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Auto merge of #17523 - emilio:cleanup-traversal, r=nox

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style: Cleanup traversal.rs

Mostly reflowing comments that have become too long or two short with
refactorings, and using consistent indentation.

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This commit is contained in:
bors-servo 2017-06-27 07:08:42 -07:00 • committed by GitHub
commit f93fccac57
1 changed files with 189 additions and 142 deletions
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331
components/style/traversal.rs
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@ -38,6 +38,7 @@ bitflags! {
/// Traverse without generating any change hints.
const FOR_RECONSTRUCT = 0x04,
/// Traverse triggered by CSS rule changes.
///
/// Traverse and update all elements with CSS animations since
/// @keyframes rules may have changed
const FOR_CSS_RULE_CHANGES = 0x08,
@ -67,8 +68,8 @@ impl TraversalFlags {
self.contains(FOR_CSS_RULE_CHANGES)
}
/// Returns true if the traversal is to compute the default computed
/// styles for an element.
/// Returns true if the traversal is to compute the default computed styles
/// for an element.
pub fn for_default_styles(&self) -> bool {
self.contains(FOR_DEFAULT_STYLES)
}
@ -102,7 +103,9 @@ pub enum LogBehavior {
}
use self::LogBehavior::*;
impl LogBehavior {
fn allow(&self) -> bool { matches!(*self, MayLog) }
fn allow(&self) -> bool {
matches!(*self, MayLog)
}
}
/// The kind of traversals we could perform.
@ -172,12 +175,13 @@ pub trait DomTraversal<E: TElement> : Sync {
/// The only communication between siblings is that they both
/// fetch-and-subtract the parent's children count. This makes it safe to
/// call durign the parallel traversal.
fn handle_postorder_traversal(&self,
thread_local: &mut Self::ThreadLocalContext,
root: OpaqueNode,
mut node: E::ConcreteNode,
children_to_process: isize)
{
fn handle_postorder_traversal(
&self,
thread_local: &mut Self::ThreadLocalContext,
root: OpaqueNode,
mut node: E::ConcreteNode,
children_to_process: isize
) {
// If the postorder step is a no-op, don't bother.
if !Self::needs_postorder_traversal() {
return;
@ -202,8 +206,8 @@ pub trait DomTraversal<E: TElement> : Sync {
node = parent.as_node();
}
} else {
// Otherwise record the number of children to process when the
// time comes.
// Otherwise record the number of children to process when the time
// comes.
node.as_element().unwrap()
.store_children_to_process(children_to_process);
}
@ -213,19 +217,22 @@ pub trait DomTraversal<E: TElement> : Sync {
/// a traversal is needed. Returns a token that allows the caller to prove
/// that the call happened.
///
/// The traversal_flag is used in Gecko.
/// The traversal_flags is used in Gecko.
///
/// If traversal_flag::UNSTYLED_CHILDREN_ONLY is specified, style newly-
/// appended children without restyling the parent.
///
/// If traversal_flag::ANIMATION_ONLY is specified, style only elements for
/// animations.
fn pre_traverse(root: E,
shared_context: &SharedStyleContext,
traversal_flags: TraversalFlags)
-> PreTraverseToken
{
fn pre_traverse(
root: E,
shared_context: &SharedStyleContext,
traversal_flags: TraversalFlags
) -> PreTraverseToken {
debug_assert!(!(traversal_flags.for_reconstruct() &&
traversal_flags.for_unstyled_children_only()),
"must not specify FOR_RECONSTRUCT in combination with UNSTYLED_CHILDREN_ONLY");
"must not specify FOR_RECONSTRUCT in combination with \
UNSTYLED_CHILDREN_ONLY");
if traversal_flags.for_unstyled_children_only() {
if root.borrow_data().map_or(true, |d| d.has_styles() && d.styles.is_display_none()) {
@ -253,16 +260,19 @@ pub trait DomTraversal<E: TElement> : Sync {
}
}
/// Returns true if traversal should visit a text node. The style system never
/// processes text nodes, but Servo overrides this to visit them for flow
/// construction when necessary.
