Vendor iris, the in-house UI library, at iris/

Iris's decision: it lives in this repository for now, included by path,
with its history left in the iris/iris repository on the gitea remote
(this is its main at 7b54aaf, byte-identical to the public GitHub copy).
It gets its own repository back once it has proved itself here.

RUST.md's I0 records the decision and what the first build said: the
tree does not compile on the current nightly because const_trait_impl
now requires traits to be declared 'const trait', which is the first
item of I0b.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

iris/macro/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "iris-macro"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+proc-macro2 = "1.0.103"
+quote = "1.0.42"
+syn = { version = "2.0.111", features = ["full"] }
+
+[lib]
+proc-macro = true

iris/macro/src/lib.rs

@@ -0,0 +1,196 @@
+extern crate proc_macro;
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{
+    Attribute, Block, Error, GenericParam, Generics, Ident, ItemStruct, ItemTrait, Signature,
+    Token, Type, Visibility,
+    parse::{Parse, ParseStream, Result},
+    parse_macro_input, parse_quote,
+    spanned::Spanned,
+};
+
+struct Input {
+    attrs: Vec<Attribute>,
+    vis: Visibility,
+    name: Ident,
+    generics: Generics,
+    fns: Vec<InputFn>,
+}
+
+struct InputFn {
+    sig: Signature,
+    body: Block,
+}
+
+impl Parse for Input {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let attrs = input.call(Attribute::parse_outer)?;
+        let vis = input.parse()?;
+        input.parse::<Token![trait]>()?;
+        let name = input.parse()?;
+        let generics = input.parse::<Generics>()?;
+        input.parse::<Token![;]>()?;
+        let mut fns = Vec::new();
+        while !input.is_empty() {
+            let sig = input.parse()?;
+            let body = input.parse()?;
+            fns.push(InputFn { sig, body })
+        }
+        if !input.is_empty() {
+            input.error("function expected");
+        }
+        Ok(Input {
+            attrs,
+            vis,
+            name,
+            generics,
+            fns,
+        })
+    }
+}
+
+#[proc_macro]
+pub fn widget_trait(input: TokenStream) -> TokenStream {
+    let Input {
+        attrs,
+        vis,
+        name,
+        mut generics,
+        fns,
+    } = parse_macro_input!(input as Input);
+
+    let sigs: Vec<_> = fns.iter().map(|f| f.sig.clone()).collect();
+    let impls: Vec<_> = fns
+        .iter()
+        .map(|InputFn { sig, body }| quote! { #sig #body })
+        .collect();
+
+    let Some(GenericParam::Type(state)) = generics.params.first() else {
+        return Error::new(name.span(), "expected state generic parameter")
+            .into_compile_error()
+            .into();
+    };
+
+    let state = &state.ident;
+
+    generics
+        .params
+        .push(parse_quote!(WL: WidgetLike<#state, Tag>));
+    generics.params.push(parse_quote!(Tag));
+
+    let mut trai: ItemTrait = parse_quote!(
+        #vis trait #name #generics {
+            #(#sigs;)*
+        }
+    );
+
+    trai.attrs = attrs;
+
+    quote! {
+        #trai
+
+        impl #generics #name<Rsc, WL, Tag> for WL {
+            #(#impls)*
+        }
+    }
+    .into()
+}
+
+#[proc_macro_derive(DefaultUiState, attributes(default_ui_state))]
+pub fn derive_default_ui_state(input: TokenStream) -> TokenStream {
+    let mut output = proc_macro2::TokenStream::new();
+
+    let state: ItemStruct = parse_macro_input!(input);
+
+    let mut found_attr = false;
+    let mut state_field = None;
+    for field in &state.fields {
+        if !found_attr
+            && let Type::Path(path) = &field.ty
+            && path.path.is_ident("DefaultUiState")
+        {
+            state_field = Some(field);
+        }
+        let Some(attr) = field
+            .attrs
+            .iter()
+            .find(|a| a.path().is_ident("default_ui_state"))
+        else {
+            continue;
+        };
+        if found_attr {
+            output.extend(
+                Error::new(
+                    attr.span(),
+                    "cannot have more than one default_ui_state attribute",
+                )
+                .into_compile_error(),
+            );
+            continue;
+        }
+        found_attr = true;
+        state_field = Some(field);
+    }
+    let Some(field) = state_field else {
+        output.extend(
+            Error::new(state.ident.span(), "no DefaultUiState field found").into_compile_error(),
+        );
+        return output.into();
+    };
+    let sname = &state.ident;
+    let fname = field.ident.as_ref().unwrap();
+    output.extend(quote! {
+        impl iris::default::HasDefaultUiState for #sname {
+            fn default_state(&self) -> &iris::default::DefaultUiState {
+                &self.#fname
+            }
+            fn default_state_mut(&mut self) -> &mut iris::default::DefaultUiState {
+                &mut self.#fname
+            }
+        }
+    });
+    output.into()
+}
+
+#[proc_macro_derive(WidgetView, attributes(root))]
+pub fn derive_widget_view(input: TokenStream) -> TokenStream {
+    let mut output = proc_macro2::TokenStream::new();
+
+    let state: ItemStruct = parse_macro_input!(input);
+
+    let mut found_attr = false;
+    let mut state_field = None;
+    for field in &state.fields {
+        let Some(attr) = field.attrs.iter().find(|a| a.path().is_ident("root")) else {
+            continue;
+        };
+        if found_attr {
+            output.extend(
+                Error::new(attr.span(), "cannot have more than one root widget")
+                    .into_compile_error(),
+            );
+            continue;
+        }
+        found_attr = true;
+        state_field = Some(field);
+    }
+    let Some(field) = state_field else {
+        output.extend(
+            Error::new(state.ident.span(), "no root widget field found (#[root])")
+                .into_compile_error(),
+        );
+        return output.into();
+    };
+    let sname = &state.ident;
+    let fname = field.ident.as_ref().unwrap();
+    let fty = &field.ty;
+    output.extend(quote! {
+        impl iris::core::WidgetView for #sname {
+            type Widget = <#fty as iris::core::HasWidget>::Widget;
+            fn root(&self) -> #fty {
+                self.#fname
+            }
+        }
+    });
+    output.into()
+}