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Bug 1779645 Part 1 - Switch CSS named page fragmentation to happen at reflow instead of frame construction r=dholbert

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This also adds a small post-processing step for frame-construction to ensure
that replaced frames (or more generally frames with content but no children)
have the auto page-name set on them.

When page-name value tracking is switched to be lazy, this post-processing step
will likely be redundant and can be removed.

Differential Revision: https://phabricator.services.mozilla.com/D152701
This commit is contained in:
Emily McDonough
2022-09-12 22:44:48 +00:00
parent 334a736b2a
commit e114010ff0
3 changed files with 152 additions and 83 deletions
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159
layout/base/nsCSSFrameConstructor.cpp
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@@ -5502,89 +5502,13 @@ void nsCSSFrameConstructor::AddFrameConstructionItemsInternal(
return;
}
bool pageNameBreak = false;
// TODO: We should document why the TextIsOnlyWhitespace() check is needed.
// This will be documented as part of fixing Bug 1782324
if (aParentFrame && aState.mPresContext->IsPaginated() &&
StaticPrefs::layout_css_named_pages_enabled() &&
!aContent->TextIsOnlyWhitespace()) {
// TODO: This is slightly incorrect! See Bug 1764437
// We should be waiting all of our descendent frames to be constructed.
//
// Alternatively, we could propagate this back up the frame tree after
// constructing this frame's first child, inspecting the parent frames and
// rewriting their first child page-name.
const StylePageName& pageName = aComputedStyle->StylePage()->mPage;
// Resolve auto against the parent frame's used page name, which has been
// determined and set on aState.mAutoPageNameValue. If this item is not
// block-level then we use the value that auto resolves to.
//
// This is to achieve the propagation behavior described in the spec:
//
// "A start page value and end page value is determined for each box as
// the value (if any) propagated from its first or last child box
// (respectively), else the used value on the box itself."
//
// "A child propagates its own start or end page value if and only if the
// page property applies to it."
//
// The page property only applies to "boxes that create class A break
// points". When taken together, means that non block-level children do
// not propagate start/end page values, and instead we use "the used
// value on the box itself", the "box itself" being aParentFrame. This
// value has been determined and saved as aState.mAutoPageNameValue
//
// https://www.w3.org/TR/css-page-3/#using-named-pages
// https://www.w3.org/TR/css-break-3/#btw-blocks
const nsAtom* const pageNameAtom =
(pageName.IsPageName() &&
aComputedStyle->StyleDisplay()->IsBlockOutsideStyle())
? pageName.AsPageName().AsAtom()
: aState.mAutoPageNameValue;
// Check if we are the first child of our parent. If so, propagate this
// child's page name up the frame tree for every frame while our ancestor
// is the first child of its parent.
nsIFrame::PageValues* const framePageValues =
aParentFrame->GetProperty(nsIFrame::PageValuesProperty());
// TODO alaskanemily: This assert should be removed when we move to lazily
// setting the PageValuesProperty
MOZ_ASSERT(framePageValues,
"child box page names should have been created by "
"AutoFrameConstructionPageName");
if (!framePageValues->mStartPageValue) {
framePageValues->mStartPageValue = pageNameAtom;
if (nsIFrame* const prevFrame = aParentFrame->GetPrevSibling()) {
const nsIFrame::PageValues* const prevPageValues =
prevFrame->GetProperty(nsIFrame::PageValuesProperty());
if (prevPageValues && prevPageValues->mEndPageValue != pageNameAtom) {
pageNameBreak = true;
}
}
// Propagate the start page value back up the frame tree.
// If the frame already has mStartPageValue set, then we are not a
// descendant of the frame's first child.
for (nsContainerFrame* frame = aParentFrame->GetParent(); frame;
frame = frame->GetParent()) {
nsIFrame::PageValues* const parentPageValues =
frame->GetProperty(nsIFrame::PageValuesProperty());
