Difference between revisions of "GettextForWesnothDevelopers"

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This page is used to help Wesnoth developers to work with the internationalization (i18n) system, based on GNU gettext.
+
This page is used to help Wesnoth developers and UMC authors to work with the internationalization (i18n) system, based on GNU gettext.
  
Warning: this page is outdated.
+
==  General design of gettext use  ==
 +
 
 +
Gettextized programs usually contain the English strings within the source code, with calls like ''puts (_("Hello world."));'', so that the binary can work (in English) when the system does not support i18n.
 +
 
 +
=== Textdomains ===
 +
 
 +
Gettext splits translations into domains. For Wesnoth, the general idea is to use distinct textdomains for each campaign or add-on, so that UMC authors can easily ship translations together with their campaigns. These domains are covered in more depth in [[GettextForTranslators]].
 +
 
 +
The convention is to name each domain using the name of the add-on, or just its initials. For example, ''wesnoth-utbs'' or ''wesnoth-Son_of_Haldric''. For UMC, it probably makes sense to use the full name to ensure that it doesn't clash with another add-on.
 +
 
 +
=== Caret hints ===
 +
 
 +
Some strings look the same in English but should not necessarily look identical in translations. To handle this, those strings can be prefixed with any descriptive string and a '''^''' character. For users viewing in '''en_US''', these hints will be automatically removed from the string before showing it to the user.
 +
 
 +
{{DevFeature1.15|2}} if the string contains more than one '''^''', the descriptive string ends at the first '''^''', everything following the first '''^''' will be shown to the user.
 +
 
 +
{{DevFeature1.15|18}} When using gettext's Plural Forms, these prefixes can and should be used in both the singular and the plural.
 +
 
 +
=== UTF-8 ===
 +
 
 +
For translation, all C++, WML and Lua files should be in UTF-8. As noted in the [[Typography_Style_Guide]], some punctuation should be used that's outside of the ASCII subset.
 +
 
 +
==  Marking up strings in C++  ==
 +
 
 +
In C++, you can mark up strings for translations using the <syntaxhighlight lang=c++ inline>_("A translation")</syntaxhighlight> and <syntaxhighlight lang=c++ inline>_n("Translation", "Translations", int)</syntaxhighlight> macros. The <code>_n</code> macro is to be used if the string has a singular and plural form.
 +
 
 +
If the string contains any placeholders, do '''not''' use <code>snprintf</code>. Use <code>vgettext</code> instead, or <code>vngettext</code> for any int placeholders.
 +
 
 +
You can also add comments for translators directly above the string - use the keyword <code>TRANSLATORS:</code> for that. The comment must be placed in the line ''immediately'' above the translateable string, like this:
 +
 
 +
<syntaxhighlight lang=c++>
 +
int handfuls = 2;
 +
const std::string translated_text = vngettext(
 +
    // TRANSLATORS: Yum!
 +
    "$handfuls handful of $taste potatoes",
 +
    "$handfuls handfuls of $taste potatoes",
 +
    handfuls,
 +
    utils::string_map({ {"handfuls", handfuls}, {"taste", "yummy"} }));
 +
</syntaxhighlight>
 +
 
 +
The following code will ''not'' work for including the comment:
 +
 
 +
<syntaxhighlight lang=c++>
 +
int handfuls = 2;
 +
// TRANSLATORS: Yuck!
 +
const std::string translated_text = vngettext(
 +
    "$handfuls handful of $taste potatoes",
 +
    "$handfuls handfuls of $taste potatoes",
 +
    handfuls,
 +
    utils::string_map({ {"handfuls", handfuls}, {"taste", "yucky"} }));
 +
</syntaxhighlight>
 +
 
 +
You can also use multiline comments:
 +
 
 +
<syntaxhighlight lang=c++>
 +
int handfuls = 2;
 +
const std::string translated_text = vngettext(
 +
    /* TRANSLATORS: Yum!
 +
      Best potatoes ever! */
 +
    "$handfuls handful of $taste potatoes",
 +
    "$handfuls handfuls of $taste potatoes",
 +
    handfuls,
 +
    utils::string_map({ {"handfuls", handfuls}, {"taste", "yummy"} }));
 +
</syntaxhighlight>
 +
 
 +
By default, all strings in C++ belong to the "wesnoth" textdomain. If a different textdomain is required, you can add a textdomain binding at the top of the source file, before any include statements. A textdomain binding looks like this: <syntaxhighlight lang=c++>#define GETTEXT_DOMAIN "wesnoth-lib"</syntaxhighlight>
 +
 
