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-rw-r--r--servo/components/style_derive/to_css.rs396
1 files changed, 396 insertions, 0 deletions
diff --git a/servo/components/style_derive/to_css.rs b/servo/components/style_derive/to_css.rs
new file mode 100644
index 0000000000..aa33536648
--- /dev/null
+++ b/servo/components/style_derive/to_css.rs
@@ -0,0 +1,396 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use darling::util::Override;
+use derive_common::cg;
+use proc_macro2::{Span, TokenStream};
+use quote::{ToTokens, TokenStreamExt};
+use syn::{self, Data, Ident, Path, WhereClause};
+use synstructure::{BindingInfo, Structure, VariantInfo};
+
+fn derive_bitflags(input: &syn::DeriveInput, bitflags: &CssBitflagAttrs) -> TokenStream {
+ let name = &input.ident;
+ let mut body = TokenStream::new();
+ for (rust_name, css_name) in bitflags.single_flags() {
+ let rust_ident = Ident::new(&rust_name, Span::call_site());
+ body.append_all(quote! {
+ if *self == Self::#rust_ident {
+ return dest.write_str(#css_name);
+ }
+ });
+ }
+
+ body.append_all(quote! {
+ let mut has_any = false;
+ });
+
+ if bitflags.overlapping_bits {
+ body.append_all(quote! {
+ let mut serialized = Self::empty();
+ });
+ }
+
+ for (rust_name, css_name) in bitflags.mixed_flags() {
+ let rust_ident = Ident::new(&rust_name, Span::call_site());
+ let serialize = quote! {
+ if has_any {
+ dest.write_char(' ')?;
+ }
+ has_any = true;
+ dest.write_str(#css_name)?;
+ };
+ if bitflags.overlapping_bits {
+ body.append_all(quote! {
+ if self.contains(Self::#rust_ident) && !serialized.intersects(Self::#rust_ident) {
+ #serialize
+ serialized.insert(Self::#rust_ident);
+ }
+ });
+ } else {
+ body.append_all(quote! {
+ if self.intersects(Self::#rust_ident) {
+ #serialize
+ }
+ });
+ }
+ }
+
+ body.append_all(quote! {
+ Ok(())
+ });
+
+ quote! {
+ impl style_traits::ToCss for #name {
+ #[allow(unused_variables)]
+ #[inline]
+ fn to_css<W>(
+ &self,
+ dest: &mut style_traits::CssWriter<W>,
+ ) -> std::fmt::Result
+ where
+ W: std::fmt::Write,
+ {
+ #body
+ }
+ }
+ }
+}
+
+pub fn derive(mut input: syn::DeriveInput) -> TokenStream {
+ let mut where_clause = input.generics.where_clause.take();
+ for param in input.generics.type_params() {
+ cg::add_predicate(&mut where_clause, parse_quote!(#param: style_traits::ToCss));
+ }
+
+ let input_attrs = cg::parse_input_attrs::<CssInputAttrs>(&input);
+ if matches!(input.data, Data::Enum(..)) || input_attrs.bitflags.is_some() {
+ assert!(
+ input_attrs.function.is_none(),
+ "#[css(function)] is not allowed on enums or bitflags"
+ );
+ assert!(
+ !input_attrs.comma,
+ "#[css(comma)] is not allowed on enums or bitflags"
+ );
+ }
+
+ if let Some(ref bitflags) = input_attrs.bitflags {
+ assert!(
+ !input_attrs.derive_debug,
+ "Bitflags can derive debug on their own"
+ );
+ assert!(where_clause.is_none(), "Generic bitflags?");
+ return derive_bitflags(&input, bitflags);
+ }
+
+ let match_body = {