/// Returns true if traversal should visit a text node. The style system
/// never processes text nodes, but Servo overrides this to visit them for
/// flow construction when necessary.
fn text_node_needs_traversal(node: E::ConcreteNode) -> bool {
debug_assert!(node.is_text_node());
false
}
/// Returns true if traversal is needed for the given node and subtree.
fn node_needs_traversal(node: E::ConcreteNode, traversal_flags: TraversalFlags) -> bool {
fn node_needs_traversal(
node: E::ConcreteNode,
traversal_flags: TraversalFlags
) -> bool {
// Non-incremental layout visits every node.
if is_servo_nonincremental_layout() {
return true;
@ -277,21 +287,19 @@ pub trait DomTraversal<E: TElement> : Sync {
Some(el) => el,
};
// If the element is native-anonymous and an ancestor frame will
// be reconstructed, the child and all its descendants will be
// destroyed. In that case, we wouldn't need to traverse the
// subtree...
// If the element is native-anonymous and an ancestor frame will be
// reconstructed, the child and all its descendants will be destroyed.
// In that case, we wouldn't need to traverse the subtree...
//
// Except if there could be transitions of pseudo-elements, in
// which
// Except if there could be transitions of pseudo-elements, in which
// case we still need to process them, unfortunately.
//
// We need to conservatively continue the traversal to style the
// pseudo-element in order to properly process potentially-new
// transitions that we won't see otherwise.
//
// But it may be that we no longer match, so detect that case
// and act appropriately here.
// But it may be that we no longer match, so detect that case and act
// appropriately here.
if el.is_native_anonymous() {
if let Some(parent) = el.traversal_parent() {
let parent_data = parent.borrow_data().unwrap();
@ -322,9 +330,9 @@ pub trait DomTraversal<E: TElement> : Sync {
}
}
// In case of animation-only traversal we need to traverse
// the element if the element has animation only dirty
// descendants bit, animation-only restyle hint or recascade.
// In case of animation-only traversal we need to traverse the element
// if the element has animation only dirty descendants bit,
// animation-only restyle hint or recascade.
if traversal_flags.for_animation_only() {
// Skip elements that have no style data since animation-only
// restyle is not necessary for the elements.
@ -345,14 +353,14 @@ pub trait DomTraversal<E: TElement> : Sync {
data.restyle.hint.has_recascade_self();
}
// If the dirty descendants bit is set, we need to traverse no
// matter what. Skip examining the ElementData.
// If the dirty descendants bit is set, we need to traverse no matter
// what. Skip examining the ElementData.
if el.has_dirty_descendants() {
return true;
}
// Check the element data. If it doesn't exist, we need to visit
// the element.
// Check the element data. If it doesn't exist, we need to visit the
// element.
let data = match el.borrow_data() {
Some(d) => d,
None => return true,
@ -363,20 +371,20 @@ pub trait DomTraversal<E: TElement> : Sync {
return true;
}
// If we have a restyle hint or need to recascade, we need to
// visit the element.
// If we have a restyle hint or need to recascade, we need to visit the
// element.
//
// Note that this is different than checking has_current_styles(),
// since that can return true even if we have a restyle hint
// indicating that the element's descendants (but not necessarily
// the element) need restyling.
// since that can return true even if we have a restyle hint indicating
// that the element's descendants (but not necessarily the element) need
// restyling.
if !data.restyle.hint.is_empty() {
return true;
}
// Servo uses the post-order traversal for flow construction, so
// we need to traverse any element with damage so that we can perform
// fixup / reconstruction on our way back up the tree.
// Servo uses the post-order traversal for flow construction, so we need
// to traverse any element with damage so that we can perform fixup /
// reconstruction on our way back up the tree.
