Revamp the OCCT Handle

Hello everyone,

Here is the status on the Handle Revamping task's.

As explained before we decided to go with the C++11 implementation.
In the same process, I started to remove the persistent classes.

Note that I'm working on Linux with gcc version 4.4.1.

1) I defined a class handle which inherits from std::shared_ptr<T>.
In this class, I implemented the methods specific to Handle_Standard_Transient, like IsNull, by using equivalent methods of std::shared_ptr<T>.
I also added constructors and operators to be able to convert a handle<B> to handle<A>, when B inherits from A.

------
#include <tr1/memory>

template <class T>
class handle : public std::tr1::shared_ptr<T>
{
handle() : std::shared_ptr<T>() {}
template<class U> handle(const handle<U>& h) : std::shared_ptr<T>((T*)h.get()) {}
handle(const T* t) : std::shared_ptr<T>((T*)t) {}

template------

This handle class being defined into the new occ namespace, the Handle() macro is redefined as follows:
------
#define Handle(ClassName) occ::handle<ClassName>
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2) I then redefined some macros in Standard_DefineHandle.hxx as follows:
Replacement of DEFINE_STANDARD_HANDLE, which defines the full Handle class, by a simple typedef.
Nullification of the IMPLEMENT_DOWNCAST macro, which was implementing the DownCast method - it is no more usefull since the method is fully implemented in the class.

------
DEFINE_STANDARD_HANDLE(C1,C2)
class C1; \
Standard_EXPORT const Handle(Standard_Type)& STANDARD_TYPE(C1); \
typedef handle<C1> Handle_##C1;

#define IMPLEMENT_DOWNCAST(C1,BC)
------

3) Based on this implementation, some changes in existing sources are required:
* I had to fix some typo in the usage of the Handle macro (due to the new definition)

Example:
------
Handle(Draw_Drawable3D()) --> Handle(Draw_Drawable3D)()
const Handle(Geom_Surface&) --> const Handle(Geom_Surface)&
Handle(Geom_Surface::DownCast()) --> Handle(Geom_Surface)::DownCast()
------

* The forward declarations of Handle classes also had to be removed or just replaced by a forward declaration of the class.

Example:
------
class Handle_Geom_Surface; // Handle_Geom_Surface is a typedef
class Handle(Geom_Surface); // Handle(Geom_Surface) is a macro for occ::handle<>
------

* The main issue is with out parameter of handle type.
When the type of a out parameter is a handle the compiler produces an error.

Example:
------
Class A {};
Class B : public A {}

void foo(Handle(A)& outParam)
{
outParam = new B();
}

void bar()
{
Handle(B) b;
foo(b); // compilation error
}
------

There are different ways to fix this.
First, in some cases, we can use a Handle(A) instead of a Handle(B) because, in the rest of the code, nothing about the specialization of B is needed.

Another way, is to cast the Handle(B) into a Handle(A).
This can be done like this:
------
foo(*(Handle(A)*)&b)

// or with a macro
#define super_cast(CL) *(Handle_##CL*)&
foo(super_cast(A)b);
------

This concerns few methods but some of them are widely used, such as:
------
TDF_Label::FindAttribute(..., Handle(TDF_Attribute)&)
IGESData_ParamReader::ReadEntity(..., Handle(IGESData_IGESEntity)&, ...)
------

Which are usually called with derived classes parameters.

4) Currently I built most of the packages and the remaining ones have more to do with the removal of the persistent classes.
I hope to be able to build DRAWEXE soon, so that I can launch the test suits.

If the tests go well, the next step will be to change the way WOK generates the files to get rid of the Handle_X.hxx files.

FrГ©dГ©ric