Slicer4:Internationalization of Slicer

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This pages contains notes on source code additions and modifications of different modules within Slicer for the internationalization purpose.

QT-based Internationalization

Internationalization is well supported in QT. A lot of modules of Slicer are developed on QT. This has set a good ground for the internationalization of Slicer.

  • basic idea

In Qt, tr() is one of the static public members of QObject class, which returns a translated version of input sourceText.

   QString QObject::tr ( const char * sourceText, const char * disambiguation = 0, int n = -1 ) [static]

tr() will search the translation in a so-called translation file. If nothing is found, then the sourceText instead of the translated version will be displayed directly. For example,

  • translation file template

The following is an example of the translation file, from English to Chinese.

   <?xml version="1.0" encoding="utf-8"?>
   <TS version="2.0" language="zh_CN">
Import Scene
Add Data

In the above example, all the texts are within the scope of qSlicerMainWindow class. So, 'qSlicerMainWindo' occurs in section 'name'.

  • The following modifications are are needed:

In file \Slicer4\Base\QTCore\qSlicerCoreApplication.h, add the following line:

   #include <QTranslator>

In file \Slicer4\Applications\SlicerQT\main.cxx (around line#230), add the following lines:

   static QTranslator* translator;
   if (translator != NULL)
       delete translator;
       translator = NULL;
   QString langCode= argv[1];
   translator = new QTranslator;
   QString qmFilename = "lang_" + langCode; 
   if (translator->load(qmFilename))
  • Prepare translation file

The translation file can be prepared manually based on the above template and file name extension should be like .ts, for example, lang_hz.ts, lang_de.hz, etc. Translation file can also be created conviently by a tool called lupdate. lupdate is a command line tool that finds the translatable strings (tr())in the specified source, header and Qt Designer interface files, and produces or updates .ts translation files. The following command will search the folder and subfolders for tr() occurences in files (.ui,.h,.cxx) and create translation file

      Usage: Lupdate c:\myproject\slicer4\ -ts   test.ts

  • To be continued

Scripted Module

Some modules are implemented in Python. Endoscopy is one of the typical examples. In, if we change the code in line#10

   parent.titel = “Endoscopy”


   parent.title =, "Endoscopy")

then "Endoscopy" can be shown in other languages.Similarily, other displayable strings can be handled in the same way.

To be continued