 +
You should avoid placing translatable strings in C++ headers if at all possible. Though there are a few places where it may be unavoidable, such as if templates are in use, it creates the risk of the strings sometimes being looked up in the wrong textdomain if the header is included in multiple files with different textdomains. If possible, always factor the translatable strings out into a source file.
 +
 
 +
== Marking up strings in WML ==
 +
 
 +
=== The textdomain bindings ===
 +
 
 +
All files with translatable strings must declare which textdomain they use, which is normally done by putting ''#textdomain'' on the first line of each .wml file. See the example below:
 +
 
 +
<syntaxhighlight lang=wml>
 +
#textdomain wesnoth-Son_of_Haldric
 +
 
 +
[unit_type]
 +
    id=Mu
 +
    name= _ "Mu"
 +
    # ...
 +
[/unit_type]
 +
</syntaxhighlight>
 +
 
 +
Note that it is highly recommended that the first textdomain binding be on the first line of the file. Otherwise, odd stuff may happen.
  
== How to move strings from one textdomain to another  ==
+
=== The translatable strings ===
  
* run ''make -C po update-po'' and commit, to be sure to only commit your own changes
+
To mark a string as translatable, just put an underscore ( _ ) in front of the string you wish to be marked as translatable, like the example below:
* move the file into the corect po/*/POTFILES.in
 
* add or change ''#define GETTEXT_DOMAIN "wesnoth-lib"'' at top of the file, before the includes
 
* update the target POT file to include the new strings in its template (eg. ''make -C po/wesnoth-editor
 
wesnoth-editor.pot-update'')
 
* copy the translations using utils/po2po (eg. ''./utils/po2po wesnoth wesnoth-editor'')
 
* update the source POT file to get rid of the old strings (eg. ''make -C po/wesnoth update-po''), then preferably
 
remove the translation from obsolete strings in all languages, to make sure, in case the strings have to move back,
 
that
 
any translation update gets used instead of the current one)
 
* check ''cvs diff'' and commit
 
  
== General design of gettext use ==
+
<syntaxhighlight lang=wml>
 +
name= _ "Mu"
 +
</syntaxhighlight>
 +
 
 +
==== Notes to the translators ====
 +
 
 +
If you think a translatable string needs additional guidance to be translated properly, you can provide a special comment that will be seen by the translators. Some hints are generated automatically, but in general if you have to wonder whether a hint is needed then it probably is. The context of the scenario isn't obvious in the translation tools, and you can't assume that the strings are shown to the translator in the same order that they appear in the WML file.
 +
 
 +
Just begin the comment with '#po:' or '# po:' above the string in question. This must be on the line (or lines) immediately before the string that the hint applies to:
 +
 
 +
<syntaxhighlight lang=wml>
 +
#po: "northern marches" is *not* a typo for "northern marshes" here.
 +
#po: In archaic English, "march" means "border country".
 +
story=_ "The orcs were first sighted from the north marches of the great forest of Wesmere."
 +
</syntaxhighlight>
 +
 
 +
The wmlxgettext tool will automatically generate hints for some tags, in addition to hints from '# po:' comments:
 +
 
 +
* For ''[message]'': the ''id'', ''speaker'', ''role'' or ''type'' used to choose the speaker
 +
* For ''[object]'': the ''id''
 +
* For ''[unit]'': the ''id'' and ''unit_type''
 +
* For ''[unit_type]'': the ''id'' and ''race''
 +
* For ''[objective]'': whether it's ''condition=win'' or ''condition=lose''
 +
 
 +
==== Things to avoid ====
 +
 
 +
Note that there are certain things you should never do. For example, '''never''' mark an empty string as translatable, for wmlxgettext (the tool that extracts strings from WML) will abort upon detecting one. Therefore, what is seen below should never be done:
 +
 
 +
<syntaxhighlight lang=wml>
 +
name= _ ""
 +
</syntaxhighlight>
 +
 
 +
Also, never put macro arguments in a translatable string, for it will not work. The reason for this is that the preprocessor does its job before gettext, thus gettext will try to replace a string that does not exist. Therefore, what is shown below should not be done:
 +
 
 +
<syntaxhighlight lang=wml>
 +
name= _ "{TYPE} Mu"
 +
</syntaxhighlight>
 +
 
 +
To show why it will not work:
 +
 
 +
<syntaxhighlight lang=wml>
 +
#define UNIT_NAME TYPE
 +
    name= _ "{TYPE} Mu"
 +
#enddef
 +
 
 +
{UNIT_NAME ( _ "Sword")}
 +
{UNIT_NAME ( _ "Bow")}
 +
</syntaxhighlight>
 +
 
 +
Translation catalogues would have this: "{TYPE} Mu", therefore gettext will look for it even though it will not exist because we, in fact, have these after the preprocessor is done:
 +
 