//
// We also need to traverse nodes with explicit damage and no other
// restyle data, so that this damage can be cleared.
@ -394,18 +402,23 @@ pub trait DomTraversal<E: TElement> : Sync {
///
/// This may be called multiple times when processing an element, so we pass
/// a parameter to keep the logs tidy.
fn should_traverse_children(&self,
thread_local: &mut ThreadLocalStyleContext<E>,
parent: E,
parent_data: &ElementData,
log: LogBehavior) -> bool
{
fn should_traverse_children(
&self,
thread_local: &mut ThreadLocalStyleContext<E>,
parent: E,
parent_data: &ElementData,
log: LogBehavior
) -> bool {
// See the comment on `cascade_node` for why we allow this on Gecko.
debug_assert!(cfg!(feature = "gecko") || parent.has_current_styles(parent_data));
debug_assert!(cfg!(feature = "gecko") ||
parent.has_current_styles(parent_data));
// If the parent computed display:none, we don't style the subtree.
if parent_data.styles.is_display_none() {
if log.allow() { debug!("Parent {:?} is display:none, culling traversal", parent); }
if log.allow() {
debug!("Parent {:?} is display:none, culling traversal",
parent);
}
return false;
}
@ -416,14 +429,13 @@ pub trait DomTraversal<E: TElement> : Sync {
// explicit children to an insertion point (or hide them entirely). It
// may also specify a scoped stylesheet, which changes the rules that
// apply within the subtree. These two effects can invalidate the result
// of property inheritance and selector matching (respectively) within the
// subtree.
// of property inheritance and selector matching (respectively) within
// the subtree.
//
// To avoid wasting work, we defer initial styling of XBL subtrees
// until frame construction, which does an explicit traversal of the
// unstyled children after shuffling the subtree. That explicit
// traversal may in turn find other bound elements, which get handled
// in the same way.
// To avoid wasting work, we defer initial styling of XBL subtrees until
// frame construction, which does an explicit traversal of the unstyled
// children after shuffling the subtree. That explicit traversal may in
// turn find other bound elements, which get handled in the same way.
//
// We explicitly avoid handling restyles here (explicitly removing or
// changing bindings), since that adds complexity and is rarer. If it
@ -432,7 +444,10 @@ pub trait DomTraversal<E: TElement> : Sync {
// an Element is changed.
if cfg!(feature = "gecko") && thread_local.is_initial_style() &&
parent_data.styles.primary().has_moz_binding() {
if log.allow() { debug!("Parent {:?} has XBL binding, deferring traversal", parent); }
if log.allow() {
debug!("Parent {:?} has XBL binding, deferring traversal",
parent);
}
return false;
}
@ -441,13 +456,24 @@ pub trait DomTraversal<E: TElement> : Sync {
/// Helper for the traversal implementations to select the children that
/// should be enqueued for processing.
fn traverse_children<F>(&self, thread_local: &mut Self::ThreadLocalContext, parent: E, mut f: F)
where F: FnMut(&mut Self::ThreadLocalContext, E::ConcreteNode)
fn traverse_children<F>(
&self,
thread_local: &mut Self::ThreadLocalContext,
parent: E,
mut f: F
)
where
F: FnMut(&mut Self::ThreadLocalContext, E::ConcreteNode)
{
// Check if we're allowed to traverse past this element.
let should_traverse =
self.should_traverse_children(thread_local.borrow_mut(), parent,
&parent.borrow_data().unwrap(), MayLog);
self.should_traverse_children(
thread_local.borrow_mut(),
parent,
&parent.borrow_data().unwrap(),
MayLog
);
thread_local.borrow_mut().end_element(parent);
if !should_traverse {
return;
@ -461,7 +487,7 @@ pub trait DomTraversal<E: TElement> : Sync {
if !self.shared_context().traversal_flags.for_reconstruct() {
let el = kid.as_element();
if el.as_ref().and_then(|el| el.borrow_data())
.map_or(false, |d| d.has_styles()) {
.map_or(false, |d| d.has_styles()) {
if self.shared_context().traversal_flags.for_animation_only() {
unsafe { parent.set_animation_only_dirty_descendants(); }
} else {
@ -474,9 +500,9 @@ pub trait DomTraversal<E: TElement> : Sync {
}
}
/// Ensures the existence of the ElementData, and returns it. This can't live
/// on TNode because of the trait-based separation between Servo's script
/// and layout crates.
