зеркало из https://github.com/mozilla/gecko-dev.git
96 строки
2.9 KiB
Rust
96 строки
2.9 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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//! A structure to collect information about the cascade.
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#![deny(missing_docs)]
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use dom::TNode;
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use properties::{DeclaredValue, PropertyDeclaration};
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use style_traits::HasViewportPercentage;
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/// A structure to collect information about the cascade.
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///
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/// This is useful to gather information about what an element is affected by,
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/// and can be used in the future to track optimisations like when a
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/// non-inherited property is explicitly inherited, in order to cut-off the
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/// traversal.
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pub struct CascadeInfo {
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/// Whether we've seen viewport units so far.
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pub saw_viewport_units: bool,
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/// Whether the cascade has been marked as finished. This is a debug-only
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/// flag to ensure `finish` is called, given it's optional to not pass a
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/// `CascadeInfo`.
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#[cfg(debug_assertions)]
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finished: bool,
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}
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impl CascadeInfo {
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/// Construct a new `CascadeInfo`.
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#[cfg(debug_assertions)]
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pub fn new() -> Self {
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CascadeInfo {
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saw_viewport_units: false,
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finished: false,
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}
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}
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/// Construct a new `CascadeInfo`.
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#[cfg(not(debug_assertions))]
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pub fn new() -> Self {
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CascadeInfo {
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saw_viewport_units: false,
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}
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}
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/// Called when a property is cascaded.
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///
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/// NOTE: We can add a vast amount of information here.
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#[inline]
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pub fn on_cascade_property<T>(&mut self,
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_property_declaration: &PropertyDeclaration,
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value: &DeclaredValue<T>)
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where T: HasViewportPercentage,
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{
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// TODO: we can be smarter and keep a property bitfield to keep track of
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// the last applying rule.
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if value.has_viewport_percentage() {
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self.saw_viewport_units = true;
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}
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}
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#[cfg(debug_assertions)]
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fn mark_as_finished_if_appropriate(&mut self) {
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self.finished = true;
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}
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#[cfg(not(debug_assertions))]
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fn mark_as_finished_if_appropriate(&mut self) {}
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/// Called when the cascade is finished, in order to use the information
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/// we've collected.
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///
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/// Currently used for styling to mark a node as needing restyling when the
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/// viewport size changes.
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#[allow(unsafe_code)]
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pub fn finish<N: TNode>(mut self, node: &N) {
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self.mark_as_finished_if_appropriate();
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if self.saw_viewport_units {
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unsafe {
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node.set_dirty_on_viewport_size_changed();
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}
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}
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}
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}
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#[cfg(debug_assertions)]
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impl Drop for CascadeInfo {
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fn drop(&mut self) {
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debug_assert!(self.finished,
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"Didn't use the result of CascadeInfo, if you don't need \
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it, consider passing None");
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}
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}
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