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style: Add some attributes for SpecifiedValueInfo to help deriving more from types.

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Bug: 1434130
Reviewed-by: emilio
MozReview-Commit-ID: IyohSTbUO31
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Xidorn Quan 2018-04-29 09:03:31 +10:00 • committed by Emilio Cobos Álvarez
parent 0021c70c08
commit 0f7f9eebc0
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17 changed files with 137 additions and 36 deletions
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30
components/style_traits/specified_value_info.rs
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@ -27,6 +27,36 @@ pub mod CssType {
pub type KeywordsCollectFn<'a> = &'a mut FnMut(&[&'static str]);
/// Information of values of a given specified value type.
///
/// This trait is derivable with `#[derive(SpecifiedValueInfo)]`.
///
/// The algorithm traverses the type definition. For `SUPPORTED_TYPES`,
/// it puts an or'ed value of `SUPPORTED_TYPES` of all types it finds.
/// For `collect_completion_keywords`, it recursively invokes this
/// method on types found, and lists all keyword values and function
/// names following the same rule as `ToCss` in that method.
///
/// Some attributes of `ToCss` can affect the behavior, specifically:
/// * If `#[css(function)]` is found, the content inside the annotated
/// variant (or the whole type) isn't traversed, only the function
/// name is listed in `collect_completion_keywords`.
/// * If `#[css(skip)]` is found, the content inside the variant or
/// field is ignored.
/// * Values listed in `#[css(if_empty)]`, `#[css(aliases)]`, and
/// `#[css(keyword)]` are added into `collect_completion_keywords`.
///
/// In addition to `css` attributes, it also has `value_info` helper
/// attributes, including:
/// * `#[value_info(ty = "TYPE")]` can be used to specify a constant
/// from `CssType` to `SUPPORTED_TYPES`.
/// * `#[value_info(other_values = "value1,value2")]` can be used to
/// add other values related to a field, variant, or the type itself
/// into `collect_completion_keywords`.
/// * `#[value_info(starts_with_keyword)]` can be used on variants to
/// add the name of a non-unit variant (serialized like `ToCss`) into
/// `collect_completion_keywords`.
/// * `#[value_info(represents_keyword)]` can be used on fields into
/// `collect_completion_keywords`.
pub trait SpecifiedValueInfo {
/// Supported CssTypes by the given value type.
///