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use quote::quote;
#[proc_macro_derive(Vertex, attributes(vertex))]
pub fn vert(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let ast = syn::parse_macro_input!(input as syn::DeriveInput);
let ident = &ast.ident;
let fields = if let syn::Data::Struct(syn::DataStruct { fields, .. }) = &ast.data {
if let syn::Fields::Named(syn::FieldsNamed { named, .. }) = fields {
named
} else { unimplemented!("unnamed field") }
} else { unimplemented!("not struct") };
let attributed = fields.iter()
.filter_map(|f| {
let attr = f.attrs.iter()
.find(|a| {
a.path.segments.iter()
.find(|s| s.ident == "vertex")
.is_some()
});
match attr {
Some(a) => Some((f, a)),
None => None,
}
});
let attribute_descriptions = attributed
.map(|(f, attr)| {
let ident = f.ident.as_ref().unwrap();
let meta = attr.parse_meta().unwrap();
let location_nv = if let syn::Meta::List(p) = &meta {
p.nested.iter()
.find_map(|nm| {
if let syn::NestedMeta::Meta(m) = nm {
if let syn::Meta::NameValue(nv) = m {
match nv.path.segments.iter().any(|s| s.ident == "loc") {
true => Some(nv),
false => None,
}
} else { unimplemented!("not namevalue") }
} else { unimplemented!("not nested meta") }
})
.expect("no attr?")
} else { unreachable!() };
let location = if let syn::Lit::Int(i) = &location_nv.lit {
i
} else { unimplemented!("not int") };
let format_nv = if let syn::Meta::List(p) = &meta {
p.nested.iter()
.find_map(|nm| {
if let syn::NestedMeta::Meta(m) = nm {
if let syn::Meta::NameValue(nv) = m {
match nv.path.segments.iter().any(|s| s.ident == "format") {
true => Some(nv),
false => None,
}
} else { unimplemented!("not namevalue") }
} else { unimplemented!("not nested meta") }
})
.expect("no attr?")
} else { unreachable!() };
let format = if let syn::Lit::Str(s) = &format_nv.lit {
quote::format_ident!("{}", s.value())
} else { unimplemented!("not str") };
quote! {
plate::VertexAttributeDescription::new(0, #location, plate::memoffset::offset_of!(Self, #ident) as u32, plate::Format::#format)
}
});
quote! {
impl plate::VertexDescription for #ident {
fn binding_descriptions() -> Vec<plate::VertexBindingDescription> {
vec![
plate::VertexBindingDescription::new(0, std::mem::size_of::<Self>() as u32, plate::InputRate::VERTEX)
]
}
fn attribute_descriptions() -> Vec<plate::VertexAttributeDescription> {
vec![
#(#attribute_descriptions),*
]
}
}
}.into()
}
#[cfg(test)]
mod tests {
#[test]
fn it_works() {
let result = 2 + 2;
assert_eq!(result, 4);
}
}
