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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
/* rendering object for CSS :first-letter pseudo-element */
#include "nsFirstLetterFrame.h"
#include "nsPresContext.h"
#include "nsPresContextInlines.h"
#include "mozilla/ComputedStyle.h"
#include "mozilla/PresShell.h"
#include "mozilla/PresShellInlines.h"
#include "mozilla/RestyleManager.h"
#include "mozilla/ServoStyleSet.h"
#include "mozilla/StaticPrefs_layout.h"
#include "nsIContent.h"
#include "nsLayoutUtils.h"
#include "nsLineLayout.h"
#include "nsGkAtoms.h"
#include "nsFrameManager.h"
#include "nsPlaceholderFrame.h"
#include "nsTextFrame.h"
#include "nsCSSFrameConstructor.h"
using namespace mozilla;
using namespace mozilla::layout;
nsFirstLetterFrame* NS_NewFirstLetterFrame(PresShell* aPresShell,
ComputedStyle* aStyle) {
return new (aPresShell)
nsFirstLetterFrame(aStyle, aPresShell->GetPresContext());
nsFirstLetterFrame* NS_NewFloatingFirstLetterFrame(PresShell* aPresShell,
ComputedStyle* aStyle) {
return new (aPresShell)
nsFloatingFirstLetterFrame(aStyle, aPresShell->GetPresContext());
nsresult nsFirstLetterFrame::GetFrameName(nsAString& aResult) const {
return MakeFrameName(u"Letter"_ns, aResult);
void nsFirstLetterFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
const nsDisplayListSet& aLists) {
BuildDisplayListForInline(aBuilder, aLists);
void nsFirstLetterFrame::Init(nsIContent* aContent, nsContainerFrame* aParent,
nsIFrame* aPrevInFlow) {
RefPtr<ComputedStyle> newSC;
if (aPrevInFlow) {
// Get proper ComputedStyle for ourselves. We're creating the frame
// that represents everything *except* the first letter, so just create
// a ComputedStyle that inherits from our style parent, with no extra rules.
nsIFrame* styleParent =
CorrectStyleParentFrame(aParent, PseudoStyleType::firstLetter);
ComputedStyle* parentComputedStyle = styleParent->Style();
newSC = PresContext()->StyleSet()->ResolveStyleForFirstLetterContinuation(
nsContainerFrame::Init(aContent, aParent, aPrevInFlow);
void nsFirstLetterFrame::SetInitialChildList(ChildListID aListID,
nsFrameList&& aChildList) {
MOZ_ASSERT(aListID == FrameChildListID::Principal,
"Principal child list is the only "
"list that nsFirstLetterFrame should set via this function");
for (nsIFrame* f : aChildList) {
MOZ_ASSERT(f->GetParent() == this, "Unexpected parent");
"We should not have kids that are containers!");
nsLayoutUtils::MarkDescendantsDirty(f); // Drops cached textruns
mFrames = std::move(aChildList);
nsresult nsFirstLetterFrame::GetChildFrameContainingOffset(
int32_t inContentOffset, bool inHint, int32_t* outFrameContentOffset,
nsIFrame** outChildFrame) {
nsIFrame* kid = mFrames.FirstChild();
if (kid) {
return kid->GetChildFrameContainingOffset(
inContentOffset, inHint, outFrameContentOffset, outChildFrame);
return nsIFrame::GetChildFrameContainingOffset(
inContentOffset, inHint, outFrameContentOffset, outChildFrame);
// Needed for non-floating first-letter frames and for the continuations
// following the first-letter that we also use nsFirstLetterFrame for.
/* virtual */
void nsFirstLetterFrame::AddInlineMinISize(
gfxContext* aRenderingContext, nsIFrame::InlineMinISizeData* aData) {
DoInlineMinISize(aRenderingContext, aData);
// Needed for non-floating first-letter frames and for the continuations
// following the first-letter that we also use nsFirstLetterFrame for.
/* virtual */
void nsFirstLetterFrame::AddInlinePrefISize(
gfxContext* aRenderingContext, nsIFrame::InlinePrefISizeData* aData) {
DoInlinePrefISize(aRenderingContext, aData);
// Needed for floating first-letter frames.
