Typical way of formatting user visible strings in application interfaces, for a long time has been that of plain text or at most visual markup like HTML tags. In most textual content environments, shift to semantic markup has been recognized as superior to visual (for example, the Docbook XML for documentation). Why not go down the same road for UI strings?
In the semantic model, user interface strings are marked for their context, and text elements within for their meaning rather than visual appearance. Consider few i18n examples of usual, non-semantic format:
KDE TechBase i18n("Move");
i18n("Descending");
i18n("<qt><b>%1</b> does not exist</qt>", fname);
i18n("<h1>History Sidebar</h1> You can configure the history sidebar here.");
Using KDE UI Text (KUIT for short) semantic markup, these strings would be formated like this:
i18nc("@action:button", "Move");
i18nc("@item:inmenu", "Descending");
i18nc("@info", "<filename>%1</filename> does not exist", fname);
i18nc("@info:whatsthis",
"<title>History Sidebar</title>"
"<para>You can configure the history sidebar here.</para>");
Two distinct differences between ordinary and KUIT markup can be observed.
The first is the use of context i18n calls, the i18nc(), to convey the usage context of the string by means of the context marker. The first message above, "Move", has been assigned the @action:button marker, where @action is the semantic role which describes the text as an action to be taken (e.g. operation on data or opening of a new dialog), and :button is the interface subcue saying that this text is displayed on a pushbutton widget. The second message, "Descending", has been marked as semantically a list item (@item), displayed in a menu (:inmenu). The interface subcue can be left out if none is appropriate, as has been done in the third message.
The other difference is the use of the semantic tags, which convey the meaning of a word or phrase within the text. The <filename>%1</filename> part of the third message tells that the substituted text is the name of a file. The <title> and <para> tags in the last message clearly lay out structure of a longer informational text.
| Note |
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The context marker can be added when within some of the standard XML sources too. In Qt Designer forms (.ui files), each text label to a widget has comment attribute (presented as "disambiguation" property within Designer, or "comment" prior to Qt 4.5), which can be used in the same manner as context argument of i18nc() call. Similarly, in the KXmlGui (.rc) and KConfigXT (.kcfg) files, tags <text>, label, and whatsthis can have a context attribute. For example:
<label context="@label">Hide trivial details</label>
<whatsthis context="@info:whatsthis">Option to hide drivel</whatsthis>
<text context="@item:inmenu">&New...</text>
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Even when a context marker is present, sometimes the programmer may want to provide an additional "free-form" description to translators, in order to shed more light on particularly ambiguous strings. The free-form description is just separated by a whitespace from the context marker proper, like this:
i18nc("@item:inmenu Sorting order", "Descending");
One particularly useful and yet general piece of free-form description, is the title under which the message is grouped -- the menu title for actions in menu, the group title of set of radio-buttons, the listbox label for items in list, etc. For example:
iconSizeBox = new QGroupBox(i18nc("@title:group", "Icon Size"), this);
//...
iconSize1 = new QRadioButton(i18nc("@option:radio Icon Size", "Small"), this);
iconSize2 = new QRadioButton(i18nc("@option:radio Icon Size", "Medium"), this);
iconSize3 = new QRadioButton(i18nc("@option:radio Icon Size", "Large"), this);
//...
KUIT markup has advantages both to users and to translators of applications that make use of it.
For the users, the use of semantic tags means consistent formatting of same kinds of text. A notorious example of inconsistent visual formatting are filenames and paths, which are sometimes put in as is, sometimes in quotes (and ordinary quotes at that, rather than proper English fancy quotes), and sometimes in bold tags. Furthermore, the text within the tag may be modified when semantically marked; for example, the standard "/" path delimiters in a <filename> text will be substituted for platform specific ones.
Translators will benefit from both context markers and tags. For the @action role of the "Move" string in the example above, the translator may use command form of the verb, while gerund form (like "Moving") may be more appropriate for the @title role, which would be used if the string was title of the menu, window, etc. The interface subcue, like :button above, if present, additionally enables the translator to mentally picture the actual runtime GUI. Tags within the text will also benefit translators, as they may clarify the structure of the sentence, especially in presence of placeholder substitutions.
Context markers also serve a technical purpose: they decide whether what form of visual formatting is used. For example, any @title role will use plain text, whereas @info will frequently produce rich text, depending on the subcue.
None the least, semantic markup removes the burden from programmers of thinking about the visual formatting to apply, like "Should I put the path in quotes or <b>?", or "Should the title be <h2> or <h3>?", and so on.
Context marker consist of the semantic role and the interface subcue, in the form of @role:subcue. Each message should be given a role, but the subcue may be left out. The subcue should be given only when the string clearly maps to the user interface element that it describes.
Every role/subcue combination determines the default visual formatting of resulting string, whether it comes out as plain or rich text. See the section on limitations for a way to override the default formatting when necessary.
