diff options
Diffstat (limited to 'components/style_derive/to_css.rs')
| -rw-r--r-- | components/style_derive/to_css.rs | 46 |
1 files changed, 43 insertions, 3 deletions
diff --git a/components/style_derive/to_css.rs b/components/style_derive/to_css.rs index 774add083fa..f85fe1ce418 100644 --- a/components/style_derive/to_css.rs +++ b/components/style_derive/to_css.rs @@ -15,9 +15,12 @@ pub fn derive(input: syn::DeriveInput) -> quote::Tokens { } let style = synstructure::BindStyle::Ref.into(); - let match_body = synstructure::each_variant(&input, &style, |bindings, _| { + let match_body = synstructure::each_variant(&input, &style, |bindings, variant| { if bindings.is_empty() { - panic!("unit variants are not yet supported"); + let identifier = to_css_identifier(variant.ident.as_ref()); + return Some(quote! { + ::std::fmt::Write::write_str(dest, #identifier) + }); } let (first, rest) = bindings.split_first().expect("unit variants are not yet supported"); where_clause.predicates.push(where_predicate(first.field.ty.clone())); @@ -28,7 +31,7 @@ pub fn derive(input: syn::DeriveInput) -> quote::Tokens { where_clause.predicates.push(where_predicate(binding.field.ty.clone())); expr = quote! { #expr?; - dest.write_str(" ")?; + ::std::fmt::Write::write_str(dest, " ")?; ::style_traits::ToCss::to_css(#binding, dest) }; } @@ -68,3 +71,40 @@ fn where_predicate(ty: syn::Ty) -> syn::WherePredicate { )], }) } + +/// Transforms "FooBar" to "foo-bar". +/// +/// If the first Camel segment is "Moz"" or "Webkit", the result string +/// is prepended with "-". +fn to_css_identifier(mut camel_case: &str) -> String { + let mut first = true; + let mut result = String::with_capacity(camel_case.len()); + while let Some(segment) = split_camel_segment(&mut camel_case) { + if first { + match segment { + "Moz" | "Webkit" => first = false, + _ => {}, + } + } + if !first { + result.push_str("-"); + } + first = false; + result.push_str(&segment.to_lowercase()); + } + result +} + +/// Given "FooBar", returns "Foo" and sets `camel_case` to "Bar". +fn split_camel_segment<'input>(camel_case: &mut &'input str) -> Option<&'input str> { + let index = match camel_case.chars().next() { + None => return None, + Some(ch) => ch.len_utf8(), + }; + let end_position = camel_case[index..] + .find(char::is_uppercase) + .map_or(camel_case.len(), |pos| index + pos); + let result = &camel_case[..end_position]; + *camel_case = &camel_case[end_position..]; + Some(result) +} |