/* virtual */
nscoord nsFirstLetterFrame::GetMinISize(gfxContext* aRenderingContext) {
return nsLayoutUtils::MinISizeFromInline(this, aRenderingContext);
// Needed for floating first-letter frames.
/* virtual */
nscoord nsFirstLetterFrame::GetPrefISize(gfxContext* aRenderingContext) {
return nsLayoutUtils::PrefISizeFromInline(this, aRenderingContext);
/* virtual */
nsIFrame::SizeComputationResult nsFirstLetterFrame::ComputeSize(
gfxContext* aRenderingContext, WritingMode aWM, const LogicalSize& aCBSize,
nscoord aAvailableISize, const LogicalSize& aMargin,
const LogicalSize& aBorderPadding, const StyleSizeOverrides& aSizeOverrides,
ComputeSizeFlags aFlags) {
if (GetPrevInFlow()) {
// We're wrapping the text *after* the first letter, so behave like an
// inline frame.
return nsContainerFrame::ComputeSize(aRenderingContext, aWM, aCBSize,
aAvailableISize, aMargin, aBorderPadding,
aSizeOverrides, aFlags);
bool nsFirstLetterFrame::UseTightBounds() const {
int v = StaticPrefs::layout_css_floating_first_letter_tight_glyph_bounds();
// Check for the simple cases:
// pref value > 0: use legacy gecko behavior
// pref value = 0: use webkit/blink-like behavior
if (v > 0) {
return true;
if (v == 0) {
return false;
// Pref value < 0: use heuristics to determine whether the page is assuming
// webkit/blink-style behavior:
// If line-height is less than font-size, or there is a negative block-start
// or -end margin, use webkit/blink behavior.
if (nsTextFrame* textFrame = do_QueryFrame(mFrames.FirstChild())) {
RefPtr<nsFontMetrics> fm = textFrame->InflatedFontMetrics();
if (textFrame->ComputeLineHeight() < fm->EmHeight()) {
return false;
const auto wm = GetWritingMode();
const auto& margin = StyleMargin()->mMargin;
const auto& bStart = margin.GetBStart(wm);
// Currently, we only check for margins with negative *length* values;
// negative percentages seem unlikely to be used/useful in this context.
if (bStart.ConvertsToLength() && bStart.ToLength() < 0) {
return false;
const auto& bEnd = margin.GetBEnd(wm);
if (bEnd.ConvertsToLength() && bEnd.ToLength() < 0) {
return false;
return true;
void nsFirstLetterFrame::Reflow(nsPresContext* aPresContext,
ReflowOutput& aMetrics,
const ReflowInput& aReflowInput,
nsReflowStatus& aReflowStatus) {
"Caller should pass a fresh reflow status!");
// Grab overflow list
nsIFrame* kid = mFrames.FirstChild();
// Setup reflow input for our child
WritingMode wm = aReflowInput.GetWritingMode();
LogicalSize availSize = aReflowInput.AvailableSize();
const auto bp = aReflowInput.ComputedLogicalBorderPadding(wm);
"should no longer use unconstrained inline size");
availSize.ISize(wm) -= bp.IStartEnd(wm);
if (NS_UNCONSTRAINEDSIZE != availSize.BSize(wm)) {
availSize.BSize(wm) -= bp.BStartEnd(wm);
WritingMode lineWM = aMetrics.GetWritingMode();
ReflowOutput kidMetrics(lineWM);
// Reflow the child
if (!aReflowInput.mLineLayout) {
// When there is no lineLayout provided, we provide our own. The
// only time that the first-letter-frame is not reflowing in a
// line context is when its floating.