 +
<syntaxhighlight lang=wml>
 +
name= _ "Sword Mu"
 +
name= _ "Bow Mu"
 +
</syntaxhighlight>
 +
 
 +
Since those are not in the catalogues, they will not get translated.
 +
 
 +
=== Gender-specific strings ===
 +
 
 +
Several tags, including ''[message]'', ''[abilities]'' and ''[trait]'', can choose different strings based on the gender of the unit. In English the two versions are likely to be the same, but other languages may have gender-specific words for 'I' or 'me'.
 +
 
 +
<syntaxhighlight lang=wml>
 +
[message]
 +
    speaker=student
 +
    message= _ "Have you found an orc for me to fight, huh? A troll?"
 +
    female_message= _ "female^Have you found an orc for me to fight, huh? A troll?"
 +
[/message]
 +
</syntaxhighlight>
 +
 
 +
The convention in WML is, as above, to use ''message='' and ''female_message='', with the latter string including the prefix ''female^''. The mechanism also supports ''male_message='', but all units will fall back to using the plain ''message='' value if there isn't gender-specific version that matches their gender.
 +
 
 +
The message is chosen based on the gender of the speaking unit. To change the message based on the gender of another unit requires separate ''[message]'' tags:
 +
 
 +
<syntaxhighlight lang=wml>
 +
[if]
 +
    [have_unit]
 +
        id=student
 +
        gender=male
 +
    [/have_unit]
 +
    [then]
 +
        [message]
 +
            speaker=Delfador
 +
            message= _ "Young man, you have $student_hp hitpoints and a sword. I’m fairly sure you’ll win."
 +
        [/message]
 +
    [/then]
 +
    [else]
 +
        [message]
 +
            speaker=Delfador
 +
            message= _ "female^Young lady, you have $student_hp hitpoints and a sword. I’m fairly sure you’ll win."
 +
        [/message]
 +
    [/else]
 +
[/if]
 +
</syntaxhighlight>
 +
 
 +
Using a macro to encapsulate most of that can be useful. The example above is from the tutorial, after expanding the ''GENDER'' macro which is defined in data/campaigns/tutorial/utils/utils.cfg.
 +
 
 +
=== Reusing mainline translations ===
 +
 
 +
You can reuse translations for strings in mainline domains by using multiple textdomain bindings:
 +
 
 +
<syntaxhighlight lang=wml>
 +
# textdomain wesnoth-Son_of_Haldric
 +
 
 +
[unit_type]
 +
    id=Mu
 +
    name= _ "Mu"
 +
    # ...
 +
 
 +
    [attack]
 +
        id=sword
 +
        #textdomain wesnoth-units
 +
        description= _ "sword"
 +
        # ...
 +
    [/attack]
 +
 
 +
    #textdomain wesnoth-Son_of_Haldric
 +
    # ...
 +
[/unit_type]
 +
</syntaxhighlight>
 +
 
 +
Of course, if you use bindings for multiple textdomains, make sure the right parts of the file are bound to the right domains. Also, never try to use the mainline campaigns’ domains, for there is no guarantee that the mainline campaigns will be available on all setups. So, only use the core domains: wesnoth, wesnoth-editor, wesnoth-lib, wesnoth-help, and wesnoth-units.
 +
 
 +
==== The gettext helper file ====
 +
 
 +
A gettext helper file is a lovely file that makes reusing mainline translations nice and easy, by having all strings that should use a specific textdomain in a single file. It is also more wmllint-friendly.
 +
 
 +
Here is an example of a gettext helper file. The macro names start with 'SOH_' to ensure that they don't clash with another add-on's macros (assuming that this add-on is Son_of_Haldric).
 +
 
 +
<syntaxhighlight lang=wml>
 +
#textdomain wesnoth-lib
 +
 
 +
#define SOH_STR_ICE
 +
_"Ice" #enddef
 +
 
 +
#textdomain wesnoth-units
 +
 
 +
#define SOH_STR_SWORD
 +
_"sword" #enddef
 +
</syntaxhighlight>
 +
 
 +
A typical name for gettext helper files is ''mainline-strings.cfg''.
 +
 
 +
To use it, just wire it into your add-on and use the macros:
 +
 
 +
<syntaxhighlight lang=wml>
 +
[attack]
 +
    id=sword
 +
    name={SOH_STR_SWORD}
 +
    # ...
 +
[/attack]
 +
 
 +
[terrain_type]
 +
    id=ice2
 +
    name={SOH_STR_ICE}
 +
    # ...
 +
[/terrain_type]
 +
</syntaxhighlight>
 +
 
