GNU Gettext for Delphi 使用指南

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"GNUgettextforDelphi,C++BuilderandKylix1.2beta使用说明书" GNU gettext 是一个开源工具集，用于软件本地化，使应用程序能够支持多种语言。它最初是为C语言设计的，但随着时间的推移，已经被扩展到支持其他编程环境，包括 Delphi、C++Builder 和 Kylix。这个1.2 beta 版本的说明书由Lars B. Dybdahl, Peter Thornqvist, Jacquez Garcia Vasquez 和 Sandro Wendt 编写，详细介绍了如何在这些环境中利用 GNU gettext 进行本地化工作。 1. **工作原理** GNU gettext 的工作原理主要是通过创建和处理 `.po`（Portable Object）文件。这些文件包含了源代码中的字符串和它们的翻译版本。当程序运行时，gettext 库会根据用户的语言设置加载相应的翻译，从而显示正确的文本。 2. **创建 .po 文件** 为了开始本地化过程，开发者需要从源代码中提取可本地化的字符串，这通常通过 `xgettext` 工具完成。提取出的字符串会被放入 .po 文件，供翻译人员进行翻译。 3. **更多 gettext 函数** 除了基本的 `gettext` 函数外，还有 `ngettext` 用于处理复数形式的字符串，以及 `dcgettext` 和 `dngettext` 用于处理特定上下文的翻译。这些函数使得开发者能更灵活地管理多语言字符串。 4. **资源字符串** 资源字符串是指那些在界面上显示的文本，如按钮标签、菜单项和提示信息。在 Delphi 和 C++Builder 中，这些字符串可能与控件或组件关联，需要特别处理以便于本地化。 5. **表单（Forms）** 本地化表单时，不仅要考虑文本，还要考虑布局，因为不同语言的文本长度可能会有所不同。gettext 提供了处理这些问题的方法，比如动态调整控件大小。 6. **动作（Action）** 在 Delphi 和 C++Builder 中，Action 组件可以包含需要本地化的文本。本地化Action组件涉及到将Action的文字和描述提取出来进行翻译。 7. **解决歧义** 由于同一字符串在不同上下文中有不同含义，可能需要通过`uses`子句或命名空间（domains）来避免翻译冲突。 8. **修改单词** 有时候，为了适应目标语言的语法，可能需要对单词进行变形，例如改变名词的性别或复数形式。 9. **添加空格** 不同语言的标点习惯和空格使用规则不同，可能需要在翻译中添加或删除空格。 10. **域（Domains）** 使用不同的域可以帮助组织和区分不同部分的翻译，例如将用户界面的文本与帮助文档的文本分开。 11. **尾部注释（Trailing comments）** 在 .po 文件中，可以添加尾部注释来提供关于字符串的额外信息，这对于翻译人员理解上下文很有帮助。 12. **复数形式（Plural forms）** 不同的语言有不同的复数规则，`ngettext` 函数允许开发者指定复数形式的翻译规则。 13. **数据库应用程序** 在数据库应用中，本地化可能涉及数据库查询的文本或用户看到的错误消息，确保这些也得到适当的处理。 14. **防止不必要的翻译** 有时，有些字符串不应被翻译，比如硬编码的路径或内部变量名称。开发者需要确保这些不会被误提抽取出来。通过遵循这份说明书，开发者可以充分利用 GNU gettext 实现 Delphi、C++Builder 和 Kylix 应用程序的本地化，使其能适应全球不同地区的用户需求。

Chapter 2. Action

Application.Initialize;

Application.CreateForm(TForm1, Form1);

Application.Run;

end.

This works very, very well for most situations, but if you want translations to start as

early as possible, your .dpr ﬁle should look like this:

program Project1;

uses

gnugettext in ’gnugettext.pas’,

gginitializer in ’gginitializer.pas’,

Forms,

Unit1 in ’Unit1.pas’ {Form1};

{$R *.res}

begin

// Put ignores on the properties that cannot be translated

// These just have to be placed before the first call

// to TranslateComponents()

TP_GlobalIgnoreClassProperty (TMyComponent1,’property1’);

TP_GlobalIgnoreClassProperty (TMyComponent2,’property2’);

TP_GlobalIgnoreClassProperty (TMyComponent3,’property3’);

TP_GlobalIgnoreClassProperty (TMyComponent4,’property4’);

Application.Initialize;

Application.CreateForm(TForm1, Form1);

Application.Run;

end.

In this example, gginitializer sets all the necessary settings in gnugettext.pas. It

could look like this:

unit gginitializer;

interface

implementation

uses

gnugettext;

initialization

// Add extra domain for runtime library translations

AddDomainForResourceString (’delphi’);

// Force program to use Danish instead of the current Windows settings

UseLanguage (’da’);

// Do not put TP_GlobalIgnoreClass* statements here, because

// that would require this unit to use other units than gnugettext,

// and then all these units would have their initialization

// section executed before this one.

end.

