As we remove more and more virtual methods from VTK-m, I expect several
users will be interested in completely removing them from the build for
several reasons.
1. They may be compiling for hardware that does not support virtual
methods.
2. They may need to compile for CUDA but need shared libraries.
3. It should go a bit faster.
To enable this, a CMake option named `VTKm_NO_DEPRECATED_VIRTUAL` is
added. It defaults to `OFF`. But when it is `ON`, none of the code that
both uses virtuals and is deprecated will be built.
Currently, only `ArrayHandleVirtual` is deprecated, so the rest of the
virtual classes will still be built. As we move forward, more will be
removed until all virtual method functionality is removed.
The Visual Studio compiler has an annoying habit where if you use a
templated class or method with a deprecated class as a template
parameter, you will get a deprecation warning where that class is used
in the templated thing. Thus, if you want to suppress the warning, you
have to supress every instance of the template, not just where the
template is declared.
This is annoying behavior that is thankfully not replicated in other
compilers.
The implementation of `VariantArrayHandle` has been changed to be a
relatively trivial subclass of `UnknownArrayHandle`.
The advantage of this change is twofold. First, it removes
`VariantArrayHandle`'s dependence on `ArrayHandleVirtual`, which gets us
much closer to deprecating that class. Second, it ensures that
`UnknownArrayHandle` is a reasonable replacement for
`VariantArrayHandle`, so we can move forward with replacing that.
The Microsoft compiler has this annoying and stupid behavior where if
you have a generic templated method/function and that method is
instantiated with a deprecated class, then the compiler will issue a
C4996 warning even if the calling code is suppressing that warning
(because, for example, you are implementing other deprecated code and
the use is correct). There is no way around this other than suppressing
the warnings for all uses of the templated method.
We are moving to deprecate `ArrayHandleVirtual`, so we are removing the
feature where `VariantArrayHandle::CastAndCall` automatically casts to
an `ArrayHandleVirtual` if possible.
The big reason to make this change now (as opposed to later when
`ArrayHandleVirtual` is deprecated) is to improve compile times.
This prevents us from having to compile an extra code path using
`ArrayHandleVirtual`.
Many of the operations of `VariantArrayHandleBase` are not dependent on
the TypeList parameter of the class. Still others can operate just as
well by providing a type list to a method. Thus, it is convenient to
create a superclass that is not templated. That allows us to pass around
a `VariantArrayHandle` when the type list does not matter.
This superclass is called `VariantArrayHandleCommon` because "base" was
already taken.
This makes it clear that it returns true for an invalid array handle.
The previous name implied that it was looking for an ArrayHandle in some
"valid" set, which is the opposite.
Previously, the VariantArrayHandle::AsMultiplexer operation silently
failed and returned an invalid ArrayHandleMultiplexer. This is now
changed to throw an exception if the desired ArrayHandleMultiplexer
cannot hold the VariantArrayHandle's array.
Previously, the policy specified which field types the filter should
operate on. The filter could remove some types, but it was not able to
add any types.
This is backward. Instead, the filter should specify what types its
supports and the policy may cull out some of those.
Previously, the PolicyDefault used to compile all the filters was hard-
coded. The problem was that if any external project that depends on VTK-
m needs a different policy, it had to recompile everything in its own
translation units with a custom policy.
This change allows an external project provide a simple header file that
changes the type lists used in the default policy. That allows VTK-m to
compile the filters exactly as specified by the external project.
A new header named TypeList.h and the type lists have been redefined in
this new file. All the types have been renamed from `TypeListTag*` to
`TypeList*`. TypeListTag.h has been gutted to provide deprecated
versions of the old type list names.
There were also some other type lists that were changed from using the
old `ListTagBase` to the new `List`.
The newer List operations should still work on the old ListTags, so make
those changes first to ensure that everything still works as expected if
given an old ListTag.
Next step is to deprecate ListTagBase itself and move all the lists to
the new types.
Currently, ListTags are implemented by having a subtype name list set to
a brigand::list. However, there is always a chance this will change. To
make things more explicit, create a vtkm::internal::ListTagToBrigandList
to make it clear what the resulting type should be (and provide some
potential future-proofing).
Also add a convenient vtkm::ListTagApply that allows you to easily
instantiate a template with the list of types in a ListTag.
E.g:
```
ArrayHandle<Float64> doubleArray;
VariantArrayHandle varHandle{doubleArray};
ArrayHandleVirtual<Float32> = varHandle.AsVirtual<Float32>();
```
If there is a loss in range and/or precision, a warning is logged. If
the ValueTypes are Vecs with mismatched widths, an ErrorBadType is thrown.
Internally, an ArrayHandleCast is used between the VariantArrayHandle's
stored array and the ArrayHandleVirtual.
When you call VariantArrayHandle::CastAndCall, it now tries both basic
storage and virtual storage. You can modify the types of storages tried
by giving a type list of storage tags as the first argument.
ArrayHandleVirtual can automatically be constructed from any ArrayHandle.
In the cases where the input ArrayHandle doesn't derived from ArrayHandleVirtual,
it will automatically construct StorageAny to hold the array.
