Development/Languages/Smoke

Overview

SMOKE is a introspective wrapper around the Qt and KDE frameworks. Legend has it that SMOKE stands for Scripting Meta Object Kompiler Engine

Not only does it provide wrappers for every function in every class, but it also contains meta-information allowing queries of what functions are available and their arguments and return-types.

All classes, all methods, with all arguments, along with various flags reflecting staticness, virtuality, etc. are stored into cross-referencing arrays for fast lookups. One can thus read (and call) the whole Qt API by simply reading/searching these arrays.

The main purpose of SMOKE is to make it possible to write bindings from scripting languages to Qt and KDE - with an emphasis on ease of use and flexibility.

You can find out more about SMOKE by checking out the kdebindings module of KDE's SVN.

At the time of writing, the Perl bindings, Ruby bindings, C# bindings and PHP bindings are known to use it, you might find valuable usage information there.

Versions

While Smoke works like a charm for Qt3 and Qt4, a modular Smoke2 has been developed which makes it easy to wrap new C++ libraries and plug them together. The result is a noticeable list of technologies available to Smoke-based bindings, as Qt, QtUiTools, QtWebkit, Qtscript, Qscintilla, Qwt, Akonadi, Plasma, KDE, KDevPlatform, KHtml, KTextEditor, Nepomuk, Okular, Phonon, Solid, Soprano

Example

hello.cpp

include <smoke.h>
include <smoke/qt_smoke.h>

include <iostream>
include <string>
include <stdio.h>

using namespace std;
/*

* This class will intercept all virtual method calls and will get
* notified when an instance created by smoke gets destroyed.
*/

class MySmokeBinding : public SmokeBinding
{
public:
	MySmokeBinding(Smoke *s) : SmokeBinding(s) {}
	void deleted(Smoke::Index classId, void *obj) {
		printf("~%s (%p)\n", className(classId), obj);
	}
	bool callMethod(Smoke::Index method, void *obj,
		Smoke::Stack /*args*/, bool /*isAbstract*/)
	{
		Smoke::Method meth = smoke->methods[method];
		string name;
		// check for method flags
		if (meth.flags & Smoke::mf_protected) name += "protected ";
		if (meth.flags & Smoke::mf_const) name += "const ";
		// add the name
		name += smoke->methodNames[meth.name] + string("(");
		// iterate over the argument list and build up the
		// parameter names
		Smoke::Index *idx = smoke->argumentList + meth.args;
		while (*idx) {
			name += smoke->types[*idx].name;
			idx++;
			if (*idx) name += ", ";
		}
		name += ")";
		if (name == "protected mousePressEvent(QMouseEvent*)")
			cout << className(meth.classId) << "(" << obj
			     << ")::" << name << endl;
		return false;
	}
	/*
	 * In a bindings runtime, this should return the classname as used
	 * in the bindings language, e.g. Qt::Widget in Ruby or
	 * Qyoto.QWidget in C#
	 */
	char *className(Smoke::Index classId) {
		return (char*) smoke->classes[classId].className;
	}
};
// just for convenience, so we can pass Smoke::ModuleIndexes to std::cout
ostream& operator<<(ostream& lhs, Smoke::ModuleIndex rhs)
{
	lhs << "[" << rhs.smoke->moduleName() << ", " << rhs.index << "]";
	return lhs;
}
int main(int argc, char **argv)
{
	// init the Qt SMOKE runtime
	init_qt_Smoke();
	// create a SmokeBinding for the Qt SMOKE runtime
	MySmokeBinding binding(qt_Smoke);
	// find the 'QApplication' class
	Smoke::ModuleIndex classId = qt_Smoke->findClass("QApplication");
	/* find the methodId. we use a munged method signature, where 
	 * $ is a plain scalar
	 * # is an object
	 * ? is a non-scalar (reference to array or hash, undef) */
	Smoke::ModuleIndex methId = qt_Smoke->findMethod("QApplication",
		"QApplication$?");  // find the constructor
	cout << "QApplication classId: " << classId
	     << ", QApplication($?) methId: " << methId << endl;
	// get the Smoke::Class
	Smoke::Class klass = classId.smoke->classes[classId.index];
	// findMethod() returns an index into methodMaps, which has
	// information about the classId, methodNameId and methodId. we 
	// are interested in the methodId to get a Smoke::Method
	Smoke::Method meth = methId.smoke->methods[methId.smoke->methodMaps[methId.index].method];
	Smoke::StackItem stack[3];
	// QApplication expects a reference to argc, so we pass it as a pointer
	stack[1].s_voidp = &argc;
	stack[2].s_voidp = argv;
	// call the constructor, Smoke::Method::method is the methodId
	// specifically for this class.
	(*klass.classFn)(meth.method, 0, stack);
	// the zeroth element contains the return value, in this case the
	// QApplication instance
	void *qapp = stack[0].s_voidp;
	// method index 0 is always "set smoke binding" - needed for
	// virtual method callbacks etc.
	stack[1].s_voidp = &binding;
	(*klass.classFn)(0, qapp, stack);
	// create a widget
	classId = qt_Smoke->findClass("QWidget");
	methId = qt_Smoke->findMethod("QWidget", "QWidget");
	cout << "QWidget classId: " << classId
	     << ", QWidget() methId: " << methId << endl;
	klass = classId.smoke->classes[classId.index];
	meth = methId.smoke->methods[methId.smoke->methodMaps[methId.index].method];
	(*klass.classFn)(meth.method, 0, stack);
	void *widget = stack[0].s_voidp;
	// set the smoke binding
	stack[1].s_voidp = &binding;
	(*klass.classFn)(0, widget, stack);
	// show the widget
	methId = qt_Smoke->findMethod("QWidget", "show");
	cout << "QWidget classId: " << classId << ", show() methId: "
	     << methId << endl;
	meth = methId.smoke->methods[methId.smoke->methodMaps[methId.index].method];
	(*klass.classFn)(meth.method, widget, 0);
	// we don't even need findClass() when we use the classId provided
	// by the MethodMap
	methId = qt_Smoke->findMethod("QApplication", "exec");
	cout << "QApplication classId: " << qt_Smoke->methodMaps[methId.index].classId
	     << ", exec() methId: " << methId << endl;
	klass = methId.smoke->classes[methId.smoke->methodMaps[methId.index].classId];
	meth = methId.smoke->methods[methId.smoke->methodMaps[methId.index].method];
	// call QApplication::exec()
	(*klass.classFn)(meth.method, 0, stack);  
	// store the return value of QApplication::exec()
	int retval = stack[0].s_int;
	// destroy the QApplication instance
	methId = qt_Smoke->findMethod("QApplication", "~QApplication");
	cout << "QApplication classId: "
	     << qt_Smoke->methodMaps[methId.index].classId
	     << ", ~QApplication() methId: " << methId << endl;
	meth = methId.smoke->methods[methId.smoke->methodMaps[methId.index].method];
	(*klass.classFn)(meth.method, qapp, 0);
	// destroy the smoke instance
	delete qt_Smoke;

// return the previously stored value return retval; }

CMakeLists.txt

find_package(KDE4 REQUIRED)

include_directories(${KDE4_INCLUDE_DIR})
link_directories(${KDE4_LIB_DIR})

set(hello_src hello.cpp)
add_executable(hello ${hello_src})
target_link_libraries(hello smokeqt)

This assumes that you've installed KDE4 and kdebindings. If you only have SmokeQt installed, you need to adjust the paths accordingly.