Support reading VTK version 0.1 files

[halleysfifthinc]

I have some version="0.1" .vtp files that error on reading at this line

ReadVTK.jl/src/ReadVTK.jl

Line 115 in 045a603

header_type = attribute(root, "header_type", required = true)

From the VTK XML wiki

The header-type specified may be either "UInt32" or "UInt64" and indicates the integer type used in binary data headers (see below). If no such attribute is specified (as in version 0.1) the header type is UInt32.

So requiring "header_type" to be present should be predicated on the version number (if you want to support VTK XML version 0.1).

I am working around this by adding that attribute to the files I'm trying to read, but that is only feasible because I am only reading 3 files.

EDIT: That doesn't work because header_type is assert required to be UInt64 here

ReadVTK.jl/src/ReadVTK.jl

Line 134 in 045a603

@assert header_type == "UInt64"

[ranocha]

Please feel free to make a PR generalizing the code and adding appropriate tests.

[halleysfifthinc]

👍 Not something I need enough to make a PR, but wanted to open the issue so that it would be known.

It would be nice to note the minimum VTK XML version in the README if this isn't planned or a priority.

[ranocha]

We will only implement what we need for ourselves, but we will be happy to review contributions.

[sloede]

It would be nice to note the minimum VTK XML version

IIRC from a conversation with some folks at Kitware, there is no versioned documentation of the VTK XML file format. That is, it is not documented which format version supports which features/structures - rather, it is implicit by following what the reference VTK implementation supports. Thus I am not sure if it would really help to attach something like this to VTK XML.

It seems to be different for the new VTK HDF format though: https://docs.vtk.org/en/latest/design_documents/VTKFileFormats.html#vtkhdf-file-format