Multilingual support for applications

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• Download example application - 43.7 Kb

Why another article about multilingual applications?

Well, about a year ago, I needed my application to support multiple languages. I thought it would be very easy to find out how to do this. There are a lot of articles that explain how to do this, but none of them fit my needs.

What can I find here?

• Introduction
• How to use?
• Supported languages
• History

Introduction

What I really needed were simple .h and .cpp files which are able to load a language DLL and extract the strings I need. None of the articles I found provided this. At this point, I decided to write my own classes which could do the task I wanted them to do. I am a little active on some forums, and I see this question keeps coming back of how to implement multiple languages to an application. What I see is that it is really hard to understand how it works, the first time. So I decided to write a little article and add my language files to CodeProject.

How to use?

I tried to implement the files so that they are really easy to use. Let's explain how the class works.

Use string tables

Some people are still hard-coding the strings of their application in their code. This isn't the best solution on earth. So use string tables, because this is needed if you want to add multiple language support to your application.

Add files to project

First of all, you have to add the files Language.cpp and Language.h to your project. Now you are almost ready adding multilingual support to your application. The class I developed is a so-called singleton class. This means that you don't have to create the class every time. You only have to load and release the language at startup, and you can use the class everywhere.

How to load a language

Now, you are ready to load your first language. Normally, you load language at the startup of your application. Here is some example code that will try to load the system's default language:

BOOL CMyApp::InitInstance()
{
    .. some default code here

    // Init language object 
    CLanguage * pLanguage = CLanguage::Instance(); 

    // If you want, you can init the location of the dll's and the default language
    pLanguage->Init("lng", "dutch");

    // Load system default language 
    if (!pLanguage->LoadLanguage(GetSystemDefaultLangID())) 
    { 
        // Show error
        AfxMessageBox("Unable to load system language, "
                                  "default language is used");
    }

    // Load dialog
    CMyDialog dlg;
    dlg.DoModal();
    
    // Release language
    pLanguage->ReleaseLanguage();

    .. rest of code
}

It was pretty easy to load a language, wasn't it? Keep in mind that the Init function is not really needed. If you don't call this function, the defaults "lng" and "english" are used. But this is not all, you also have to load the strings.

How to load strings

You have loaded a language, but you also want to load strings. For example, you have a dialog with a nice static control. This is how you load the language:

BOOL CMyDialog::OnInitDialog()
{
    // Call original function
    CDialog::OnInitDialog();

    // Init language object
    CLanguage * pLanguage = CLanguage::Instance();

    // Set text for static control
    m_lblMyStatic.SetWindowText(pLanguage->GetString(IDS_MYSTATICTEXT).c_str());

    .. rest of code
}

The language object will see if the user has loaded a valid DLL. If so, the string will be loaded from the DLL, if not, the default string table will be used. Still easy isn't it? That is all you have to do in your application.

How to create the language DLLs

There are a few easy steps to take:

1. Create project.

   First, you have to create a project for your DLL. Start Visual Studio, and choose File -> New.... Then select Win32 Dynamic-Link Library. Give your project a new name and click OK. You now have seen a wizard, select a DLL that exports some symbols. The default files for the DLL are now created.

2. Copy string table from original project.

   Now the default files are created, close the current (language DLL) project. Open your real application in the IDE now and open the string table. Use CTRL + A to select all items and then copy them. Close project again.

3. Add string table to language project.

   Open your language project again. Select File -> New... and select resource script. Give the resource script a name and click OK. Now you can add resources to your project. Right click on the resource file and select Insert..., then select String table. Now copy the string table of your application to the language DLL (just use CTRL + V). As you will see, all values are now in the language DLL. You can start translating all the sentences now. If you are ready, you can compile the project. The DLL is now ready to use!

Languages

There are a lot of languages automatically supported by the language class. Of course, you can edit these settings yourself in Language.cpp (see InitLanguages function). A list of languages supported and the name of the DLL which is expected is given below:

History

• June 3^rd, 2005
  • Updated source code, constants can be changed at run-time;
  • Updated source code, you don't have to link to libraries anymore;
  • Removed MFC version, Win32 version will work in MFC applications;
• June 1^st, 2005
  • Added example application;
  • Added MFC and non-MFC versions;
  • Fixed bug when including multiple files;
• May 26^th, 2005
  • First release.

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