Checkpoint

crates/gpui2_macros/src/derive_element.rs

@@ -0,0 +1,92 @@
+use proc_macro::TokenStream;
+use proc_macro2::Ident;
+use quote::quote;
+use syn::{parse_macro_input, parse_quote, DeriveInput, GenericParam, Generics};
+
+use crate::derive_into_element::impl_into_element;
+
+pub fn derive_element(input: TokenStream) -> TokenStream {
+    let ast = parse_macro_input!(input as DeriveInput);
+    let type_name = ast.ident;
+    let placeholder_view_generics: Generics = parse_quote! { <V: 'static> };
+
+    let (impl_generics, type_generics, where_clause, view_type_name, lifetimes) =
+        if let Some(first_type_param) = ast.generics.params.iter().find_map(|param| {
+            if let GenericParam::Type(type_param) = param {
+                Some(type_param.ident.clone())
+            } else {
+                None
+            }
+        }) {
+            let mut lifetimes = vec![];
+            for param in ast.generics.params.iter() {
+                if let GenericParam::Lifetime(lifetime_def) = param {
+                    lifetimes.push(lifetime_def.lifetime.clone());
+                }
+            }
+            let generics = ast.generics.split_for_impl();
+            (
+                generics.0,
+                Some(generics.1),
+                generics.2,
+                first_type_param,
+                lifetimes,
+            )
+        } else {
+            let generics = placeholder_view_generics.split_for_impl();
+            let placeholder_view_type_name: Ident = parse_quote! { V };
+            (
+                generics.0,
+                None,
+                generics.2,
+                placeholder_view_type_name,
+                vec![],
+            )
+        };
+
+    let lifetimes = if !lifetimes.is_empty() {
+        quote! { <#(#lifetimes),*> }
+    } else {
+        quote! {}
+    };
+
+    let impl_into_element = impl_into_element(
+        &impl_generics,
+        &view_type_name,
+        &type_name,
+        &type_generics,
+        &where_clause,
+    );
+
+    let gen = quote! {
+        impl #impl_generics playground::element::Element<#view_type_name> for #type_name #type_generics
+        #where_clause
+        {
+            type PaintState = playground::element::AnyElement<#view_type_name #lifetimes>;
+
+            fn layout(
+                &mut self,
+                view: &mut V,
+                cx: &mut playground::element::LayoutContext<V>,
+            ) -> anyhow::Result<(playground::element::LayoutId, Self::PaintState)> {
+                let mut rendered_element = self.render(view, cx).into_element().into_any();
+                let layout_id = rendered_element.layout(view, cx)?;
+                Ok((layout_id, rendered_element))
+            }
+
+            fn paint(
+                &mut self,
+                view: &mut V,
+                layout: &playground::element::Layout,
+                rendered_element: &mut Self::PaintState,
+                cx: &mut playground::element::PaintContext<V>,
+            ) {
+                rendered_element.paint(view, layout.bounds.origin(), cx);
+            }
+        }
+
+        #impl_into_element
+    };
+
+    gen.into()
+}