So far it contains just the uniform definitions and utilities related
to line drawing, nothing else, but especially the line utilities were
needed to be able to build MeshTools tests on a GL-less build.
This is unfortunately a breaking change to compileLines(), which now
takes the output of generateLines() instead of a line mesh. There's a
new assertion that'll blow up if the code is used the previous way,
sorry for the breakage.
What's however very useful about this change is that now it's possible
to take those generated line meshes and concatenate() them together,
achieving what's otherwise not implemented yet, such as drawing several
disconnected line strips or loops together.
It's all still partially private (the custom mesh attribute names are)
and I'm marking both APIs as experimental now to hint that it's not in
the final form/functionality yet. In particular, the data layout
optimizations described in the shader docs aren't used by these tools
yet, and if/once the line-specific vertex attributes become builtin,
compileLines() will not need to exist anymore as compile() will handle
that directly.
I still expect the API to change slightly to accomodate for line
stipple or textured lines (such as possibly having different smoothness
alongside and across the segment), plus there are some TODOs that might
change how it behaves in certain corner cases.
Currently just the bare minimum, more features such as handling
multiple contiguous strips and loops inside a single mesh or an
overlapping layout will come later.
The shader requires the input data to be laid out in a rather specific
way, and there will be a dedicated MeshTools utility for it in the
following commits. For independence though, the shader tests use a
custom helper.
The initial implementation has certain corner cases which will be
eventually resolved. For now they are pinned down with repro cases in
the test. But apart from that, it's pretty much usable in practice.
Remaining join styles (round and miter-clip) as well as stipple support
will eventually follow as well.
Vladimír Vondruš