In this example, the initialization section of gginitializer will be run before the initial-

ization sections of units like Forms and Unit1 are run.

Chapter 2. Action

Solving ambiguities

Sometimes it may happen that the same English message should be translated to two

different messages in another language. A very wellknown ambiguity is the word

"free", which can be like free beer or free speech. For instance, if you have two ra-

diobutton groups describing a piece of software, and the ﬁrst is about the software

price and the second is about the software type, both may include the choice "free".

The software price "free" would be translated to "gratis" in Danish, and the software

type "free" would be translated to "fri" in Danish.

It is the programmer’s responsibility to ensure, that one msgid only can result in

one translation. Sometimes this fails - and then the translator has to report back that

something has to be changed. There are several ways to solve this

Change words

The ﬁrst solution is to change the words. Instead of the price option "free" you could

give the option "$0", or you could write "free software" in one of the choices. Do a

brainstorm and pick the best.

Adding spaces

You could add a space to one of the strings. This would give the translations "free"-

>"fri" and "free "->"gratis". Spaces are not visible in a radiogroup. If you use this

technique inside the source code, you may want to remove the space before the space.

In this case, you should provide a comment to the translator that the space needs to

be preserved:

// Preserve the initial space in the translation.

dataset.FieldByName(’Name’).DisplayLabel:=copy(_(’ Name’),2,maxint);

A good translator should always preserve leading and trailing spaces, but sometimes

it is useful to give the translator a hint anyway.

Using domains

In some occasions, the solution to ambiguities can be to use several text domains. In

the case with two radio button groups, you would exclude one of them from Trans-

lateComponent() with TP_Ignore(), and then translate it separately afterwards us-

ing TranslateComponent(MyRadioButtonGroup,’separatedomain’);.

Using trailing comments

Some people using trailing comments to include a comment within the msgid:

function stripafterdot(s:widestring):widestring;

var

p:integer;

begin

p:=pos(’.’,s);

if p<>0 then

s:=copy(s,1,p-1);

Result:=s;

end;

myfield.DisplayLabel:=stripafterdot(_(’Name.Displaylabel for the field named "name"’));

This solution requires the translator to know about this notation.

Chapter 2. Action

Plural forms

The ngettext() function is a very powerful function for handling plural forms. In

order to understand this function, you should ﬁrst understand the gettext() func-

tion in the Section called function gettext(msg:widestring):widestring; in Appendix A>.

A well known problem is to specify the number of ﬁles in a list of ﬁlenames. With

this function, it can be done like this:

LabelCount.Caption:=format(ngettext(’%s file’,’%s files’,filelist.Count),[filelist.Count]);

If no translations are available, the ngettext() function will return ’%s ﬁle’

if ﬁlelist.Count=1, and it will return ’%s ﬁles’ otherwise. The format() function

will then put the actual number of ﬁles in place of the %s, and the result will be

something like ’0 ﬁles’, ’1 ﬁle’, ’2 ﬁles’, ’3 ﬁles’ etc.

If you would want to translate this to french, the entry in the po ﬁle should look like

this:

msgid "%s file"

msgid_plural "%s files"

msgstr[0] "%s fichier"

msgstr[1] "%s fichiers"

The idea with ngettext is, that it doesn’t just translate "%s ﬁle" to "%s ﬁchier", but it

takes into account, that the french use numbers differently. The English say "0 ﬁles",

but the french use singular to describe the value zero: "0 ﬁchier". So in the above

example, the french version would be: ’0 ﬁchier’, ’1 ﬁchier’, ’2 ﬁchiers’, ’3 ﬁchiers’...

Some languages are even more complicated. In Polish, there are three plural forms,

and the translation would look like this:

msgid "%s file"

msgid_plural "%s files"

msgstr[0] "%s plik"

msgstr[1] "%s pliki"

msgstr[2] "%s plikÃ

When counting ﬁles, it will become: ’0 plikÃ

w’, ’1 plik’, ’2 pliki’, ’3 pliki’, ’4 pliki’, ’5

plikÃ

w’. Confused? Don’t be. Just use ngettext() wherever your text depends on

a number, and the translator will provide the correct translations.

Not all tools handle msgid_plural well: Please note, that not all tools handle ms-

gid_plural well. This includes poEdit and KBabel. If a po ﬁle contains msgid_plural trans-

lations, you should use a text editor to edit it/translate. A good text editor for po ﬁles is

UniRed

How does it work?: The ngettext and dngettext functions use gettext(singular+#0+plural)

to get a #0-separated list of plural forms.

