XSL-T and Qt

A couple of weeks ago, I merged the development branch for XSL-T into our main line, heading for Qt 4.5. The idea is that Qt will carry an XSL-T 2.0 implementation with as usual being cross-platform, having solid documentation, and easy of use.

Using it is should straightforward. Either on the command line:

xmlpatterns yourStylesheet.xsl yourInputDocument -param myParam=myValue

Or using the C++ API[1]:

QXmlQuery myQuery(QXmlQuery::XSLT20);
myQuery.bindVariable("myParam", QVariant("myValue");
myQuery.setQuery("http://example.com/myStylesheet.xsl");
QFile out("outFile.xml");
out.open(QIODevice::WriteOnly);

myQuery.evaluateTo(&out);

See the documentation for the QXmlQuery class on the overloads available for setQuery() and evaluateTo(), for instance.

However, due to the beast XSL-T 2.0 is — I agree that it’s larger than XQuery — we’ve decided to do this according to the “release early release often” approach. The first, in Qt 4.5, will carry a subset, and subsequently be complemented in Qt 4.6. The current status is documented in the main page for the QtXmlPatterns module, which can be viewed in the documentation snapshot.

Therefore, while the current implementation probably falls short on more complex applications(such as Docbook XSL), it can run simpler things, users can plan ahead, and we trolls can receive feedback on what features/APIs that are missing, and what needs focus. So feel free to do that: send a mail to qt-bugs@trolltech.com, or say hello on IRC(FransE, on Free Node).

The code is accessible through the Qt snapshots.

What is XSL-T anyway?

XSL-T is a programming language for transforming XML into XML, HTML or text. Some implementations,  such as QtXmlPatterns or Saxon, provides mechanisms to map XML to other data sources and hence widens the scope of the language by letting the XML act as an abstract interface. Wikipedia has a good article on XSL-T. Version 2.0 of XSL-T extends the language heavily by putting a rigid type system and data model in the backbone, and adds many features that was a pain to miss when programming in XSL-T 1.0. XSL-T 2.0 use XPath 2.0, and shares the same large function library as XQuery.

1.

Over time, Java bindings through QtJambi and ECMAScript bindings through QtScript, will likely arrive.