WritingMode kidWritingMode = WritingModeForLine(wm, kid);
LogicalSize kidAvailSize = availSize.ConvertTo(kidWritingMode, wm);
ReflowInput rs(aPresContext, aReflowInput, kid, kidAvailSize);
nsLineLayout ll(aPresContext, nullptr, aReflowInput, nullptr, nullptr);
bp.IStart(wm), bp.BStart(wm), availSize.ISize(wm), NS_UNCONSTRAINEDSIZE,
false, true, kidWritingMode,
nsSize(aReflowInput.AvailableWidth(), aReflowInput.AvailableHeight()));
rs.mLineLayout = &ll;
kid->Reflow(aPresContext, kidMetrics, rs, aReflowStatus);
// In the floating first-letter case, we need to set this ourselves;
// nsLineLayout::BeginSpan will set it in the other case
mBaseline = kidMetrics.BlockStartAscent();
// Place and size the child and update the output metrics
LogicalSize convertedSize = kidMetrics.Size(wm);
const bool tightBounds = UseTightBounds();
const nscoord shift =
tightBounds ? 0
// Shift by half of the difference between the line-height
// we're going to use and current height of the kid frame.
: (rs.GetLineHeight() - convertedSize.BSize(wm)) / 2;
kid->SetRect(nsRect(bp.IStart(wm), bp.BStart(wm) + shift,
convertedSize.ISize(wm), convertedSize.BSize(wm)));
kid->FinishAndStoreOverflow(&kidMetrics, rs.mStyleDisplay);
kid->DidReflow(aPresContext, nullptr);
if (!tightBounds) {
// Adjust size to account for line-height.
convertedSize.BSize(wm) = rs.GetLineHeight();
convertedSize.ISize(wm) += bp.IStartEnd(wm);
convertedSize.BSize(wm) += bp.BStartEnd(wm);
aMetrics.SetSize(wm, convertedSize);
aMetrics.SetBlockStartAscent(kidMetrics.BlockStartAscent() + bp.BStart(wm));
// Ensure that the overflow rect contains the child textframe's
// overflow rect.
// Note that if this is floating, the overline/underline drawable
// area is in the overflow rect of the child textframe.
ConsiderChildOverflow(aMetrics.mOverflowAreas, kid);
FinishAndStoreOverflow(&aMetrics, aReflowInput.mStyleDisplay);
} else {
// Pretend we are a span and reflow the child frame
nsLineLayout* ll = aReflowInput.mLineLayout;
bool pushedFrame;
ll->SetInFirstLetter(Style()->GetPseudoType() ==
ll->BeginSpan(this, &aReflowInput, bp.IStart(wm), availSize.ISize(wm),
ll->ReflowFrame(kid, aReflowStatus, &kidMetrics, pushedFrame);
NS_ASSERTION(lineWM.IsVertical() == wm.IsVertical(),
"we're assuming we can mix sizes between lineWM and wm "
"since we shouldn't have orthogonal writing modes within "
"a line.");
aMetrics.ISize(lineWM) = ll->EndSpan(this) + bp.IStartEnd(wm);
if (mComputedStyle->StyleTextReset()->mInitialLetterSize != 0.0f) {
aMetrics.SetBlockStartAscent(kidMetrics.BlockStartAscent() +
aMetrics.BSize(lineWM) = kidMetrics.BSize(lineWM) + bp.BStartEnd(wm);
} else {
nsLayoutUtils::SetBSizeFromFontMetrics(this, aMetrics, bp, lineWM, wm);
if (!aReflowStatus.IsInlineBreakBefore()) {
// Create a continuation or remove existing continuations based on
// the reflow completion status.
if (aReflowStatus.IsComplete()) {
if (aReflowInput.mLineLayout) {
if (nsIFrame* kidNextInFlow = kid->GetNextInFlow()) {
DestroyContext context(PresShell());
// Remove all of the childs next-in-flows
kidNextInFlow, true);
} else {
// Create a continuation for the child frame if it doesn't already
// have one.
if (!IsFloating()) {
// And then push it to our overflow list
nsFrameList overflow = mFrames.TakeFramesAfter(kid);
if (overflow.NotEmpty()) {
} else if (!kid->GetNextInFlow()) {
// For floating first letter frames (if a continuation wasn't already
// created for us) we need to put the continuation with the rest of the
// text that the first letter frame was made out of.
nsIFrame* continuation;
CreateContinuationForFloatingParent(kid, &continuation, true);
/* virtual */
bool nsFirstLetterFrame::CanContinueTextRun() const {
// We can continue a text run through a first-letter frame.