/// Ensures the existence of the ElementData, and returns it. This can't
/// live on TNode because of the trait-based separation between Servo's
/// script and layout crates.
///
/// This is only safe to call in top-down traversal before processing the
/// children of |element|.
@ -504,9 +530,10 @@ pub trait DomTraversal<E: TElement> : Sync {
}
/// Helper for the function below.
fn resolve_style_internal<E, F>(context: &mut StyleContext<E>,
element: E, ensure_data: &F)
-> Option<E>
fn resolve_style_internal<E, F>(
context: &mut StyleContext<E>,
element: E, ensure_data: &F
) -> Option<E>
where E: TElement,
F: Fn(E),
{
@ -539,16 +566,18 @@ fn resolve_style_internal<E, F>(context: &mut StyleContext<E>,
context.thread_local.end_element(element);
if !context.shared.traversal_flags.for_default_styles() {
// Conservatively mark us as having dirty descendants, since there might
// be other unstyled siblings we miss when walking straight up the parent
// chain. No need to do this if we're computing default styles, since
// Conservatively mark us as having dirty descendants, since there
// might be other unstyled siblings we miss when walking straight up
// the parent chain.
//
// No need to do this if we're computing default styles, since
// resolve_default_style will want the tree to be left as it is.
unsafe { element.note_descendants::<DirtyDescendants>() };
}
}
// If we're display:none and none of our ancestors are, we're the root
// of a display:none subtree.
// If we're display:none and none of our ancestors are, we're the root of a
// display:none subtree.
if display_none_root.is_none() && data.styles.is_display_none() {
display_none_root = Some(element);
}
@ -557,8 +586,8 @@ fn resolve_style_internal<E, F>(context: &mut StyleContext<E>,
}
/// Manually resolve style by sequentially walking up the parent chain to the
/// first styled Element, ignoring pending restyles. The resolved style is
/// made available via a callback, and can be dropped by the time this function
/// first styled Element, ignoring pending restyles. The resolved style is made
/// available via a callback, and can be dropped by the time this function
/// returns in the display:none subtree case.
pub fn resolve_style<E, F, G, H>(context: &mut StyleContext<E>, element: E,
ensure_data: &F, clear_data: &G, callback: H)
@ -574,14 +603,15 @@ pub fn resolve_style<E, F, G, H>(context: &mut StyleContext<E>, element: E,
let display_none_root = resolve_style_internal(context, element, ensure_data);
// Make them available for the scope of the callback. The callee may use the
// argument, or perform any other processing that requires the styles to exist
// on the Element.
// argument, or perform any other processing that requires the styles to
// exist on the Element.
callback(&element.borrow_data().unwrap().styles);
// Clear any styles in display:none subtrees or subtrees not in the document,
// to leave the tree in a valid state. For display:none subtrees, we leave
// the styles on the display:none root, but for subtrees not in the document,
// we clear styles all the way up to the root of the disconnected subtree.
