``` Now, the French translation would be searched in `/var/www/locale/fr/LC_MESSAGES/com.mydomain.www.mo` and `/var/www/locale/fr/LC_MESSAGES/com.mydomain.www.mo`. #### Updating Translation Files Translations may become obsolete, when the source templates change. In this case, you have to merge the new set of translatable strings into the existing translation files. Fortunately, GNU Gettext makes this easy: ```shell $ xgettext-tt2 --files-from=POTFILES \ --output=com.mydomain.www.pot \ --add-comments=TRANSLATORS: --from-code=utf-8 \ --force-po $ cp fr.po fr.old.po $ msgmerge fr.old.po com.mydomain.www.pot -o fr.po ....... done ``` You first update the `.pot` file with `xgettext-tt2` so that it contains the current set of translatable strings. You then make a backup of each `.po` file and then invoke the program `msgmerge` for merging the current translations from `fr.old.po` with the new set of strings from `com.mydomain.www.pot` into the updated translation file `fr.po`. The file `fr.po` will now contain the new strings as untranslated entries. Strings that have only slightly change will retain their translations but they will be marked as "fuzzy", so that they can be reviewed by a translator. Entries for strings that are no longer present in the sources are obsoleted. #### Integrating With Other Programming Languages The GNU Gettext framework is available for a lot of programming languages and it is not uncommon that two or more of these languages are mixed in a project. It is beneficial in these cases to use a common translation base for all used technologies. `xgettext-tt2` is based on [`Locale-XGettext`](https://github.com/gflohr/Locale-XGettext) and therefore not only understands Template Toolkit templates but also `.po` and `.pot` files as input. GNU Gettext's xgettext has the same feature. Accumulating all translatable strings from the different technologies is therefore very easy. If you have a project that uses Template Toolkit for rendering web pages and Perl for the business logic you first extract strings from your Perl files --- as usual --- with `xgettext` from GNU gettext into a temporary file, for example `plfiles.pot`. Then you extract the strings from the templates with `xgettext-tt2` from this library, but you specify `plfiles.pot` as an additional input file. And now the output file of `xgettext-tt2` contains all the strings from the template files *plus* those from the Perl files in `plfiles.pot`. Of course, you can also do it the other way round, extract with `xgettext-tt2` into `ttfiles.pot`, and then feed that as an additional input file to GNU Gettext's `xgettext`. You can use the seed project [Template-Plugin-Gettext-Seed](https://github.com/gflohr/Template-Plugin-Gettext-Seed) as a fully functional starting point for such setups. ## Bugs Please report bugs at [https://github.com/gflohr/Template-Plugin-Gettext/issues](https://github.com/gflohr/Template-Plugin-Gettext/issues) ## Author Template-Plugin-Gettext was written by [Guido Flohr](http://www.guido-flohr.net/).