Translations: Start documentation for translations.

doxygen/translation.dox

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+/**
+
+@page translation Translations / Internationalization
+
+@section lang-available Available Languages
+
+The development, documentation and default application language of gds-render is English.
+Translations of GUI and console output exist for the following locales/languages
+
+- de German (Deutsch)
+- ja Japanese (日本語) (Work in progess)
+
+On how to add new languages, see @ref lang-add
+
+@section lang-internals Internals
+This progamm uses gettext for translations.
+
+@subsection lang-coding Make Strings Translatable in Code
+Only strings, that are marked as translatable are actually available for translation and shown in the user's language.
+All other text is displayed as written in the source files.
+
+@subsubsection lang-add-glade Make GUI Elements in Glade Files Translatable
+Text inside Glade's GUI files can be made translatable by checking the *translatable* option for the specific text property.
+The following image shows the label property of a button. Notice the checked Translatable option.
+@image html translate-glade.png
+@image latex translate-glade.png
+
+@subsubsection lang-add-c Make C Strings Translatable
+In order to make strings in C code translatable, the following header has to be included:
+@code
+#inlcude <glib/gi18n.h>
+@endcode
+This header provides a few macros useful for translation. The most important one is the function-like macro
+@code
+_("Text here")
+@endcode
+which is just a underline character.
+You can use this marco to encapsulate all static strings that shall be translated. The whole expression is still usable like any other string (except for compile time concatenation, like: "This is foo" " and this is bar")
+
+Example:
+@code
+printf(_("The value of foo is %d\n"), foo);
+@endcode
+
+Text that must not be translated can be encapsulated inside a N_ macro like
+@code
+N_("This has to stay in English")
+@endcode
+The N_ macro is basically an empty macro and just for visualization.
+
+@subsection lang-add Add a New Language
+
+*/