New context system (#3497)

4 files changed, 38 insertions, 3 deletions

diff --git a/crates/typst-macros/src/elem.rs b/crates/typst-macros/src/elem.rs
index 81548dd7..f14d3350 100644
--- a/crates/typst-macros/src/elem.rs
+++ b/crates/typst-macros/src/elem.rs
@@ -617,6 +617,7 @@ fn create_native_elem_impl(element: &Elem) -> TokenStream {
             vtable:  <#ident as #foundations::Capable>::vtable,
             field_id: |name| name.parse().ok().map(|id: Fields| id as u8),
             field_name: |id| id.try_into().ok().map(Fields::to_str),
+            field_from_styles: <#ident as #foundations::Fields>::field_from_styles,
             local_name: #local_name,
             scope: #foundations::Lazy::new(|| #scope),
             params: #foundations::Lazy::new(|| ::std::vec![#(#params),*])
@@ -866,6 +867,20 @@ fn create_fields_impl(element: &Elem) -> TokenStream {
         quote! { Fields::#enum_ident => #expr }
     });
 
+    // Fields that can be accessed using the `field_from_styles` method.
+    let field_from_styles_arms = element.visible_fields().map(|field| {
+        let Field { enum_ident, .. } = field;
+
+        let expr = if field.required || field.synthesized {
+            quote! { None }
+        } else {
+            let value = create_style_chain_access(field, false, quote!(None));
+            quote! { Some(#into_value(#value)) }
+        };
+
+        quote! { Fields::#enum_ident => #expr }
+    });
+
     // Sets fields from the style chain.
     let materializes = visible_non_ghost()
         .filter(|field| !field.required && !field.synthesized)
@@ -939,6 +954,14 @@ fn create_fields_impl(element: &Elem) -> TokenStream {
                 }
             }
 
+            fn field_from_styles(id: u8, styles: #foundations::StyleChain) -> Option<#foundations::Value> {
+                let id = Fields::try_from(id).ok()?;
+                match id {
+                    #(#field_from_styles_arms,)*
+                    _ => None,
+                }
+            }
+
             fn materialize(&mut self, styles: #foundations::StyleChain) {
                #(#materializes)*
             }
diff --git a/crates/typst-macros/src/func.rs b/crates/typst-macros/src/func.rs
index 953df428..728ab05b 100644
--- a/crates/typst-macros/src/func.rs
+++ b/crates/typst-macros/src/func.rs
@@ -24,6 +24,7 @@ struct Func {
     constructor: bool,
     keywords: Vec<String>,
     parent: Option<syn::Type>,
+    contextual: bool,
     docs: String,
     vis: syn::Visibility,
     ident: Ident,
@@ -37,6 +38,7 @@ struct Func {
 struct SpecialParams {
     self_: Option<Param>,
     engine: bool,
+    context: bool,
     args: bool,
     span: bool,
 }
@@ -67,6 +69,7 @@ enum Binding {
 /// The `..` in `#[func(..)]`.
 pub struct Meta {
     pub scope: bool,
+    pub contextual: bool,
     pub name: Option<String>,
     pub title: Option<String>,
     pub constructor: bool,
@@ -78,6 +81,7 @@ impl Parse for Meta {
     fn parse(input: ParseStream) -> Result<Self> {
         Ok(Self {
             scope: parse_flag::<kw::scope>(input)?,
+            contextual: parse_flag::<kw::contextual>(input)?,
             name: parse_string::<kw::name>(input)?,
             title: parse_string::<kw::title>(input)?,
             constructor: parse_flag::<kw::constructor>(input)?,
@@ -117,6 +121,7 @@ fn parse(stream: TokenStream, item: &syn::ItemFn) -> Result<Func> {
         constructor: meta.constructor,
         keywords: meta.keywords,
         parent: meta.parent,
+        contextual: meta.contextual,
         docs,
         vis: item.vis.clone(),
         ident: item.sig.ident.clone(),
@@ -171,6 +176,7 @@ fn parse_param(
 
     match ident.to_string().as_str() {
         "engine" => special.engine = true,
+        "context" => special.context = true,
         "args" => special.args = true,
         "span" => special.span = true,
         _ => {
@@ -247,6 +253,7 @@ fn create_func_data(func: &Func) -> TokenStream {
         scope,
         parent,
         constructor,
+        contextual,
         ..
     } = func;
 
@@ -272,6 +279,7 @@ fn create_func_data(func: &Func) -> TokenStream {
             title: #title,
             docs: #docs,
             keywords: &[#(#keywords),*],
+            contextual: #contextual,
             scope: #foundations::Lazy::new(|| #scope),
             params: #foundations::Lazy::new(|| ::std::vec![#(#params),*]),
             returns:  #foundations::Lazy::new(|| <#returns as #foundations::Reflect>::output()),
@@ -320,12 +328,13 @@ fn create_wrapper_closure(func: &Func) -> TokenStream {
             .as_ref()
             .map(bind)
             .map(|tokens| quote! { #tokens, });
-        let vt_ = func.special.engine.then(|| quote! { engine, });
+        let engine_ = func.special.engine.then(|| quote! { engine, });
+        let context_ = func.special.context.then(|| quote! { context, });
         let args_ = func.special.args.then(|| quote! { args, });
         let span_ = func.special.span.then(|| quote! { args.span, });
         let forwarded = func.params.iter().filter(|param| !param.external).map(bind);
         quote! {
-            __typst_func(#self_ #vt_ #args_ #span_ #(#forwarded,)*)
+            __typst_func(#self_ #engine_ #context_ #args_ #span_ #(#forwarded,)*)
         }
     };
 
@@ -333,7 +342,7 @@ fn create_wrapper_closure(func: &Func) -> TokenStream {
     let ident = &func.ident;
     let parent = func.parent.as_ref().map(|ty| quote! { #ty:: });
     quote! {
-        |engine, args| {
+        |engine, context, args| {
             let __typst_func = #parent #ident;
             #handlers
             #finish
diff --git a/crates/typst-macros/src/lib.rs b/crates/typst-macros/src/lib.rs
index 5d340473..f92230ef 100644
--- a/crates/typst-macros/src/lib.rs
+++ b/crates/typst-macros/src/lib.rs
@@ -40,6 +40,8 @@ use syn::DeriveInput;
 /// You can customize some properties of the resulting function:
 /// - `scope`: Indicates that the function has an associated scope defined by
 ///   the `#[scope]` macro.
+/// - `contextual`: Indicates that the function makes use of context. This has
+///   no effect on the behaviour itself, but is used for the docs.
 /// - `name`: The functions's normal name (e.g. `min`). Defaults to the Rust
 ///   name in kebab-case.
 /// - `title`: The functions's title case name (e.g. `Minimum`). Defaults to the
diff --git a/crates/typst-macros/src/util.rs b/crates/typst-macros/src/util.rs
index 89880db1..bfe22285 100644
--- a/crates/typst-macros/src/util.rs
+++ b/crates/typst-macros/src/util.rs
@@ -255,6 +255,7 @@ pub mod kw {
     syn::custom_keyword!(span);
     syn::custom_keyword!(title);
     syn::custom_keyword!(scope);
+    syn::custom_keyword!(contextual);
     syn::custom_keyword!(cast);
     syn::custom_keyword!(constructor);
     syn::custom_keyword!(keywords);