Automatic Qt bindings: status update

["Mauro Iazzi" <mauro.iazzi@...>]

Hi all,
  I have changed much in my Qt bindings for Lua since last time I announced then, so here is a little status update. For a bunch of reasons, lqt has been rewritten from scratch, so it is actually a completely new binding generator.

As the previous version, this is not complete nor bug-free nor well tested. It is probably less feature-rich than the previous one. The main improvement, however, is that it no more depends on GCC-XML. This means that it should be a lot more portable than before.

The bindings are generated in two steps. A C++ parser (based on the one originally written by Roberto Raggi for KDevelop) parses any code which describes the API (a standard C++ header) and produces an XML description of it. Then a lua script generates the actual C++ code. This generated code defines wrappers for the functions that need one and subclasses that redefine virtual functions, so that Lua functions can be called as virtual members.

Actually, the generator does that for *any* function and class it finds, where possible (e.g. when those classes or functions are not private etc..). It can load filters that forbid to bind some of those functions or classes. However I put some effort in ensuring it only tries to bind what is actually public. Eventually, one should be able to feed it with a header and retrieve the binding as-is.

There is the possibility of specifying how some types are manipulated. For Qt bindings this means that QPoint and QRect are treated as 2 or 4 numbers respectively, and QByteArray is mapped into a normal string (QString is a userdata instead).

Enums are mapped into the corresponding strings. As another example of custom type definition, QFlags (a template which defines a bitmask of OR-ed enum values) are mapped into tables of these strings.

A special class is generated, which has one slot defined for each signal signature found. Whenever these slots are called, they call callbacks which can be defined from Lua.

All these features make the binding quite usable. Ihave been able to implement the first few tutorials from the Qt docs.
The latest snapshot can be downloaded from
http://repo.or.cz/w/lqt.git

Simple build instructions are included.

Possible future improvements, apart from polishing and documenting the code, may be generating SWIG or tolua++ interface files, so that the bindings rely on frameworks that are more stable and clean than the current one.

I hope someone is interested, comments and feedback are obviously welcome.
Cheers,

mauro