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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 */
#include "nsPageContentFrame.h"
#include "mozilla/PresShell.h"
#include "mozilla/StaticPrefs_layout.h"
#include "nsContentUtils.h"
#include "nsCSSFrameConstructor.h"
#include "nsPresContext.h"
#include "nsGkAtoms.h"
#include "nsPageSequenceFrame.h"
using namespace mozilla;
nsPageContentFrame* NS_NewPageContentFrame(PresShell* aPresShell,
ComputedStyle* aStyle) {
return new (aPresShell)
nsPageContentFrame(aStyle, aPresShell->GetPresContext());
void nsPageContentFrame::Reflow(nsPresContext* aPresContext,
ReflowOutput& aReflowOutput,
const ReflowInput& aReflowInput,
nsReflowStatus& aStatus) {
DISPLAY_REFLOW(aPresContext, this, aReflowInput, aReflowOutput, aStatus);
MOZ_ASSERT(aStatus.IsEmpty(), "Caller should pass a fresh reflow status!");
MOZ_ASSERT(mPD, "Need a pointer to nsSharedPageData before reflow starts");
if (GetPrevInFlow() && HasAnyStateBits(NS_FRAME_FIRST_REFLOW)) {
nsresult rv =
if (NS_FAILED(rv)) {
// Set our size up front, since some parts of reflow depend on it
// being already set. Note that the computed height may be
// unconstrained; that's ok. Consumers should watch out for that.
nsSize maxSize(aReflowInput.ComputedWidth(), aReflowInput.ComputedHeight());
WritingMode wm = aReflowInput.GetWritingMode();
aReflowOutput.ISize(wm) = aReflowInput.ComputedISize();
if (aReflowInput.ComputedBSize() != NS_UNCONSTRAINEDSIZE) {
aReflowOutput.BSize(wm) = aReflowInput.ComputedBSize();
// A PageContentFrame must always have one child: the canvas frame.
// Resize our frame allowing it only to be as big as we are
// XXX Pay attention to the page's border and padding...
if (mFrames.NotEmpty()) {
nsIFrame* frame = mFrames.FirstChild();
WritingMode wm = frame->GetWritingMode();
LogicalSize logicalSize(wm, maxSize);
ReflowInput kidReflowInput(aPresContext, aReflowInput, frame, logicalSize);
ReflowOutput kidReflowOutput(kidReflowInput);
ReflowChild(frame, aPresContext, kidReflowOutput, kidReflowInput, 0, 0,
ReflowChildFlags::Default, aStatus);
// The document element's background should cover the entire canvas, so
// take into account the combined area and any space taken up by
// absolutely positioned elements
nsMargin padding(0, 0, 0, 0);
// XXXbz this screws up percentage padding (sets padding to zero
// in the percentage padding case)
// This is for shrink-to-fit, and therefore we want to use the
// scrollable overflow, since the purpose of shrink to fit is to
// make the content that ought to be reachable (represented by the
// scrollable overflow) fit in the page.
if (frame->HasOverflowAreas()) {
// The background covers the content area and padding area, so check
// for children sticking outside the child frame's padding edge
nscoord xmost = kidReflowOutput.ScrollableOverflow().XMost();
if (xmost > kidReflowOutput.Width()) {
nscoord widthToFit =
xmost + padding.right +
float ratio = float(maxSize.width) / widthToFit;
NS_ASSERTION(ratio >= 0.0 && ratio < 1.0,
"invalid shrink-to-fit ratio");
mPD->mShrinkToFitRatio = std::min(mPD->mShrinkToFitRatio, ratio);
// In the case of pdf.js documents, we also want to consider the height,
// so that we don't clip the page in either axis if the aspect ratio of
// the PDF doesn't match the destination.
if (nsContentUtils::IsPDFJS(PresContext()->Document()->GetPrincipal())) {
nscoord ymost = kidReflowOutput.ScrollableOverflow().YMost();
if (ymost > kidReflowOutput.Height()) {
nscoord heightToFit =
ymost + padding.bottom +
float ratio = float(maxSize.height) / heightToFit;
MOZ_ASSERT(ratio >= 0.0 && ratio < 1.0);
mPD->mShrinkToFitRatio = std::min(mPD->mShrinkToFitRatio, ratio);
// pdf.js pages should never overflow given the scaling above.
// nsPrintJob::SetupToPrintContent ignores some ratios close to 1.0
// though and doesn't reflow us again in that case, so we need to clear
// the overflow area here in case that happens. (bug 1689789)
kidReflowOutput.mOverflowAreas = aReflowOutput.mOverflowAreas;
// Place and size the child
FinishReflowChild(frame, aPresContext, kidReflowOutput, &kidReflowInput, 0,
0, ReflowChildFlags::Default);
NS_ASSERTION(aPresContext->IsDynamic() || !aStatus.IsFullyComplete() ||
"bad child flow list");
// Reflow our fixed frames
nsReflowStatus fixedStatus;
ReflowAbsoluteFrames(aPresContext, aReflowOutput, aReflowInput, fixedStatus);
"fixed frames can be truncated, but not incomplete");
if (StaticPrefs::layout_display_list_improve_fragmentation() &&
mFrames.NotEmpty()) {
auto* previous = static_cast<nsPageContentFrame*>(GetPrevContinuation());
const nscoord previousPageOverflow =
previous ? previous->mRemainingOverflow : 0;
const nsSize containerSize(aReflowInput.AvailableWidth(),
const nscoord pageBSize = GetLogicalRect(containerSize).BSize(wm);
const nscoord overflowBSize =
LogicalRect(wm, ScrollableOverflowRect(), GetSize()).BEnd(wm);
const nscoord currentPageOverflow = overflowBSize - pageBSize;
nscoord remainingOverflow =
std::max(currentPageOverflow, previousPageOverflow - pageBSize);
if (aStatus.IsFullyComplete() && remainingOverflow > 0) {
// If we have ScrollableOverflow off the end of our page, then we report
// ourselves as overflow-incomplete in order to produce an additional
// content-less page, which we expect to draw our overflow on our behalf.
mRemainingOverflow = std::max(remainingOverflow, 0);
NS_FRAME_SET_TRUNCATION(aStatus, aReflowInput, aReflowOutput);
void nsPageContentFrame::AppendDirectlyOwnedAnonBoxes(
nsTArray<OwnedAnonBox>& aResult) {
"pageContentFrame must have a canvasFrame child");
nsresult nsPageContentFrame::GetFrameName(nsAString& aResult) const {
return MakeFrameName(u"PageContent"_ns, aResult);