 +
=== Unbalanced WML macros ===
 +
 
 +
WML macros can be ''unbalanced'', meaning that they either include a [tag] without the corresponding [/tag] or a [/tag] before the corresponding [+tag]. These macros are expected to be used in a place where the [tag] is already open. Writing new macros using this isn't recommended; instead please ask in the WML Workshop forum about better ways to do it.
 +
 
 +
When generating the .pot files for translation, wmlxgettext may stop with one of the errors
 +
* error: Son_Of_Haldric/utils/abilities.cfg:29: unexpected closing tag '[/abilities]' outside any scope.
 +
* error: Son_Of_Haldric/utils/abilities.cfg:300: End of WML file reached, but some tags were not properly closed. (nearest unclosed tag is: [abilities])
 +
 
 +
Suppose abilities.cfg line 29 is in the definition of SOH_ABILITY_BLITZ. To get the .pot file generated, the simplest change is to use ''# wmlxgettext'' comments to add the missing opening or closing tags:
 +
 
 +
<syntaxhighlight lang=wml>
 +
# wmllint: unbalanced-on
 +
# wmlxgettext: [abilities]
 +
#define SOH_ABILITY_BLITZ
 +
    [dummy]
 +
        id=soh_blitz
 +
</syntaxhighlight>
 +
... several lines of code, none of which are an ''#enddef'' ...
 +
<syntaxhighlight lang=wml>
 +
[+abilities]
 +
#enddef
 +
# wmlxgettext: [/abilities]
 +
# wmllint: unbalanced-off
 +
</syntaxhighlight>
 +
 
 +
== Marking up strings in Lua ==
 +
 
 +
In Lua code, textdomains are a callable object that looks up a string. This has support for both singular and plural strings. By convention, the name <code>_</code> is usually used for the textdomain object.
 +
 
 +
The following sample code demonstrates how to fetch translatable strings in Lua:
 +
 
 +
<syntaxhighlight lang=lua>
 +
local _ = wesnoth.textdomain "wesnoth"
 +
 
 +
-- Look up a normal string:
 +
local win_condition = _ "Defeat enemy leader(s)"
 +
 
 +
-- Hints for the translators start with "po:", as in WML:
 +
-- po: Floating text shown when a unit with the "feeding" ability gets a kill
 +
local text = stringx.vformat(_"+$value max HP", { value = feeding.value})
 +
</syntaxhighlight>
 +
 
 +
Plural strings are supported since Wesnoth 1.14:
 +
<syntaxhighlight lang=lua>
 +
local turn_count = 5
 +
turn_counter = _("this turn left", "%d turns left", turn_count)
 +
turn_counter = tostring(turn_counter):format(turn_count)
 +
 
 +
-- For readability, the example's strings are slightly different to the real code.
 +
-- The real strings have brackets in the text shown to the player.
 +
</syntaxhighlight>
 +
 
 +
In Wesnoth 1.15, variables can be interpolated using names:
 +
<syntaxhighlight lang=lua>
 +
-- Look up a plural string, using the preferred style (as of Wesnoth 1.15.3):
 +
local turn_count = 5
 +
turn_counter = _("this turn left", "$remaining_turns turns left", turn_count)
 +
turn_counter = turn_counter:vformat{remaining_turns = turn_count}
 +
</syntaxhighlight>
 +
 
 +
== The textdomain tag ==
 +
 
 +
To tell the engine where to search for the .po and .mo files, each textdomain needs a ''[textdomain]'' tag. For add-ons and mainline campaigns, the tag is usually placed inside of the _main.cfg. This is a top-level tag, so should be outside the ''[campaign]'' or ''[modification]'' tag.
 +
 
 +
Translatable strings from C++ and Lua use the same textdomains as WML; this WML tag tells the engine where to search for these strings irrespective of which programming language the string appeared in.
 +
 
 +
<syntaxhighlight lang=wml>
 +
[textdomain]
 +
    name="wesnoth-Son_of_Haldric"
 +
    path="data/add-ons/Son_of_Haldric/translations"
 +
[/textdomain]
 +
</syntaxhighlight>
 +
 
 +
The .po (or .mo) files will be loaded from a subdirectory of the ''translations'' directory.
 +
 
 +
== Generating the .pot and .po files for UMC ==
 +
 
 +
For each language, Wesnoth will search for a .po file containing the translations. How to create that file will be explained below, but first the overview of where it should go.
 +
 
 +
Continuing with the Son of Haldric example, the Swedish translation would be in the file ''data/add-ons/Son_of_Haldric/translations/wesnoth-Son_of_Haldric/sv.po''.
 +
 