+ let s = Structure::new(&input);
+ s.each_variant(|variant| derive_variant_arm(variant, &mut where_clause))
+ };
+ input.generics.where_clause = where_clause;
+
+ let name = &input.ident;
+ let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+
+ let mut impls = quote! {
+ impl #impl_generics style_traits::ToCss for #name #ty_generics #where_clause {
+ #[allow(unused_variables)]
+ #[inline]
+ fn to_css<W>(
+ &self,
+ dest: &mut style_traits::CssWriter<W>,
+ ) -> std::fmt::Result
+ where
+ W: std::fmt::Write,
+ {
+ match *self {
+ #match_body
+ }
+ }
+ }
+ };
+
+ if input_attrs.derive_debug {
+ impls.append_all(quote! {
+ impl #impl_generics std::fmt::Debug for #name #ty_generics #where_clause {
+ fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+ style_traits::ToCss::to_css(
+ self,
+ &mut style_traits::CssWriter::new(f),
+ )
+ }
+ }
+ });
+ }
+
+ impls
+}
+
+fn derive_variant_arm(variant: &VariantInfo, generics: &mut Option<WhereClause>) -> TokenStream {
+ let bindings = variant.bindings();
+ let identifier = cg::to_css_identifier(&variant.ast().ident.to_string());
+ let ast = variant.ast();
+ let variant_attrs = cg::parse_variant_attrs_from_ast::<CssVariantAttrs>(&ast);
+ let separator = if variant_attrs.comma { ", " } else { " " };
+
+ if variant_attrs.skip {
+ return quote!(Ok(()));
+ }
+ if variant_attrs.dimension {
+ assert_eq!(bindings.len(), 1);
+ assert!(
+ variant_attrs.function.is_none() && variant_attrs.keyword.is_none(),
+ "That makes no sense"
+ );
+ }
+
+ let mut expr = if let Some(keyword) = variant_attrs.keyword {
+ assert!(bindings.is_empty());
+ quote! {
+ std::fmt::Write::write_str(dest, #keyword)
+ }
+ } else if !bindings.is_empty() {
+ derive_variant_fields_expr(bindings, generics, separator)
+ } else {
+ quote! {
+ std::fmt::Write::write_str(dest, #identifier)
+ }
+ };
+
+ if variant_attrs.dimension {
+ expr = quote! {
+ #expr?;
+ std::fmt::Write::write_str(dest, #identifier)
+ }
+ } else if let Some(function) = variant_attrs.function {
+ let mut identifier = function.explicit().map_or(identifier, |name| name);
+ identifier.push('(');
+ expr = quote! {
+ std::fmt::Write::write_str(dest, #identifier)?;
+ #expr?;
+ std::fmt::Write::write_str(dest, ")")
+ }
+ }
+ expr
+}
+
+fn derive_variant_fields_expr(
+ bindings: &[BindingInfo],
+ where_clause: &mut Option<WhereClause>,
+ separator: &str,
+) -> TokenStream {
+ let mut iter = bindings
+ .iter()
+ .filter_map(|binding| {
+ let attrs = cg::parse_field_attrs::<CssFieldAttrs>(&binding.ast());
+ if attrs.skip {
+ return None;
+ }
+ Some((binding, attrs))
+ })
+ .peekable();
+
+ let (first, attrs) = match iter.next() {
+ Some(pair) => pair,
+ None => return quote! { Ok(()) },
+ };
+ if attrs.field_bound {
+ let ty = &first.ast().ty;
+ // TODO(emilio): IntoIterator might not be enough for every type of
+ // iterable thing (like ArcSlice<> or what not). We might want to expose
+ // an `item = "T"` attribute to handle that in the future.
