There was a warning comes from the functors in support of the portals
for ArrayHandleMultiplexer. The template has no good way to determine
whether the object it is calling is for control or execution, so it
supports both. It is not useful to warn when it happens to compile only
for the host.
This is done through a new version of ApplyPolicy. This version takes
a type of the array as its first template argument, which must be
specified.
This requires having a list of potential storage to try. It will use
that to construct an ArrayHandleMultiplexer containing all potential
types. This list of storages comes from the policy. A StorageList
item was added to the policy.
Types are automatically converted. So if you ask for a vtkm::Float64 and
field contains a vtkm::Float32, it will the array wrapped in an
ArrayHandleCast to give the expected type.
There was a special case for ArrayHandleMultiplexer where if you gave it
just one type it would treat that as a value type rather than an array
to support and instead provide a default list of types. However, GCC 4.8
is having trouble compiling the code to create the default list, the
semantics are confusing, and the more I think about it the less likely I
think we will need this functionality. So, just getting rid of that.
The code was working fine on all the dashboards except for the Visual
Studio 2015 compiles on delve. It gave an error like:
ArrayHandleMultiplexer.h(398): error C2938: 'ArrayHandleToStorageTag<unknown-type>' : Failed to specialize alias template
A StackOverflow article (https://stackoverflow.com/questions/43411542/
metaprogramming-failed-to-specialize-alias-template) suggests that this
is a bug in older versions of Visual Studio. Although fixed in more
recent versions, we might have to support older versions.