// Clear any styles in display:none subtrees or subtrees not in the
// document, to leave the tree in a valid state. For display:none subtrees,
// we leave the styles on the display:none root, but for subtrees not in the
// document, we clear styles all the way up to the root of the disconnected
// subtree.
let in_doc = element.as_node().is_in_doc();
if !in_doc || display_none_root.is_some() {
let mut curr = element;
@ -606,15 +636,18 @@ pub fn resolve_style<E, F, G, H>(context: &mut StyleContext<E>, element: E,
/// only taking into account user agent and user cascade levels. The resolved
/// style is made available via a callback, and will be dropped by the time this
/// function returns.
pub fn resolve_default_style<E, F, G, H>(context: &mut StyleContext<E>,
element: E,
ensure_data: &F,
set_data: &G,
callback: H)
where E: TElement,
F: Fn(E),
G: Fn(E, Option<ElementData>) -> Option<ElementData>,
H: FnOnce(&ElementStyles)
pub fn resolve_default_style<E, F, G, H>(
context: &mut StyleContext<E>,
element: E,
ensure_data: &F,
set_data: &G,
callback: H
)
where
E: TElement,
F: Fn(E),
G: Fn(E, Option<ElementData>) -> Option<ElementData>,
H: FnOnce(&ElementStyles),
{
// Save and clear out element data from the element and its ancestors.
let mut old_data: SmallVec<[(E, Option<ElementData>); 8]> = SmallVec::new();
@ -633,8 +666,8 @@ pub fn resolve_default_style<E, F, G, H>(context: &mut StyleContext<E>,
resolve_style_internal(context, element, ensure_data);
// Make them available for the scope of the callback. The callee may use the
// argument, or perform any other processing that requires the styles to exist
// on the Element.
// argument, or perform any other processing that requires the styles to
// exist on the Element.
callback(&element.borrow_data().unwrap().styles);
// Swap the old element data back into the element and its ancestors.
@ -646,13 +679,16 @@ pub fn resolve_default_style<E, F, G, H>(context: &mut StyleContext<E>,
/// Calculates the style for a single node.
#[inline]
#[allow(unsafe_code)]
pub fn recalc_style_at<E, D>(traversal: &D,
traversal_data: &PerLevelTraversalData,
context: &mut StyleContext<E>,
element: E,
data: &mut ElementData)
where E: TElement,
D: DomTraversal<E>
pub fn recalc_style_at<E, D>(
traversal: &D,
traversal_data: &PerLevelTraversalData,
context: &mut StyleContext<E>,
element: E,
data: &mut ElementData
)
where
E: TElement,
D: DomTraversal<E>,
{
context.thread_local.begin_element(element, data);
context.thread_local.statistics.elements_traversed += 1;
@ -662,7 +698,8 @@ pub fn recalc_style_at<E, D>(traversal: &D,
let compute_self = !element.has_current_styles(data);
let mut hint = RestyleHint::empty();
debug!("recalc_style_at: {:?} (compute_self={:?}, dirty_descendants={:?}, data={:?})",
debug!("recalc_style_at: {:?} (compute_self={:?}, \
dirty_descendants={:?}, data={:?})",
element, compute_self, element.has_dirty_descendants(), data);
// Compute style for this element if necessary.
@ -677,8 +714,8 @@ pub fn recalc_style_at<E, D>(traversal: &D,
ChildCascadeRequirement::CanSkipCascade => {}
};
// We must always cascade native anonymous subtrees, since they inherit styles
// from their first non-NAC ancestor.
// We must always cascade native anonymous subtrees, since they inherit
// styles from their first non-NAC ancestor.
if element.is_native_anonymous() {
hint |= RECASCADE_SELF;
}
@ -725,12 +762,14 @@ pub fn recalc_style_at<E, D>(traversal: &D,
// Preprocess children, propagating restyle hints and handling sibling
// relationships.
if traversal.should_traverse_children(&mut context.thread_local,
element,
&data,
DontLog) &&
(has_dirty_descendants_for_this_restyle ||
!propagated_hint.is_empty()) {
let should_traverse_children = traversal.should_traverse_children(
&mut context.thread_local,
element,
&data,
DontLog
);
if should_traverse_children &&
(has_dirty_descendants_for_this_restyle || !propagated_hint.is_empty()) {
let reconstructed_ancestor =
data.restyle.reconstructed_self_or_ancestor();
@ -753,36 +792,37 @@ pub fn recalc_style_at<E, D>(traversal: &D,
unsafe { element.unset_animation_only_dirty_descendants(); }
}
// There are two cases when we want to clear the dity descendants bit
// here after styling this element.
