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style: Add a special, explicit path for lazy style resolution and use it for GetComputedStyle.

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MozReview-Commit-ID: KAM9mVoxCHE
This commit is contained in:
Bobby Holley 2016-12-28 11:21:40 +08:00 • committed by Cameron McCormack
parent 7e3c9e2197
commit ab71b29959
7 changed files with 176 additions and 119 deletions
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59
components/layout/query.rs
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@ -6,7 +6,7 @@
use app_units::Au;
use construct::ConstructionResult;
use context::{ScopedThreadLocalLayoutContext, SharedLayoutContext};
use context::SharedLayoutContext;
use euclid::point::Point2D;
use euclid::rect::Rect;
use euclid::size::Size2D;
@ -29,7 +29,7 @@ use std::cmp::{min, max};
use std::ops::Deref;
use std::sync::{Arc, Mutex};
use style::computed_values;
use style::context::StyleContext;
use style::context::{StyleContext, ThreadLocalStyleContext};
use style::dom::TElement;
use style::logical_geometry::{WritingMode, BlockFlowDirection, InlineBaseDirection};
use style::properties::{style_structs, PropertyId, PropertyDeclarationId, LonghandId};
@ -626,37 +626,46 @@ pub fn process_node_scroll_area_request< N: LayoutNode>(requested_node: N, layou
/// Return the resolved value of property for a given (pseudo)element.
/// https://drafts.csswg.org/cssom/#resolved-value
pub fn process_resolved_style_request<'a, N>(shared: &SharedLayoutContext,
requested_node: N,
node: N,
pseudo: &Option<PseudoElement>,
property: &PropertyId,
layout_root: &mut Flow) -> String
where N: LayoutNode,
{
use style::traversal::{clear_descendant_data, style_element_in_display_none_subtree};
let element = requested_node.as_element().unwrap();
use style::traversal::resolve_style;
let element = node.as_element().unwrap();
// We call process_resolved_style_request after performing a whole-document
// traversal, so the only reason we wouldn't have an up-to-date style here
// is that the requested node is in a display:none subtree. We currently
// maintain the invariant that elements in display:none subtrees always have
// no ElementData, so we need to temporarily bend those invariants here, and
// then throw them the style data away again before returning to preserve them.
// We could optimize this later to keep the style data cached somehow, but
// we'd need a mechanism to prevent detect when it's stale (since we don't
// traverse display:none subtrees during restyle).
let display_none_root = if element.get_data().is_none() {
let mut tlc = ScopedThreadLocalLayoutContext::new(shared);
let context = StyleContext {
shared: &shared.style_context,
thread_local: &mut tlc.style_context,
};
// traversal, so in the common case, the element is styled.
if element.get_data().is_some() {
return process_resolved_style_request_internal(node, pseudo, property, layout_root);
}
Some(style_element_in_display_none_subtree(&context, element,
&|e| e.as_node().initialize_data()))
} else {
None
// However, the element may be in a display:none subtree. The style system
// has a mechanism to give us that within a defined scope (after which point
// it's cleared to maintained style system invariants).
let mut tlc = ThreadLocalStyleContext::new(&shared.style_context);
let context = StyleContext {
shared: &shared.style_context,
thread_local: &mut tlc,
};
let mut result = None;
let ensure = |el: N::ConcreteElement| el.as_node().initialize_data();
let clear = |el: N::ConcreteElement| el.as_node().clear_data();
resolve_style(&context, element, &ensure, &clear, |_: &_| {
let s = process_resolved_style_request_internal(node, pseudo, property, layout_root);
result = Some(s);
});
result.unwrap()
}
/// The primary resolution logic, which assumes that the element is styled.
fn process_resolved_style_request_internal<'a, N>(requested_node: N,
pseudo: &Option<PseudoElement>,
property: &PropertyId,
layout_root: &mut Flow) -> String
where N: LayoutNode,
{
let layout_el = requested_node.to_threadsafe().as_element().unwrap();
let layout_el = match *pseudo {
Some(PseudoElement::Before) => layout_el.get_before_pseudo(),
@ -691,10 +700,6 @@ pub fn process_resolved_style_request<'a, N>(shared: &SharedLayoutContext,
}
};
// Clear any temporarily-resolved data to maintain our invariants. See the comment
// at the top of this function.
display_none_root.map(|r| clear_descendant_data(r, &|e| e.as_node().clear_data()));
let positioned = match style.get_box().position {
position::computed_value::T::relative |
/*position::computed_value::T::sticky |*/