 +
* ''data/add-ons/Son_of_Haldric/translations'' comes from the ''[textdomain]'' tag's ''path''
 +
* ''wesnoth-Son_of_Haldric'' is the textdomain's name
 +
* ''sv'' is the language code for Swedish. The codes for each language are given in the big table on [https://www.wesnoth.org/gettext/ https://www.wesnoth.org/gettext/] .
 +
 
 +
Wesnoth 1.14 (but not 1.12) supports reading .po files directly, so when you add the .po file and the new translation should appear as soon as you refresh the cache.
 +
 
 +
=== Generating the .pot file ===
 +
 
 +
The template (.pot) file contains all of the strings that need to be translated in the .po files, but without the translations.
 +
 
 +
The .pot is generated from WML and Lua files using a tool called wmlxgettext. With Wesnoth 1.14.5 and later, this is shipped with Wesnoth itself as part of the [[Maintenance_tools]] and can be used from the Maintenance Tools' GUI. At the moment it's not documented on that page, but if you follow the instructions to get GUI.pyw running then you'll see there's a wmlxgettext tab.
 +
 
 +
Pre-1.13 instructions on how to get and use it are in Nobun's [https://r.wesnoth.org/p617733 forum posting].
 +
 
 +
==== Error messages from wmlxgettext ====
 +
 
 +
If you get the error from ''wmlxgettext'' of "UTF-8 Format error. Can't decode byte 0x91 (invalid start byte).", and the line in question has a curly quotation mark, that likely means that your text editor is using the Windows-1252 character set, and you need to replace the Windows quotes with their Unicode equivalents, see [[Typography_Style_Guide]] and your editor's documentation for more info. The same applies if the error message says 0x92, 0x93 or 0x94.
 +
 
 +
If you get either "unexpected closing tag '[/''something'']' outside any scope" or "End of WML file reached, but some tags were not properly closed. (nearest unclosed tag is: [''something''])" then see [[#Unbalanced_WML_macros]] above.
 +
 
 +
=== Generating the .po files for each language ===
  
Gettextized programs usually contain the English strings within the source code, with calls like ''printf (_("Hello world."));'', so that the binary can work (in English) when the system does not support i18n. However, in Wesnoth, all strings were moved into ''translations/english.cfg'', and fetched using a label, like in ''translate_string("hello_world");''.
+
Each .po file can start as a simple copy of the .pot file. Either the author or the translator copies the template to the language-specific filename, and then the work of [[GettextForTranslators]] happens on those copies.
  
So we will need to put such strings (mostly GUI material) back into the C++ files. That part will be quite easy, except we'll have to deal with importing existing translations. We will use the ''wesnoth'' text domain for this (that is, a single wesnoth.po file for each language).
+
Some .po editors, for example poedit, will recognise that the .pot is a template, and automatically suggest saving to a different filename. The poedit editor can also update a .po file based on changes to the .pot file.
  
The general idea for strings in WML files is to use distinct text domains for each campaign, so that campaign writers can easily ship translations together with their campaigns. It will require WML files to declare which text domain they belong to.
+
=== Generating the .mo files for UMC ===
  
If some strings look the same in English but should not necessarily look identical in translations (eg. all those prefix/suffix strings, many of which are empty in English). To hande this, those strings can be prefixed with any descriptive string and a ''^'' character, thanks to the ''sgettext'' implementation partly stolen from the gettext manual (eg. ''foo_prefix = _ "foo prefix^"'')
+
For Wesnoth 1.14, it's generally not necessary to compile the .po files to .mo files. The mainline translations still use .mo files for better performance, but UMC authors can skip the .mo compilation stage.
  
 
== See Also ==
 
== See Also ==
Line 31: Line 366:
 
* [[WesnothTranslations]]
 
* [[WesnothTranslations]]
 
* http://www.gnu.org/software/gettext/
 
* http://www.gnu.org/software/gettext/
 +
* [https://www.gnu.org/software/gettext/manual/html_node/Preparing-Strings.html#Preparing-Strings GNU gettext manual on preparing translatable strings]
 
* [[GetText]]
 
* [[GetText]]
  
 
[[Category:Development]]
 
[[Category:Development]]

Revision as of 13:22, 25 October 2021

This page is used to help Wesnoth developers and UMC authors to work with the internationalization (i18n) system, based on GNU gettext.

General design of gettext use

Gettextized programs usually contain the English strings within the source code, with calls like puts (_("Hello world."));, so that the binary can work (in English) when the system does not support i18n.

Textdomains

Gettext splits translations into domains. For Wesnoth, the general idea is to use distinct textdomains for each campaign or add-on, so that UMC authors can easily ship translations together with their campaigns. These domains are covered in more depth in GettextForTranslators.