// There are two cases when we want to clear the dity descendants bit here
// after styling this element.
//
// The first case is when this element is the root of a display:none
// subtree, even if the style didn't change (since, if the style did
// change, we'd have already cleared it above).
// subtree, even if the style didn't change (since, if the style did change,
// we'd have already cleared it above).
//
// This keeps the tree in a valid state without requiring the DOM to
// check display:none on the parent when inserting new children (which
// can be moderately expensive). Instead, DOM implementations can
// unconditionally set the dirty descendants bit on any styled parent,
// and let the traversal sort it out.
// This keeps the tree in a valid state without requiring the DOM to check
// display:none on the parent when inserting new children (which can be
// moderately expensive). Instead, DOM implementations can unconditionally
// set the dirty descendants bit on any styled parent, and let the traversal
// sort it out.
//
// The second case is when we are in a restyle for reconstruction,
// where we won't need to perform a post-traversal to pick up any
// change hints.
// The second case is when we are in a restyle for reconstruction, where we
// won't need to perform a post-traversal to pick up any change hints.
if data.styles.is_display_none() ||
context.shared.traversal_flags.for_reconstruct() {
unsafe { element.unset_dirty_descendants(); }
}
}
fn compute_style<E, D>(_traversal: &D,
traversal_data: &PerLevelTraversalData,
context: &mut StyleContext<E>,
element: E,
data: &mut ElementData)
-> ChildCascadeRequirement
where E: TElement,
D: DomTraversal<E>,
fn compute_style<E, D>(
_traversal: &D,
traversal_data: &PerLevelTraversalData,
context: &mut StyleContext<E>,
element: E,
data: &mut ElementData
) -> ChildCascadeRequirement
where
E: TElement,
D: DomTraversal<E>,
{
use data::RestyleKind::*;
use sharing::StyleSharingResult::*;
@ -830,9 +870,8 @@ fn compute_style<E, D>(_traversal: &D,
}
CascadeWithReplacements(flags) => {
// Skipping full matching, load cascade inputs from previous values.
context.thread_local.current_element_info
.as_mut().unwrap()
.cascade_inputs = ElementCascadeInputs::new_from_element_data(data);
*context.cascade_inputs_mut() =
ElementCascadeInputs::new_from_element_data(data);
let important_rules_changed = element.replace_rules(flags, context);
element.cascade_primary_and_pseudos(
context,
@ -842,9 +881,8 @@ fn compute_style<E, D>(_traversal: &D,
}
CascadeOnly => {
// Skipping full matching, load cascade inputs from previous values.
context.thread_local.current_element_info
.as_mut().unwrap()
.cascade_inputs = ElementCascadeInputs::new_from_element_data(data);
*context.cascade_inputs_mut() =
ElementCascadeInputs::new_from_element_data(data);
element.cascade_primary_and_pseudos(
context,
data,
@ -904,12 +942,21 @@ where
}
/// Clear style data for all the subtree under `el`.
pub fn clear_descendant_data<E: TElement, F: Fn(E)>(el: E, clear_data: &F) {
pub fn clear_descendant_data<E, F>(
el: E,
clear_data: &F
)
where
E: TElement,
F: Fn(E),
{
for kid in el.as_node().traversal_children() {
if let Some(kid) = kid.as_element() {
// We maintain an invariant that, if an element has data, all its ancestors
// have data as well. By consequence, any element without data has no
// descendants with data.
// We maintain an invariant that, if an element has data, all its
// ancestors have data as well.
//
// By consequence, any element without data has no descendants with
// data.
if kid.get_data().is_some() {
clear_data(kid);
clear_descendant_data(kid, clear_data);