if (!parentPageValues || parentPageValues->mStartPageValue) {
break;
}
parentPageValues->mStartPageValue = pageNameAtom;
}
}
framePageValues->mEndPageValue = pageNameAtom;
}
const bool canHavePageBreak =
aFlags.contains(ItemFlag::AllowPageBreak) &&
aState.mPresContext->IsPaginated() &&
!display.IsAbsolutelyPositionedStyle() &&
!(aParentFrame && aParentFrame->IsGridContainerFrame()) &&
!(bits & FCDATA_IS_TABLE_PART) && !(bits & FCDATA_IS_SVG_TEXT);
if (canHavePageBreak && (pageNameBreak || display.BreakBefore())) {
if (canHavePageBreak && display.BreakBefore()) {
AppendPageBreakItem(aContent, aItems);
}
@@ -9626,6 +9550,87 @@ inline void nsCSSFrameConstructor::ConstructFramesFromItemList(
VerifyGridFlexContainerChildren(aParentFrame, aFrameList);
// Calculate and propagate page-name values for each frame in the frame list.
// This will be affected by https://bugzilla.mozilla.org/1782597
if (aState.mPresContext->IsPaginated() &&
StaticPrefs::layout_css_named_pages_enabled()) {
// Set the start/end page values while iterating the frame list, to walk
// up the frame tree only once after iterating the frame list.
// This also avoids extra property lookups on these frames.
const nsAtom* startPageValue = nullptr;
const nsAtom* endPageValue = nullptr;
for (nsIFrame* f : aFrameList) {
// Resolve auto against the parent frame's used page name, which has been
// determined and set on aState.mAutoPageNameValue. If this item is not
// block-level then we use the value that auto resolves to.
//
// This is to achieve the propagation behavior described in the spec:
//
// "A start page value and end page value is determined for each box as
// the value (if any) propagated from its first or last child box
// (respectively), else the used value on the box itself."
//
// "A child propagates its own start or end page value if and only if the
// page property applies to it."
//
// The page property only applies to "boxes that create class A break
// points". When taken together, this means that non block-level children
// do not propagate start/end page values, and instead we use "the used
// value on the box itself", the "box itself" being aParentFrame. This
// value has been determined and saved as aState.mAutoPageNameValue
//
// https://www.w3.org/TR/css-page-3/#using-named-pages
// https://www.w3.org/TR/css-break-3/#btw-blocks
const StylePageName& pageName = f->StylePage()->mPage;
const nsAtom* const pageNameAtom =
(pageName.IsPageName() && f->IsBlockOutside())
? pageName.AsPageName().AsAtom()
: aState.mAutoPageNameValue;
nsIFrame::PageValues* pageValues =
f->GetProperty(nsIFrame::PageValuesProperty());
if (!pageValues) {
pageValues = new nsIFrame::PageValues();
f->AddProperty(nsIFrame::PageValuesProperty(), pageValues);
}
MOZ_ASSERT(!pageValues->mStartPageValue == !pageValues->mEndPageValue,
"Both or neither mStartPageValue and mEndPageValue should "
"have been set");
if (!pageValues->mStartPageValue) {
pageValues->mStartPageValue = pageNameAtom;
pageValues->mEndPageValue = pageNameAtom;
}
if (!startPageValue) {
startPageValue = pageValues->mStartPageValue;
}
endPageValue = pageValues->mEndPageValue;
}
MOZ_ASSERT(!startPageValue == !endPageValue,
"Should have set both or neither page values");
if (startPageValue) {
// TODO: This is slightly incorrect! See Bug 1764437
// We should be waiting all of our descendent frames to be constructed.
//
// Alternatively, we could propagate this back up the frame tree after
// constructing this frame's first child, inspecting the parent frames
// and rewriting their first child page-name.
for (nsContainerFrame* frame = aParentFrame; frame;
frame = frame->GetParent()) {
nsIFrame::PageValues* const parentPageValues =
frame->GetProperty(nsIFrame::PageValuesProperty());
// Propagate the start page value back up the frame tree.
// If the frame already has mStartPageValue set, then we are not a
// descendant of the frame's first child.
if (!parentPageValues) {
break;
}
if (!parentPageValues->mStartPageValue) {
parentPageValues->mStartPageValue = startPageValue;
}
parentPageValues->mEndPageValue = endPageValue;
}
}
}
if (aParentIsWrapperAnonBox) {
for (nsIFrame* f : aFrameList) {
f->SetParentIsWrapperAnonBox();