The convention is to name each domain using the name of the add-on, or just its initials. For example, wesnoth-utbs or wesnoth-Son_of_Haldric. For UMC, it probably makes sense to use the full name to ensure that it doesn't clash with another add-on.

Caret hints

Some strings look the same in English but should not necessarily look identical in translations. To handle this, those strings can be prefixed with any descriptive string and a ^ character. For users viewing in en_US, these hints will be automatically removed from the string before showing it to the user.

(Version 1.15.2 and later only) if the string contains more than one ^, the descriptive string ends at the first ^, everything following the first ^ will be shown to the user.

(Version 1.15.18 and later only) When using gettext's Plural Forms, these prefixes can and should be used in both the singular and the plural.

UTF-8

For translation, all C++, WML and Lua files should be in UTF-8. As noted in the Typography_Style_Guide, some punctuation should be used that's outside of the ASCII subset.

Marking up strings in C++

In C++, you can mark up strings for translations using the _("A translation") and _n("Translation", "Translations", int) macros. The _n macro is to be used if the string has a singular and plural form.

If the string contains any placeholders, do not use snprintf. Use vgettext instead, or vngettext for any int placeholders.

You can also add comments for translators directly above the string - use the keyword TRANSLATORS: for that. The comment must be placed in the line immediately above the translateable string, like this:

int handfuls = 2;
const std::string translated_text = vngettext(
    // TRANSLATORS: Yum!
    "$handfuls handful of $taste potatoes",
    "$handfuls handfuls of $taste potatoes",
    handfuls,
    utils::string_map({ {"handfuls", handfuls}, {"taste", "yummy"} }));

The following code will not work for including the comment:

int handfuls = 2;
// TRANSLATORS: Yuck!
const std::string translated_text = vngettext(
    "$handfuls handful of $taste potatoes",
    "$handfuls handfuls of $taste potatoes",
    handfuls,
    utils::string_map({ {"handfuls", handfuls}, {"taste", "yucky"} }));

You can also use multiline comments:

int handfuls = 2;
const std::string translated_text = vngettext(
    /* TRANSLATORS: Yum!
       Best potatoes ever! */
    "$handfuls handful of $taste potatoes",
    "$handfuls handfuls of $taste potatoes",
    handfuls,
    utils::string_map({ {"handfuls", handfuls}, {"taste", "yummy"} }));

By default, all strings in C++ belong to the "wesnoth" textdomain. If a different textdomain is required, you can add a textdomain binding at the top of the source file, before any include statements. A textdomain binding looks like this:

#define GETTEXT_DOMAIN "wesnoth-lib"

You should avoid placing translatable strings in C++ headers if at all possible. Though there are a few places where it may be unavoidable, such as if templates are in use, it creates the risk of the strings sometimes being looked up in the wrong textdomain if the header is included in multiple files with different textdomains. If possible, always factor the translatable strings out into a source file.

Marking up strings in WML

The textdomain bindings

All files with translatable strings must declare which textdomain they use, which is normally done by putting #textdomain on the first line of each .wml file. See the example below:

#textdomain wesnoth-Son_of_Haldric

[unit_type]
    id=Mu
    name= _ "Mu"
    # ...
[/unit_type]

Note that it is highly recommended that the first textdomain binding be on the first line of the file. Otherwise, odd stuff may happen.

The translatable strings

To mark a string as translatable, just put an underscore ( _ ) in front of the string you wish to be marked as translatable, like the example below:

name= _ "Mu"

Notes to the translators

If you think a translatable string needs additional guidance to be translated properly, you can provide a special comment that will be seen by the translators. Some hints are generated automatically, but in general if you have to wonder whether a hint is needed then it probably is. The context of the scenario isn't obvious in the translation tools, and you can't assume that the strings are shown to the translator in the same order that they appear in the WML file.

Just begin the comment with '#po:' or '# po:' above the string in question. This must be on the line (or lines) immediately before the string that the hint applies to:

#po: "northern marches" is *not* a typo for "northern marshes" here.
#po: In archaic English, "march" means "border country".
story=_ "The orcs were first sighted from the north marches of the great forest of Wesmere."

