Source code

Revision control

Copy as Markdown

Other Tools

/* -*- 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 HTML <br> elements */
#include "mozilla/CaretAssociationHint.h"
#include "mozilla/PresShell.h"
#include "mozilla/dom/HTMLBRElement.h"
#include "gfxContext.h"
#include "nsCOMPtr.h"
#include "nsContainerFrame.h"
#include "nsFontMetrics.h"
#include "nsHTMLParts.h"
#include "nsIFrame.h"
#include "nsPresContext.h"
#include "nsLineLayout.h"
#include "nsStyleConsts.h"
#include "nsGkAtoms.h"
#include "nsLayoutUtils.h"
#include "nsIContent.h"
using namespace mozilla;
namespace mozilla {
class BRFrame final : public nsIFrame {
friend nsIFrame* ::NS_NewBRFrame(mozilla::PresShell* aPresShell,
ComputedStyle* aStyle);
ContentOffsets CalcContentOffsetsFromFramePoint(
const nsPoint& aPoint) override;
FrameSearchResult PeekOffsetNoAmount(bool aForward,
int32_t* aOffset) override;
FrameSearchResult PeekOffsetCharacter(
bool aForward, int32_t* aOffset,
PeekOffsetCharacterOptions aOptions =
PeekOffsetCharacterOptions()) override;
FrameSearchResult PeekOffsetWord(bool aForward, bool aWordSelectEatSpace,
bool aIsKeyboardSelect, int32_t* aOffset,
PeekWordState* aState,
bool aTrimSpaces) override;
void Reflow(nsPresContext* aPresContext, ReflowOutput& aMetrics,
const ReflowInput& aReflowInput,
nsReflowStatus& aStatus) override;
void AddInlineMinISize(gfxContext* aRenderingContext,
InlineMinISizeData* aData) override;
void AddInlinePrefISize(gfxContext* aRenderingContext,
InlinePrefISizeData* aData) override;
nscoord GetMinISize(gfxContext* aRenderingContext) override;
nscoord GetPrefISize(gfxContext* aRenderingContext) override;
Maybe<nscoord> GetNaturalBaselineBOffset(
WritingMode aWM, BaselineSharingGroup aBaselineGroup,
BaselineExportContext) const override;
mozilla::a11y::AccType AccessibleType() override;
nsresult GetFrameName(nsAString& aResult) const override {
return MakeFrameName(u"BR"_ns, aResult);
BRFrame(ComputedStyle* aStyle, nsPresContext* aPresContext)
: nsIFrame(aStyle, aPresContext, kClassID),
virtual ~BRFrame();
nscoord mAscent;
} // namespace mozilla
nsIFrame* NS_NewBRFrame(mozilla::PresShell* aPresShell, ComputedStyle* aStyle) {
return new (aPresShell) BRFrame(aStyle, aPresShell->GetPresContext());
BRFrame::~BRFrame() = default;
void BRFrame::Reflow(nsPresContext* aPresContext, ReflowOutput& aMetrics,
const ReflowInput& aReflowInput, nsReflowStatus& aStatus) {
MOZ_ASSERT(aStatus.IsEmpty(), "Caller should pass a fresh reflow status!");
WritingMode wm = aReflowInput.GetWritingMode();
LogicalSize finalSize(wm);
finalSize.BSize(wm) = 0; // BR frames with block size 0 are ignored in quirks
// mode by nsLineLayout::VerticalAlignFrames .
// However, it's not always 0. See below.
finalSize.ISize(wm) = 0;
// Only when the BR is operating in a line-layout situation will it
// behave like a BR. Additionally, we suppress breaks from BR inside
// of ruby frames. To determine if we're inside ruby, we have to rely
// on the *parent's* ShouldSuppressLineBreak() method, instead of our
// own, because we may have custom "display" value that makes our
// ShouldSuppressLineBreak() return false.
nsLineLayout* ll = aReflowInput.mLineLayout;
if (ll && !GetParent()->Style()->ShouldSuppressLineBreak()) {
// Note that the compatibility mode check excludes AlmostStandards
// mode, since this is the inline box model. See bug 161691.
if (ll->LineIsEmpty() ||
aPresContext->CompatibilityMode() == eCompatibility_FullStandards) {
// The line is logically empty; any whitespace is trimmed away.
// If this frame is going to terminate the line we know
// that nothing else will go on the line. Therefore, in this
// case, we provide some height for the BR frame so that it