return true;
void nsFirstLetterFrame::CreateContinuationForFloatingParent(
nsIFrame* aChild, nsIFrame** aContinuation, bool aIsFluid) {
"can only call this on floating first letter frames");
MOZ_ASSERT(aContinuation, "bad args");
*aContinuation = nullptr;
mozilla::PresShell* presShell = PresShell();
nsPlaceholderFrame* placeholderFrame = GetPlaceholderFrame();
nsContainerFrame* parent = placeholderFrame->GetParent();
nsIFrame* continuation = presShell->FrameConstructor()->CreateContinuingFrame(
aChild, parent, aIsFluid);
// The continuation will have gotten the first letter style from its
// prev continuation, so we need to repair the ComputedStyle so it
// doesn't have the first letter styling.
// Note that getting parent frame's ComputedStyle is different from getting
// this frame's ComputedStyle's parent in the presence of ::first-line,
// which we do want the continuation to inherit from.
ComputedStyle* parentSC = parent->Style();
if (parentSC) {
RefPtr<ComputedStyle> newSC;
newSC =
// XXX Bidi may not be involved but we have to use the list name
// FrameChildListID::NoReflowPrincipal because this is just like creating a
// continuation except we have to insert it in a different place and we don't
// want a reflow command to try to be issued.
parent->InsertFrames(FrameChildListID::NoReflowPrincipal, placeholderFrame,
nullptr, nsFrameList(continuation, continuation));
*aContinuation = continuation;
void nsFirstLetterFrame::DrainOverflowFrames(nsPresContext* aPresContext) {
// Check for an overflow list with our prev-in-flow
nsFirstLetterFrame* prevInFlow = (nsFirstLetterFrame*)GetPrevInFlow();
if (prevInFlow) {
AutoFrameListPtr overflowFrames(aPresContext,
if (overflowFrames) {
NS_ASSERTION(mFrames.IsEmpty(), "bad overflow list");
// When pushing and pulling frames we need to check for whether any
// views need to be reparented.
nsContainerFrame::ReparentFrameViewList(*overflowFrames, prevInFlow,
mFrames.InsertFrames(this, nullptr, std::move(*overflowFrames));
// It's also possible that we have an overflow list for ourselves
AutoFrameListPtr overflowFrames(aPresContext, StealOverflowFrames());
if (overflowFrames) {
NS_ASSERTION(mFrames.NotEmpty(), "overflow list w/o frames");
mFrames.AppendFrames(nullptr, std::move(*overflowFrames));
// Now repair our first frames ComputedStyle (since we only reflow
// one frame there is no point in doing any other ones until they
// are reflowed)
nsIFrame* kid = mFrames.FirstChild();
if (kid) {
nsIContent* kidContent = kid->GetContent();
if (kidContent) {
NS_ASSERTION(kidContent->IsText(), "should contain only text nodes");
ComputedStyle* parentSC;
if (prevInFlow) {
// This is for the rest of the content not in the first-letter.
nsIFrame* styleParent =
CorrectStyleParentFrame(GetParent(), PseudoStyleType::firstLetter);
parentSC = styleParent->Style();
} else {
// And this for the first-letter style.
parentSC = mComputedStyle;
RefPtr<ComputedStyle> sc =
aPresContext->StyleSet()->ResolveStyleForText(kidContent, parentSC);
Maybe<nscoord> nsFirstLetterFrame::GetNaturalBaselineBOffset(
WritingMode aWM, BaselineSharingGroup aBaselineGroup,
BaselineExportContext) const {
if (aBaselineGroup == BaselineSharingGroup::Last) {
return Nothing{};
return Some(mBaseline);
LogicalSides nsFirstLetterFrame::GetLogicalSkipSides() const {
if (GetPrevContinuation()) {
// We shouldn't get calls to GetSkipSides for later continuations since
// they have separate ComputedStyles with initial values for all the
// properties that could trigger a call to GetSkipSides. Then again,
// it's not really an error to call GetSkipSides on any frame, so
// that's why we handle it properly.
return LogicalSides(mWritingMode, eLogicalSideBitsAll);
return LogicalSides(mWritingMode); // first continuation displays all sides