The wmlxgettext tool will automatically generate hints for some tags, in addition to hints from '# po:' comments:

  • For [message]: the id, speaker, role or type used to choose the speaker
  • For [object]: the id
  • For [unit]: the id and unit_type
  • For [unit_type]: the id and race
  • For [objective]: whether it's condition=win or condition=lose

Things to avoid

Note that there are certain things you should never do. For example, never mark an empty string as translatable, for wmlxgettext (the tool that extracts strings from WML) will abort upon detecting one. Therefore, what is seen below should never be done:

name= _ ""

Also, never put macro arguments in a translatable string, for it will not work. The reason for this is that the preprocessor does its job before gettext, thus gettext will try to replace a string that does not exist. Therefore, what is shown below should not be done:

name= _ "{TYPE} Mu"

To show why it will not work:

#define UNIT_NAME TYPE
    name= _ "{TYPE} Mu"
#enddef

{UNIT_NAME ( _ "Sword")}
{UNIT_NAME ( _ "Bow")}

Translation catalogues would have this: "{TYPE} Mu", therefore gettext will look for it even though it will not exist because we, in fact, have these after the preprocessor is done:

name= _ "Sword Mu"
name= _ "Bow Mu"

Since those are not in the catalogues, they will not get translated.

Gender-specific strings

Several tags, including [message], [abilities] and [trait], can choose different strings based on the gender of the unit. In English the two versions are likely to be the same, but other languages may have gender-specific words for 'I' or 'me'.

[message]
    speaker=student
    message= _ "Have you found an orc for me to fight, huh? A troll?"
    female_message= _ "female^Have you found an orc for me to fight, huh? A troll?"
[/message]

The convention in WML is, as above, to use message= and female_message=, with the latter string including the prefix female^. The mechanism also supports male_message=, but all units will fall back to using the plain message= value if there isn't gender-specific version that matches their gender.

The message is chosen based on the gender of the speaking unit. To change the message based on the gender of another unit requires separate [message] tags:

[if]
    [have_unit]
        id=student
        gender=male
    [/have_unit]
    [then]
        [message]
            speaker=Delfador
            message= _ "Young man, you have $student_hp hitpoints and a sword. I’m fairly sure you’ll win."
        [/message]
    [/then]
    [else]
        [message]
            speaker=Delfador
            message= _ "female^Young lady, you have $student_hp hitpoints and a sword. I’m fairly sure you’ll win."
        [/message]
    [/else]
[/if]

Using a macro to encapsulate most of that can be useful. The example above is from the tutorial, after expanding the GENDER macro which is defined in data/campaigns/tutorial/utils/utils.cfg.

Reusing mainline translations

You can reuse translations for strings in mainline domains by using multiple textdomain bindings:

# textdomain wesnoth-Son_of_Haldric

[unit_type]
    id=Mu
    name= _ "Mu"
    # ...

    [attack]
        id=sword
        #textdomain wesnoth-units
        description= _ "sword"
        # ...
    [/attack]
   
    #textdomain wesnoth-Son_of_Haldric
    # ...
[/unit_type]

Of course, if you use bindings for multiple textdomains, make sure the right parts of the file are bound to the right domains. Also, never try to use the mainline campaigns’ domains, for there is no guarantee that the mainline campaigns will be available on all setups. So, only use the core domains: wesnoth, wesnoth-editor, wesnoth-lib, wesnoth-help, and wesnoth-units.

The gettext helper file

A gettext helper file is a lovely file that makes reusing mainline translations nice and easy, by having all strings that should use a specific textdomain in a single file. It is also more wmllint-friendly.

Here is an example of a gettext helper file. The macro names start with 'SOH_' to ensure that they don't clash with another add-on's macros (assuming that this add-on is Son_of_Haldric).

#textdomain wesnoth-lib

#define SOH_STR_ICE
_"Ice" #enddef

#textdomain wesnoth-units

#define SOH_STR_SWORD
_"sword" #enddef

A typical name for gettext helper files is mainline-strings.cfg.

To use it, just wire it into your add-on and use the macros:

[attack]
    id=sword
    name={SOH_STR_SWORD}
    # ...
[/attack]

[terrain_type]
    id=ice2
    name={SOH_STR_ICE}
    # ...
[/terrain_type]

Unbalanced WML macros

WML macros can be unbalanced, meaning that they either include a [tag] without the corresponding [/tag] or a [/tag] before the corresponding [+tag]. These macros are expected to be used in a place where the [tag] is already open. Writing new macros using this isn't recommended; instead please ask in the WML Workshop forum about better ways to do it.

When generating the .pot files for translation, wmlxgettext may stop with one of the errors

  • error: Son_Of_Haldric/utils/abilities.cfg:29: unexpected closing tag '[/abilities]' outside any scope.
  • error: Son_Of_Haldric/utils/abilities.cfg:300: End of WML file reached, but some tags were not properly closed. (nearest unclosed tag is: [abilities])

Suppose abilities.cfg line 29 is in the definition of SOH_ABILITY_BLITZ. To get the .pot file generated, the simplest change is to use # wmlxgettext comments to add the missing opening or closing tags:

# wmllint: unbalanced-on
# wmlxgettext: [abilities]
#define SOH_ABILITY_BLITZ
    [dummy]
        id=soh_blitz

... several lines of code, none of which are an #enddef ...