Because some tools don’t handle msgid_plural forms well, you should put all plural

forms translations into a separate po ﬁle. You can do this using dngettext(), which

is equivalent to ngettext() except that it takes a text domain name as ﬁrst parame-

ter:

LabelCount.Caption:=format(dngettext(’plurals’,’%s file’,’%s files’,filelist.Count),[filelist.Count]);

In this case, the source code string extraction will put the translation into a ﬁle

named plurals.po, and the dngettext() function will retrieve the translations

from plurals.mo. You can then ask the translator to use notepad to translate the

Chapter 2. Action

plurals.po ﬁle. Notepad is not always very handy, but it’s surely compatible with

the msgid_plural notation.

Database applications

Preventing unwanted translations

When you create a database application, there will be a lot of component properties

that you don’t want to be translated when using Translatecomponent(). Typically,

the ﬁeld names, table names and even database names of a database have meaningful

translations, and the translation ﬁle from the translator may include translations for

ﬁeld names. Also, SQL statements should not be translated. They will get extracted,

but if the translator modiﬁes them, it would most likely break your program if this

translation would be applied.

Therefore, it is very important, that you consult Appendix H> to see what ignores

you should add to your application. Make sure that these ignores are executed before

the ﬁrst call to TranslateComponent(). The list in that appendix may not be com-

plete - especially not if you use database components that are not mentioned. There-

fore you must have a look at your components and make sure, that all properties, that

should not be translated, have a corresponding TP_GlobalIgnoreClassProperty()

call.

DisplayLabel property explained

Delphi is very good for creating a single-language database application, fast, if the

application only needs one language. A typical single-language application uses ﬁeld

names that are easily understood, like "Name", "Address" etc. Let’s assume that you

use a query component with an SQL statement like this:

select * from customer order by Name

In this case, the name of the Name ﬁeld of the customer table will propagate through

all components, will become the column heading of a TDBGrid etc. Your grid column

for names will read "Name". This is desired in an English language application, but

absolutely not in all other languages.

The solution is to modify the .DisplayLabel property of the TField components,

that your dataset possesses. Every TDataset descendant has a .Fields[] property

that refers to the ﬁelds in the dataset, and all these ﬁeld components are descendants

of TField, which has the TField.DisplayLabel property.

Delphi provides two ways to modify this DisplayLabel property: At runtime and at

design time, which leads to two different ways of handling the localization of it.

Setting displaylabel at runtime

The runtime assignment solution is to assign a displaylabel at runtime like this:

procedure TForm1.Query1AfterOpen(DataSet: TDataSet);

begin

Dataset.FieldByName(’Name’).DisplayLabel:=_(’Name’);

end;

This way, the ﬁeld names are always the same in the database and the entire appli-

cation, but the user will see a localized name. This works for all dataset type compo-

nents, including table components, TClientDataset etc.

Chapter 2. Action

Display label at design time

Creating design-time DisplayLabel properties goes like this:

• Double-click the dataset component. This brings up the ﬁeld list window.

• Click with your right mouse button on the ﬁeld list window and choose "Add all

ﬁelds". This requires your dataset to be able to actually fetch data from the database

at design time, but will add all the ﬁelds of the dataset to the ﬁeld list window.

• Make sure that the form (or datamodule) that the dataset component is on, is trans-

lated using TranslateComponent() before the dataset is opened. This means that

the dataset needs to be closed by default, and that you have to open the dataset at

runtime using .Open or .Active:=True.

By doing this, the ﬁeld names will be present in the DFM ﬁles, and will therefore

be extracted for the translator to be translated. Now, TranslateComponent() will

translate the TField.DisplayLabel values:

procedure TForm1.FormCreate(Sender: TObject);

begin

TranslateComponent (self);

Query.Open;

end;

Multiple ﬁeld name translations

Sometimes it is very handy to have ﬁeld names translated to something else than

what you put into the .DisplayLabel property. For instance, you may want to have

a short version for exported ASCII ﬁles, another version for exporting XML ﬁles, one

version for reports, and again another version for the .DisplayLabel property.

This is easily done by using several po ﬁles (which is the same as multiple text do-

mains). The part of your program that writes a column header to an ascii ﬁle might

look like this:

write (mytextfile,dgettext(’fieldnames’,myfield.FieldName));

This will ﬁnd the ﬁeld name in the fieldnames.mo ﬁle and output the translation.

The fieldnames.po template can be written by hand (using notepad), or sometimes

be extracted from a datamodule. Often, the number of ﬁeld names is so low that the

quickest solution is to write the po ﬁle by hand.

Translation repositories

It is often very useful to create one po ﬁle that has all the translations from all other

po ﬁles included. For instance, if you are the producer of software for chemical lab-

oratories, and you have 5 different products, there will probably be a lot of common

translations for the different products, and it would save you a lot of work if you

don’t have to translate it all again for each new product.

In order to merge several po ﬁles, you can use the msgcat tool:

C:\translations\da>msgcat -o result.po -t utf-8 --use-first delphi7.po kylix3.po

C:\translations\da>

This set of parameters will put the result into result.po, use utf-8 encoding, and

only take the ﬁrst translation from each po ﬁle.

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