+ let predicate = if attrs.iterable {
+ parse_quote!(<#ty as IntoIterator>::Item: style_traits::ToCss)
+ } else {
+ parse_quote!(#ty: style_traits::ToCss)
+ };
+ cg::add_predicate(where_clause, predicate);
+ }
+ if !attrs.iterable && iter.peek().is_none() {
+ let mut expr = quote! { style_traits::ToCss::to_css(#first, dest) };
+ if let Some(condition) = attrs.skip_if {
+ expr = quote! {
+ if !#condition(#first) {
+ #expr
+ }
+ }
+ }
+
+ if let Some(condition) = attrs.contextual_skip_if {
+ expr = quote! {
+ if !#condition(#(#bindings), *) {
+ #expr
+ }
+ }
+ }
+ return expr;
+ }
+
+ let mut expr = derive_single_field_expr(first, attrs, where_clause, bindings);
+ for (binding, attrs) in iter {
+ derive_single_field_expr(binding, attrs, where_clause, bindings).to_tokens(&mut expr)
+ }
+
+ quote! {{
+ let mut writer = style_traits::values::SequenceWriter::new(dest, #separator);
+ #expr
+ Ok(())
+ }}
+}
+
+fn derive_single_field_expr(
+ field: &BindingInfo,
+ attrs: CssFieldAttrs,
+ where_clause: &mut Option<WhereClause>,
+ bindings: &[BindingInfo],
+) -> TokenStream {
+ let mut expr = if attrs.iterable {
+ if let Some(if_empty) = attrs.if_empty {
+ return quote! {
+ {
+ let mut iter = #field.iter().peekable();
+ if iter.peek().is_none() {
+ writer.raw_item(#if_empty)?;
+ } else {
+ for item in iter {
+ writer.item(&item)?;
+ }
+ }
+ }
+ };
+ }
+ quote! {
+ for item in #field.iter() {
+ writer.item(&item)?;
+ }
+ }
+ } else if attrs.represents_keyword {
+ let ident = field
+ .ast()
+ .ident
+ .as_ref()
+ .expect("Unnamed field with represents_keyword?");
+ let ident = cg::to_css_identifier(&ident.to_string()).replace("_", "-");
+ quote! {
+ if *#field {
+ writer.raw_item(#ident)?;
+ }
+ }
+ } else {
+ if attrs.field_bound {
+ let ty = &field.ast().ty;
+ cg::add_predicate(where_clause, parse_quote!(#ty: style_traits::ToCss));
+ }
+ quote! { writer.item(#field)?; }
+ };
+
+ if let Some(condition) = attrs.skip_if {
+ expr = quote! {
+ if !#condition(#field) {
+ #expr
+ }
+ }
+ }
+
+ if let Some(condition) = attrs.contextual_skip_if {
+ expr = quote! {
+ if !#condition(#(#bindings), *) {
+ #expr
+ }
+ }
+ }
+
+ expr
+}
+
+#[derive(Default, FromMeta)]
+#[darling(default)]
+pub struct CssBitflagAttrs {
+ /// Flags that can only go on their own, comma-separated.
+ pub single: Option<String>,
+ /// Flags that can go mixed with each other, comma-separated.
+ pub mixed: Option<String>,
+ /// Extra validation of the resulting mixed flags.
+ pub validate_mixed: Option<Path>,
+ /// Whether there are overlapping bits we need to take care of when
+ /// serializing.
+ pub overlapping_bits: bool,
+}
+
+impl CssBitflagAttrs {
+ /// Returns a vector of (rust_name, css_name) of a given flag list.
+ fn names(s: &Option<String>) -> Vec<(String, String)> {
+ let s = match s {
+ Some(s) => s,
+ None => return vec![],
+ };
+ s.split(',')
+ .map(|css_name| (cg::to_scream_case(css_name), css_name.to_owned()))
+ .collect()
+ }
+
+ pub fn single_flags(&self) -> Vec<(String, String)> {
+ Self::names(&self.single)
+ }
+
+ pub fn mixed_flags(&self) -> Vec<(String, String)> {
+ Self::names(&self.mixed)
+ }
+}
+
+#[derive(Default, FromDeriveInput)]
+#[darling(attributes(css), default)]
+pub struct CssInputAttrs {
+ pub derive_debug: bool,
+ // Here because structs variants are also their whole type definition.
+ pub function: Option<Override<String>>,
+ // Here because structs variants are also their whole type definition.
+ pub comma: bool,
+ pub bitflags: Option<CssBitflagAttrs>,
+}
+
+#[derive(Default, FromVariant)]
+#[darling(attributes(css), default)]
+pub struct CssVariantAttrs {
+ pub function: Option<Override<String>>,
+ // Here because structs variants are also their whole type definition.
+ pub derive_debug: bool,
+ pub comma: bool,
+ pub bitflags: Option<CssBitflagAttrs>,
+ pub dimension: bool,
+ pub keyword: Option<String>,
+ pub skip: bool,
+}
+
+#[derive(Default, FromField)]
+#[darling(attributes(css), default)]
+pub struct CssFieldAttrs {
+ pub if_empty: Option<String>,
+ pub field_bound: bool,
+ pub iterable: bool,
+ pub skip: bool,
+ pub represents_keyword: bool,
+ pub contextual_skip_if: Option<Path>,
+ pub skip_if: Option<Path>,
+}