Cross-Platform GUI Programming with wxWidgets

When taking your application to an international market, the first thing that comes to mind is translation. You will need to provide a set of translations for all the strings your application presents in each foreign language that it supports. In wxWidgets, you do this by providing message catalogs and loading them through the wxLocale class. This technique may differ from how you are used to implementing translations if you currently use string tables. Instead of referring to each string by an identifier and switching tables, message catalogs work by translating a string using an appropriate catalog. (Alternatively, you can use your own system for handling translations if you prefer, but be aware that messages in the wxWidgets library itself rely on catalogs.)

Without message catalogs, the untranslated strings in the source code will be used to display text in menus, buttons, and so on. If your own language contains non-ASCII characters, such as accents, you will need a separate "translation" (message catalog) for it because source code should only contain ASCII.

Representing text in a different language can also involve different character encodings, which means that the same byte value might represent different characters when displayed on-screen. You need to make sure that your application can correctly set up the character encodings used by your GUI elements and in your data files. You need to be aware of the specific encoding used in each case and how to translate between encodings.

Another aspect of internationalization is formatting for numbers, date, and time. Note that formatting can be different even for the same language. For example, the number represented in English by 1,234.56 is represented as 1.234,56 in Germany and as 1'234.56 in the German-speaking part of Switzerland. In the USA, the 10th of November is represented as 11/10, whereas the same date for a reader in the UK means the 11th of October. We'll see shortly how wxWidgets can help here.

Translated strings are longer than their English counterpart, which means that the window layout must adapt to different sizes. Sizers are best suited to solve this part and are explained in Chapter 7, "Window Layout Using Sizers." Another layout problem is that for Western languages, the flow of reading goes from left to right, but other languages such as Arabic and Hebrew are read from right to left (called RTL), which means that the entire layout must change orientation. There is currently no specific mechanism for implementing RTL layout in wxWidgets.

The last group of elements to be adapted to a different language or culture consists of images and sounds. For example, if you are writing a phone directory application, you might have a feature that speaks the numbers, which will be language-dependent, and you might want to display different images depending on the country.