// creates some vertical whitespace. It's necessary to use the
// line-height rather than the font size because the
// quirks-mode fix that doesn't apply the block's min
// line-height makes this necessary to make BR cause a line
// of the full line-height
// We also do this in strict mode because BR should act like a
// normal inline frame. That line-height is used is important
// here for cases where the line-height is less than 1.
RefPtr<nsFontMetrics> fm =
if (fm) {
nscoord logicalHeight = aReflowInput.GetLineHeight();
finalSize.BSize(wm) = logicalHeight;
fm, logicalHeight, wm.IsLineInverted()));
} else {
aMetrics.SetBlockStartAscent(aMetrics.BSize(wm) = 0);
// XXX temporary until I figure out a better solution; see the
// code in nsLineLayout::VerticalAlignFrames that zaps minY/maxY
// if the width is zero.
// XXX This also fixes bug 10036!
// Warning: nsTextControlFrame::CalculateSizeStandard depends on
// the following line, see bug 228752.
// The code below in AddInlinePrefISize also adds 1 appunit to width
finalSize.ISize(wm) = 1;
// Return our reflow status
aMetrics.SetSize(wm, finalSize);
mAscent = aMetrics.BlockStartAscent();
/* virtual */
void BRFrame::AddInlineMinISize(gfxContext* aRenderingContext,
nsIFrame::InlineMinISizeData* aData) {
if (!GetParent()->Style()->ShouldSuppressLineBreak()) {
/* virtual */
void BRFrame::AddInlinePrefISize(gfxContext* aRenderingContext,
nsIFrame::InlinePrefISizeData* aData) {
if (!GetParent()->Style()->ShouldSuppressLineBreak()) {
// Match the 1 appunit width assigned in the Reflow method above
aData->mCurrentLine += 1;
/* virtual */
nscoord BRFrame::GetMinISize(gfxContext* aRenderingContext) { return 0; }
/* virtual */
nscoord BRFrame::GetPrefISize(gfxContext* aRenderingContext) { return 0; }
Maybe<nscoord> BRFrame::GetNaturalBaselineBOffset(
WritingMode aWM, BaselineSharingGroup aBaselineGroup,
BaselineExportContext) const {
if (aBaselineGroup == BaselineSharingGroup::Last) {
return Nothing{};
return Some(mAscent);
nsIFrame::ContentOffsets BRFrame::CalcContentOffsetsFromFramePoint(
const nsPoint& aPoint) {
ContentOffsets offsets;
offsets.content = mContent->GetParent();
if (offsets.content) {
offsets.offset = offsets.content->ComputeIndexOf_Deprecated(mContent);
offsets.secondaryOffset = offsets.offset;
offsets.associate = CaretAssociationHint::After;
return offsets;
nsIFrame::FrameSearchResult BRFrame::PeekOffsetNoAmount(bool aForward,
int32_t* aOffset) {
NS_ASSERTION(aOffset && *aOffset <= 1, "aOffset out of range");
int32_t startOffset = *aOffset;
// If we hit the end of a BR going backwards, go to its beginning and stay
// there.
if (!aForward && startOffset != 0) {
*aOffset = 0;
return FOUND;
// Otherwise, stop if we hit the beginning, continue (forward) if we hit the
// end.
return (startOffset == 0) ? FOUND : CONTINUE;
nsIFrame::FrameSearchResult BRFrame::PeekOffsetCharacter(
bool aForward, int32_t* aOffset, PeekOffsetCharacterOptions aOptions) {
NS_ASSERTION(aOffset && *aOffset <= 1, "aOffset out of range");
// Keep going. The actual line jumping will stop us.
return CONTINUE;
nsIFrame::FrameSearchResult BRFrame::PeekOffsetWord(
bool aForward, bool aWordSelectEatSpace, bool aIsKeyboardSelect,
int32_t* aOffset, PeekWordState* aState, bool aTrimSpaces) {
NS_ASSERTION(aOffset && *aOffset <= 1, "aOffset out of range");
// Keep going. The actual line jumping will stop us.
return CONTINUE;
a11y::AccType BRFrame::AccessibleType() {
dom::HTMLBRElement* brElement = dom::HTMLBRElement::FromNode(mContent);
if (brElement->IsPaddingForEmptyEditor() ||
brElement->IsPaddingForEmptyLastLine()) {
// This <br> is a "padding <br> element" used when there is no text or an
// empty last line in an editor.
return a11y::eNoType;
return a11y::eHTMLBRType;