1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147

#![recursion_limit = "128"]
#![deny(warnings)]
extern crate proc_macro;

use std::collections::HashSet;

use proc_macro2::TokenStream;
use quote::quote;
use syn::{parse_macro_input, spanned::Spanned, Attribute, Data, DeriveInput, Fields, Ident};

use error::Error;

use crate::error::ErrorKind;

mod error;
mod parser;

#[proc_macro_derive(Gui, attributes(imgui))]
pub fn ui_derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let input = parse_macro_input!(input as DeriveInput);
    match impl_derive(&input) {
        Ok(output) => output.into(),
        Err(error) => error.to_compile_error().into(),
    }
}

fn impl_derive(input: &DeriveInput) -> Result<TokenStream, Error> {
    let name = &input.ident;
    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();

    let (body, catch_fields, catch_methods) = match input.data {
        Data::Struct(ref body) => struct_body(body.fields.clone()),
        _ => Err(Error::non_struct(input.span())),
    }?;

    // crate a new type.
    // It should never generate a collision
    let event_type = Ident::new(&format!("__{}_Events", name.to_string()), input.span());

    Ok(quote! {
        #[allow(non_camel_case_types)]
        pub struct #event_type {
            #catch_fields
        }
        impl #event_type {
            #catch_methods
        }
        impl #impl_generics imgui_ext::Gui for #name #ty_generics #where_clause {
            type Events = #event_type;
            fn draw_gui(ui: &imgui::Ui, ext: &mut Self) -> Self::Events {
                // Because all fields are bool, it should be OK to zero the memory (right...?)
                let mut events: Self::Events = unsafe { std::mem::zeroed() };
                #body
                events
            }
        }
    })
}

/// Adds support to allow multiple imgui tags in a single field:
/// ```
/// struct Demo {
///     #[imgui(drag(...))]
///     x: f32,
///
///     // multiple annotations
///     #[imgui(separator)]
///     #[imgui(slider(...))]
///     #[imgui(input(...))]
///     y: f32,
/// }
fn struct_body(fields: Fields) -> Result<(TokenStream, TokenStream, TokenStream), Error> {
    let mut input_methods: TokenStream = TokenStream::new();

    let mut input_fields: TokenStream = TokenStream::new();
    let mut input_fields_set = HashSet::new();

    let field_body = fields
        .iter()
        .enumerate()
        .flat_map(|(_, field)| {
            // TODO support for unnamed attributes
            let ident = field
                .ident
                .clone()
                .expect("Unnamed fields not yet supported.");
            let ty = &field.ty;

            // collect all the imgui attributes
            // we need to check that there is only one.
            let attrs: Vec<Attribute> = field
                .attrs
                .iter()
                .filter(|attr| {
                    let ident = Ident::new("imgui", attr.span());
                    attr.path.is_ident(&ident)
                })
                .cloned()
                .collect();

            let mut attrs = attrs.into_iter();
            let first = attrs.next();
            let second = attrs.next();

            match (first, second) {
                // No annotations were found.
                // Emmit no sourcecode.
                (None, None) => vec![Ok(TokenStream::new())],

                // There is more than one imgui annotation.
                // Raise a descriptive error pointing to the extra annotation.
                (Some(_), Some(err)) => vec![Err(Error::multiple(err.span()))],

                // There is a single annotation, as it should.
                // Parse the annotation and emmit the source code for this field
                (Some(attr), None) => {
                    let tags = attr
                        .parse_meta() // -> Meta
                        .map_err(|_| Error::new(ErrorKind::ParseError, attr.span()))
                        .and_then(parser::parse_meta); // -> Result<Vec<Tag>>

                    match tags {
                        Err(error) => vec![Err(error)],
                        Ok(tags) => tags
                            .into_iter()
                            .map(|tag| {
                                parser::emmit_tag_tokens(
                                    &ident,
                                    &ty,
                                    &attr,
                                    &tag,
                                    &mut input_fields,
                                    &mut input_methods,
                                    &mut input_fields_set,
                                )
                            })
                            .collect(),
                    }
                }

                _ => unreachable!(),
            }
        })
        .collect::<Result<Vec<_>, Error>>()?;

    Ok((quote! { #( #field_body );*}, input_fields, input_methods))
}