[+abilities]
#enddef
# wmlxgettext: [/abilities]
# wmllint: unbalanced-off

Marking up strings in Lua

In Lua code, textdomains are a callable object that looks up a string. This has support for both singular and plural strings. By convention, the name _ is usually used for the textdomain object.

The following sample code demonstrates how to fetch translatable strings in Lua:

local _ = wesnoth.textdomain "wesnoth"

-- Look up a normal string:
local win_condition = _ "Defeat enemy leader(s)"

-- Hints for the translators start with "po:", as in WML:
-- po: Floating text shown when a unit with the "feeding" ability gets a kill
local text = stringx.vformat(_"+$value max HP", { value = feeding.value})

Plural strings are supported since Wesnoth 1.14:

local turn_count = 5
turn_counter = _("this turn left", "%d turns left", turn_count)
turn_counter = tostring(turn_counter):format(turn_count)

-- For readability, the example's strings are slightly different to the real code.
-- The real strings have brackets in the text shown to the player.

In Wesnoth 1.15, variables can be interpolated using names:

-- Look up a plural string, using the preferred style (as of Wesnoth 1.15.3):
local turn_count = 5
turn_counter = _("this turn left", "$remaining_turns turns left", turn_count)
turn_counter = turn_counter:vformat{remaining_turns = turn_count}

The textdomain tag

To tell the engine where to search for the .po and .mo files, each textdomain needs a [textdomain] tag. For add-ons and mainline campaigns, the tag is usually placed inside of the _main.cfg. This is a top-level tag, so should be outside the [campaign] or [modification] tag.

Translatable strings from C++ and Lua use the same textdomains as WML; this WML tag tells the engine where to search for these strings irrespective of which programming language the string appeared in.

[textdomain]
    name="wesnoth-Son_of_Haldric"
    path="data/add-ons/Son_of_Haldric/translations"
[/textdomain]

The .po (or .mo) files will be loaded from a subdirectory of the translations directory.

Generating the .pot and .po files for UMC

For each language, Wesnoth will search for a .po file containing the translations. How to create that file will be explained below, but first the overview of where it should go.

Continuing with the Son of Haldric example, the Swedish translation would be in the file data/add-ons/Son_of_Haldric/translations/wesnoth-Son_of_Haldric/sv.po.

  • data/add-ons/Son_of_Haldric/translations comes from the [textdomain] tag's path
  • wesnoth-Son_of_Haldric is the textdomain's name
  • sv is the language code for Swedish. The codes for each language are given in the big table on https://www.wesnoth.org/gettext/ .

Wesnoth 1.14 (but not 1.12) supports reading .po files directly, so when you add the .po file and the new translation should appear as soon as you refresh the cache.

Generating the .pot file

The template (.pot) file contains all of the strings that need to be translated in the .po files, but without the translations.

The .pot is generated from WML and Lua files using a tool called wmlxgettext. With Wesnoth 1.14.5 and later, this is shipped with Wesnoth itself as part of the Maintenance_tools and can be used from the Maintenance Tools' GUI. At the moment it's not documented on that page, but if you follow the instructions to get GUI.pyw running then you'll see there's a wmlxgettext tab.

Pre-1.13 instructions on how to get and use it are in Nobun's forum posting.

Error messages from wmlxgettext

If you get the error from wmlxgettext of "UTF-8 Format error. Can't decode byte 0x91 (invalid start byte).", and the line in question has a curly quotation mark, that likely means that your text editor is using the Windows-1252 character set, and you need to replace the Windows quotes with their Unicode equivalents, see Typography_Style_Guide and your editor's documentation for more info. The same applies if the error message says 0x92, 0x93 or 0x94.

If you get either "unexpected closing tag '[/something]' outside any scope" or "End of WML file reached, but some tags were not properly closed. (nearest unclosed tag is: [something])" then see #Unbalanced_WML_macros above.

Generating the .po files for each language

Each .po file can start as a simple copy of the .pot file. Either the author or the translator copies the template to the language-specific filename, and then the work of GettextForTranslators happens on those copies.

Some .po editors, for example poedit, will recognise that the .pot is a template, and automatically suggest saving to a different filename. The poedit editor can also update a .po file based on changes to the .pot file.

Generating the .mo files for UMC

For Wesnoth 1.14, it's generally not necessary to compile the .po files to .mo files. The mainline translations still use .mo files for better performance, but UMC authors can skip the .mo compilation stage.

See Also