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Bug 1330375 - P2: Reduce layout flushes in nsGenericHTMLElement::GetInnerText. r=emilio,heycam

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Instead of unconditionally flushing layout, flush style and skip flush
layout unless any frame state bits on the element, or ancestors,
indicate that a flush is required.

MozReview-Commit-ID: 4zaB1eaE0fm

--HG--
extra : rebase_source : a02b014e127f8fc3e27afedb2012e09a7e8905b8
This commit is contained in:
Dan Glastonbury 2018-07-19 14:26:46 +10:00
parent 165882c3b0
commit 19dd66bbb1
1 changed files with 57 additions and 10 deletions
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67
dom/html/nsGenericHTMLElement.cpp
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@ -2901,7 +2901,7 @@ nsGenericHTMLElement::NewURIFromString(const nsAString& aURISpec,
}
static bool
IsOrHasAncestorWithDisplayNone(Element* aElement, nsIPresShell* aPresShell)
IsOrHasAncestorWithDisplayNone(Element* aElement)
{
return !aElement->HasServoData() || Servo_Element_IsDisplayNone(aElement);
}
@ -2910,18 +2910,65 @@ void
nsGenericHTMLElement::GetInnerText(mozilla::dom::DOMString& aValue,
mozilla::ErrorResult& aError)
{
if (!GetPrimaryFrame(FlushType::Layout)) {
nsIPresShell* presShell = nsContentUtils::GetPresShellForContent(this);
// NOTE(emilio): We need to check the presshell is initialized in order to
// ensure the document is styled.
if (!presShell || !presShell->DidInitialize() ||
IsOrHasAncestorWithDisplayNone(this, presShell)) {
GetTextContentInternal(aValue, aError);
return;
// innerText depends on layout. For example, white space processing is
// something that happens during reflow and which must be reflected by
// innerText. So for:
//
// <div style="white-space:normal"> A B C </div>
//
// innerText should give "A B C".
//
// The approach taken here to avoid the expense of reflow is to flush style
// and then see whether it's necessary to flush layout afterwards. Flushing
// layout can be skipped if we can detect that the element or its descendants
// are not dirty.
// Obtain the composed doc to handle elements in Shadow DOM.
nsIDocument* doc = GetComposedDoc();
if (doc) {
doc->FlushPendingNotifications(FlushType::Style);
}
// Elements with `display: content` will not have a frame. To handle Shadow
// DOM, walk the flattened tree looking for parent frame.
nsIFrame* frame = GetPrimaryFrame();
if (IsDisplayContents()) {
for (Element* parent = GetFlattenedTreeParentElement();
parent;
parent = parent->GetFlattenedTreeParentElement())
{
frame = parent->GetPrimaryFrame();
if (frame) {
break;
}
}
}
nsRange::GetInnerTextNoFlush(aValue, aError, this);
// Check for dirty reflow roots in the subtree from targetFrame; this requires
// a reflow flush.
bool dirty = frame && frame->PresShell()->FrameIsAncestorOfDirtyRoot(frame);
// The way we do that is by checking whether the element has either of the two
// dirty bits (NS_FRAME_IS_DIRTY or NS_FRAME_HAS_DIRTY_DESCENDANTS) or if any
// ancestor has NS_FRAME_IS_DIRTY. We need to check for NS_FRAME_IS_DIRTY on
// ancestors since that is something that implies NS_FRAME_IS_DIRTY on all
// descendants.
dirty |= frame && frame->HasAnyStateBits(NS_FRAME_HAS_DIRTY_CHILDREN);
while (!dirty && frame) {
dirty |= frame->HasAnyStateBits(NS_FRAME_IS_DIRTY);
frame = frame->GetInFlowParent();
}
// Flush layout if we determined a reflow is required.
if (dirty && doc) {
doc->FlushPendingNotifications(FlushType::Layout);
}
if (IsOrHasAncestorWithDisplayNone(this)) {
GetTextContentInternal(aValue, aError);
} else {
nsRange::GetInnerTextNoFlush(aValue, aError, this);
}
}
void