| Warning |
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| Roles and subcues in the context marker cannot be specified at will, but must be drawn from the sets defined below. This is important for several reasons, one being that translators have deliberated about and agreed upon the meanings of presented sets, rather than having to second-guess arbitrary combinations. |
KUIT defines the following roles and subcues (with notes on default visual formatting):
KUIT semantic tags come in several logical groups:
Phrase tags will by default not admit any subtags; where some subtags can be used, it is so indicated. KUIT defines the folowing phrase tags:
i18nc("@action:inmenu",
"Open with <application>%1</application>", appName);
i18nc("@info:whatsthis",
"You can try the following snippet:<bcode>"
"\\begin{equation}"
" C_{x_i} = \\frac{C_z^2}{e \\pi \\lambda}"
"\\end{equation}"
"</bcode>");
i18nc("@info",
"This will call <command>%1</command> internally.", cmdName);
i18nc("@info",
"Consult man entry for <command section='1'>%1</command>", cmdName);
i18nc("@info",
"Send bug reports to <email>%1</email>.", emailNull);
i18nc("@info",
"Send praises to <email address='%1'>the author</email>.", emailMy);
i18nc("@info:progress",
"Checking <emphasis>feedback</emphasis> circuits...");
i18nc("@info",
"Assure that your <envar>PATH</envar> is properly set.");
i18nc("@info", "Cannot read <filename>%1</filename>.", filename);
i18nc("@info",
"<filename><envar>HOME</envar>/.foorc</filename> does not exist.");
i18nc("@info:tooltip",
"Execute <icode>svn merge</icode> on selected revisions.");
i18nc("@info:whatsthis",
"If you make a mistake, click "
"<interface>Reset</interface> to start again.");
i18nc("@info:whatsthis",
"The line colors can be changed under "
"<interface>Settings->Visuals</interface>.");
i18nc("@info:tooltip",
"Go to <link>%1</link> website.", urlKDE);
i18nc("@info:tooltip",
"Go to <link url='%1'>the KDE website</link>.", urlKDE);
i18nc("@info",
"The fortune cookie says: <message>%1</message>", trouble);
i18nc("@info",
"Do you really want to delete:<nl/>"
"<filename>%1</filename>", fileName);
i18nc("@info:progress",
"Connecting to <numid>%1</numid>...", portNo);
i18nc("@info",
"Replace <placeholder>name</placeholder> with your name.");
i18nc("@item:inlistbox",
"<placeholder>All images</placeholder>");
i18nc("@info", "Apply color scheme <resource>%1</resource>?", colScheme);
i18nc("@info:whatsthis",
"Cycle through layouts using <shortcut>Alt+Space</shortcut>.");
Sentence tags mark complete sentences in text, and will admit any phrase tags as subtags. The following are defined:
i18nc("@info",
"Probably the best known of all duck species is the Mallard. "
"It breeds throughout the temperate areas around the world. "
"<note>Most domestic ducks are derived from Mallard.</note>");
i18nc("@info",
"Really delete this key?"
"<warning>This cannot be undone.</warning>");
Structure tags are used to split longer texts into titles, paragraphs, and lists. By default they can contain any phrase or sentence tags, unless indicated otherwise.
If any of the structure tags is present, then there must be no text outside of structure tags. The following is not valid KUIT markup:
// invalid markup
i18nc("@info",
"<title>History Sidebar</title>"
"You can configure the history sidebar here."); // <para> missing
Semantic markup cannot be used in "dumb" strings, which do not pass through KDE's i18n subsystem. These would be, for example, strings in .desktop format files. But not the strings in UI files, as in Qt Designer they can be equipped with both context markers (via comment field to text properties) and semantic tags.
Qt's rich text HTML tags can be used concurrently with KUIT tags, but this is not advised unless necessary. They may be needed, for example, to create tables or insert images, as KUIT does not implement this functionality at the moment.
Sometimes, the visual formatting may not be quite appropriate for the output device; every role/subcue combination has a preset default formatting. For example, if the @info role is applied to a string which is used in a widget that does not handle rich text, it will come out with HTML tags displayed verbatim. To handle this, visual formatting can be explicitly signaled by /format modifier appended to context marker:
i18nc("@info/plain",
"<filename>%1</filename> does not exist", fname);
Presently, the possible format modifiers are /plain, /rich and /term (for terminal format, possible use of escape sequences).
To specify context in kpartgui rc file use context attribute (<text context="@title:menu">File</text>). A context-aware version of I18N_NOOP is I18N_NOOP2.
Admittedly, KUIT markup is an additional thing to be learned and applied throughout the course of development. By now you may be wondering if it is worthwile to invest time into that, particularly in view of two cases:
You are strongly advised to use KUIT for new code. Compared to the total time spent on code, writing UI messages is only a small fraction. Context markers will help translators a lot, and message tags will provide consistent visual text formatting to your application.
When modifying existing code, there are two issues. First, obviously it is a daunting task to go through hundreds (or worse) of messages and equip them with semantic markup. Second, by changing the messages, the translators too will have to review their existing translations; however, it is not expected that the porting will take so "epic" proportions that the translators cannot keep up. Sumarily, feel free to do as you see fit.
Additionally, for porting, keep in mind that it is not all-or-nothing proposal. Any amount of semantic messages are useful to translators, and users can only see the difference for the better. Thus, for example, deciding to make all new messages semantic and slowly over time fix old messages, is a perfectly fine strategy.
To make your job easier, there is an i18n-checker script that will report the problems in KUIT markup, as well as check some other i18n nuances. It is run daily on KDE code repository-wide as part Krazy-framework, but you can also run it locally on your code. It can be found in trunk/quality/krazy2/plugins/general/i18ncheckarg. Furthermore, as of this moment Krazy checks only C++ sources, while when you run the script locally, some of the XML sources containing translatable strings will be checked as well. i18ncheckarg requires Perl libxml bindings, which are probably already packaged for your distribution (Debian package is libxml-libxml-perl).
| Note |
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| By default i18ncheckarg takes a single filename to check, but using --allsources option you can provide as many file or directory paths as you wish; typically you would give top directory path to your sources. Also, to report all missing context markers use --ctxmark option, or otherwise missing markers will be reported only if some threshold of marked-to-total number of messages in a file is reached. |
Last but not the least, there is also a chic-effect to the KUIT. Its wide use, together with some under-the-hood elements on translators' disposal, will make KDE4's i18n layer without peer in free or proprietary software world. Insofar as you consider localization excellence an important part of the overall KDE excellence, this is something that may also tip your decision :) -- Your Friendly Translator.
