implement FieldData::clone()

[jacobmerson]

this adds an implementation to clone field data which is needed for
apf::convert to copy fields. closes #162

[wrtobin]

Do we want to commit to all copied fields being created as mesh tags?

Certainly all fields using the primary apf interfaces in apf.h are mesh tag fields but I'm not sure we want to have references to a subclass in a superclass. Should clone() be virtual and the type created depend on the subclass type?

[jacobmerson]

This is really up to you and @cwsmith. it was not pure virtual originally, so I just implemented it as that implied.

[wrtobin]

is this all whitespace changes?

If so revert these edits.

[jacobmerson]

This should be templated, so we don't have to use only a double field.

[wrtobin]

Why does this class need to be exposed? Is it used somewhere else in the commit?

[jacobmerson]

My mistake. I was using this in a previous attempt to get this working.

[jacobmerson]

@TobinW can you take another look at this. Some of my commits are a bit messy, so if under diff settings you change it to all commits rather than the last one you can see in sum what changed. If things look good to you I will squash all of my commits down into one.

[wrtobin]

Still need to remove these.

[wrtobin]

@Timetravellers This looks like a better approach to me, just need to remove a couple #include directives.

@cwsmith Anything jumping out at you? FieldData.h is non-public so changing the function to pure-virtual shouldn't break any downstream code and the only interface changes seems to be the additional function for UserData in apf.h

[jacobmerson]

@TobinW and @cwsmith updated and squashed. Let me know if there is anything else needed before merge.

[jacobmerson]

@TobinW I am finally done with this. We at least clone all mesh data that is used in tobinw/biotissue

[jacobmerson]

The one possibility where this breaks downstream code is if the user copies fields/tags etc. on their own. The downstream user no longer needs to copy fields when using apf::makeMdsMesh() or apf::convert().

[jacobmerson]

@cwsmith can you merge this? or are there more edits that need to be made?

[cwsmith]

I hit a compile error on pachisi using gcc 7.3.0

/lore/cwsmith/develop/core/apf/apfConvert.cc: In member function ‘void apf::Converter::convertTag(apf::Mesh*, apf::MeshTag*, apf::Mesh*, apf::MeshTag*)’:
/lore/cwsmith/develop/core/apf/apfConvert.cc:249:22: error: ‘cerr’ is not a member of ‘std’
                 std::cerr << "Tried to convert unknown tag type\n";
                      ^~~~
/lore/cwsmith/develop/core/apf/apfConvert.cc:249:22: note: suggested alternative: ‘errc’
                 std::cerr << "Tried to convert unknown tag type\n";
                      ^~~~
                      errc
/lore/cwsmith/develop/core/apf/apfConvert.cc: In member function ‘void apf::Converter::convertTags()’:
/lore/cwsmith/develop/core/apf/apfConvert.cc:331:20: error: ‘cerr’ is not a member of ‘std’
               std::cerr << "Tried to convert unknown tag type\n";
                    ^~~~
/lore/cwsmith/develop/core/apf/apfConvert.cc:331:20: note: suggested alternative: ‘errc’
               std::cerr << "Tried to convert unknown tag type\n";
                    ^~~~
                    errc
make[2]: *** [apf/CMakeFiles/apf.dir/apfConvert.cc.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [apf/CMakeFiles/apf.dir/all] Error 2
make: *** [all] Error 2

[jacobmerson]

@cwsmith see if that fixes the issue.