Struct style::invalidation::element::invalidation_map::Dependency

pub struct Dependency {
    pub selector: Selector<SelectorImpl>,
    pub selector_offset: usize,
}

Mapping between (partial) CompoundSelectors (and the combinator to their right) and the states and attributes they depend on.

In general, for all selectors in all applicable stylesheets of the form:

|a _ b _ c _ d _ e|

Where: * |b| and |d| are simple selectors that depend on state (like :hover) or attributes (like [attr...], .foo, or #foo). * |a|, |c|, and |e| are arbitrary simple selectors that do not depend on state or attributes.

We generate a Dependency for both |a _ b:X _| and |a _ b:X _ c _ d:Y _|, even though those selectors may not appear on their own in any stylesheet. This allows us to quickly scan through the dependency sites of all style rules and determine the maximum effect that a given state or attribute change may have on the style of elements in the document.

Fields

selector: Selector<SelectorImpl>

The dependency selector.

selector_offset: usize

The offset into the selector that we should match on.

Methods

impl Dependency

pub fn combinator(&self) -> Option<Combinator>

Returns the combinator to the right of the partial selector this dependency represents.

TODO(emilio): Consider storing inline if it helps cache locality?

pub fn affects_self(&self) -> bool

Whether this dependency affects the style of the element.

NOTE(emilio): pseudo-elements need to be here to account for eager pseudos, since they just grab the style from the originating element.

TODO(emilio): We could look at the selector itself to see if it's an eager pseudo, and return false here if not.

pub fn affects_descendants(&self) -> bool

Whether this dependency may affect style of any of our descendants.

pub fn affects_later_siblings(&self) -> bool

Whether this dependency may affect style of any of our later siblings.

Trait Implementations

impl Clone for Dependency

fn clone(&self) -> Dependency

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Dependency

fn fmt(&self, __arg_0: &mut Formatter) -> Result

Formats the value using the given formatter.

impl MallocSizeOf for Dependency

fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize

Measure the heap usage of all descendant heap-allocated structures, but not the space taken up by the value itself.

impl SelectorMapEntry for Dependency

Important traits for SelectorIter<'a, Impl>

impl<'a, Impl> Iterator for SelectorIter<'a, Impl> where
    Impl: SelectorImpl,  type Item = &'a Component<Impl>;

fn selector(&self) -> SelectorIter<SelectorImpl>

Gets the selector we should use to index in the selector map.