1use proc_macro::TokenStream;
 2use quote::quote;
 3use syn::{parse_macro_input, DeriveInput, GenericParam};
 4
 5pub fn derive_element(input: TokenStream) -> TokenStream {
 6    let ast = parse_macro_input!(input as DeriveInput);
 7    let type_name = ast.ident;
 8
 9    let mut state_type = quote! { () };
10
11    for param in &ast.generics.params {
12        if let GenericParam::Type(type_param) = param {
13            let type_ident = &type_param.ident;
14            state_type = quote! {#type_ident};
15        }
16    }
17
18    let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
19
20    let gen = quote! {
21        impl #impl_generics gpui3::Element for #type_name #ty_generics
22        #where_clause
23        {
24            type State = #state_type;
25            type FrameState = gpui3::AnyElement<#state_type>;
26
27            fn layout(
28                &mut self,
29                state: &mut #state_type,
30                cx: &mut gpui3::ViewContext<V>,
31            ) -> anyhow::Result<(gpui3::LayoutId, Self::FrameState)> {
32                let mut rendered_element = self.render(state, cx).into_element().into_any();
33                let layout_id = rendered_element.layout(state, cx)?;
34                Ok((layout_id, rendered_element))
35            }
36
37            fn paint(
38                &mut self,
39                layout: &gpui3::Layout,
40                state: &mut #state_type,
41                rendered_element: &mut Self::FrameState,
42                cx: &mut gpui3::ViewContext<V>,
43            ) {
44                rendered_element.paint(layout.origin, state, cx);
45            }
46        }
47    };
48
49    gen.into()
50}