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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
#include "mozilla/dom/ResponsiveImageSelector.h"
#include "mozilla/PresShell.h"
#include "mozilla/PresShellInlines.h"
#include "mozilla/ServoStyleSetInlines.h"
#include "mozilla/TextUtils.h"
#include "nsIURI.h"
#include "mozilla/dom/Document.h"
#include "mozilla/dom/DocumentInlines.h"
#include "nsContentUtils.h"
#include "nsPresContext.h"
#include "nsCSSProps.h"
using namespace mozilla;
using namespace mozilla::dom;
namespace mozilla::dom {
NS_IMPL_CYCLE_COLLECTION(ResponsiveImageSelector, mOwnerNode)
static bool ParseInteger(const nsAString& aString, int32_t& aInt) {
nsContentUtils::ParseHTMLIntegerResultFlags parseResult;
aInt = nsContentUtils::ParseHTMLInteger(aString, &parseResult);
return !(parseResult &
(nsContentUtils::eParseHTMLInteger_Error |
nsContentUtils::eParseHTMLInteger_DidNotConsumeAllInput |
nsContentUtils::eParseHTMLInteger_NonStandard));
}
static bool ParseFloat(const nsAString& aString, double& aDouble) {
// Check if it is a valid floating-point number first since the result of
// nsString.ToDouble() is more lenient than the spec,
nsAString::const_iterator iter, end;
aString.BeginReading(iter);
aString.EndReading(end);
if (iter == end) {
return false;
}
if (*iter == char16_t('-') && ++iter == end) {
return false;
}
if (IsAsciiDigit(*iter)) {
for (; iter != end && IsAsciiDigit(*iter); ++iter)
;
} else if (*iter == char16_t('.')) {
// Do nothing, jumps to fraction part
} else {
return false;
}
// Fraction
if (*iter == char16_t('.')) {
++iter;
if (iter == end || !IsAsciiDigit(*iter)) {
// U+002E FULL STOP character (.) must be followed by one or more ASCII
// digits
return false;
}
for (; iter != end && IsAsciiDigit(*iter); ++iter)
;
}
if (iter != end && (*iter == char16_t('e') || *iter == char16_t('E'))) {
++iter;
if (*iter == char16_t('-') || *iter == char16_t('+')) {
++iter;
}
if (iter == end || !IsAsciiDigit(*iter)) {
// Should have one or more ASCII digits
return false;
}
for (; iter != end && IsAsciiDigit(*iter); ++iter)
;
}
if (iter != end) {
return false;
}
nsresult rv;
aDouble = PromiseFlatString(aString).ToDouble(&rv);
return NS_SUCCEEDED(rv);
}
ResponsiveImageSelector::ResponsiveImageSelector(nsIContent* aContent)
: mOwnerNode(aContent), mSelectedCandidateIndex(-1) {}
ResponsiveImageSelector::ResponsiveImageSelector(dom::Document* aDocument)
: mOwnerNode(aDocument), mSelectedCandidateIndex(-1) {}
ResponsiveImageSelector::~ResponsiveImageSelector() = default;
void ResponsiveImageSelector::ParseSourceSet(
const nsAString& aSrcSet,
FunctionRef<void(ResponsiveImageCandidate&&)> aCallback) {
nsAString::const_iterator iter, end;
aSrcSet.BeginReading(iter);
aSrcSet.EndReading(end);
// Read URL / descriptor pairs
while (iter != end) {
nsAString::const_iterator url, urlEnd, descriptor;
// Skip whitespace and commas.
// Extra commas at this point are a non-fatal syntax error.
for (; iter != end &&
(nsContentUtils::IsHTMLWhitespace(*iter) || *iter == char16_t(','));
++iter)
;
if (iter == end) {
break;
}
url = iter;
// Find end of url
for (; iter != end && !nsContentUtils::IsHTMLWhitespace(*iter); ++iter)
;
// Omit trailing commas from URL.
// Multiple commas are a non-fatal error.
while (iter != url) {
if (*(--iter) != char16_t(',')) {
iter++;
break;
}
}
const nsDependentSubstring& urlStr = Substring(url, iter);
MOZ_ASSERT(url != iter, "Shouldn't have empty URL at this point");
ResponsiveImageCandidate candidate;
if (candidate.ConsumeDescriptors(iter, end)) {
candidate.SetURLSpec(urlStr);
aCallback(std::move(candidate));
}
}
}
bool ResponsiveImageSelector::SetCandidatesFromSourceSet(
const nsAString& aSrcSet, nsIPrincipal* aTriggeringPrincipal) {
ClearSelectedCandidate();
if (!mOwnerNode || !mOwnerNode->GetBaseURI()) {
MOZ_ASSERT(false, "Should not be parsing SourceSet without a document");
return false;
}
mCandidates.Clear();
auto eachCandidate = [&](ResponsiveImageCandidate&& aCandidate) {
aCandidate.SetTriggeringPrincipal(
nsContentUtils::GetAttrTriggeringPrincipal(
Content(), aCandidate.URLString(), aTriggeringPrincipal));
AppendCandidateIfUnique(std::move(aCandidate));
};
ParseSourceSet(aSrcSet, eachCandidate);
bool parsedCandidates = !mCandidates.IsEmpty();
// Re-add default to end of list
MaybeAppendDefaultCandidate();
return parsedCandidates;
}
uint32_t ResponsiveImageSelector::NumCandidates(bool aIncludeDefault) {
uint32_t candidates = mCandidates.Length();
// If present, the default candidate is the last item
if (!aIncludeDefault && candidates && mCandidates.LastElement().IsDefault()) {
candidates--;
}
return candidates;
}
nsIContent* ResponsiveImageSelector::Content() {
return mOwnerNode->IsContent() ? mOwnerNode->AsContent() : nullptr;
}
dom::Document* ResponsiveImageSelector::Document() {
return mOwnerNode->OwnerDoc();
}
void ResponsiveImageSelector::ClearDefaultSource() {
ClearSelectedCandidate();
// Check if the last element of our candidates is a default
if (!mCandidates.IsEmpty() && mCandidates.LastElement().IsDefault()) {
mCandidates.RemoveLastElement();
}
}
void ResponsiveImageSelector::SetDefaultSource(nsIURI* aURI,
nsIPrincipal* aPrincipal) {
ClearDefaultSource();
mDefaultSourceTriggeringPrincipal = aPrincipal;
mDefaultSourceURL = VoidString();
if (aURI) {
nsAutoCString spec;
aURI->GetSpec(spec);
CopyUTF8toUTF16(spec, mDefaultSourceURL);
}
MaybeAppendDefaultCandidate();
}
void ResponsiveImageSelector::SetDefaultSource(const nsAString& aURLString,
nsIPrincipal* aPrincipal) {
ClearDefaultSource();
mDefaultSourceTriggeringPrincipal = aPrincipal;
mDefaultSourceURL = aURLString;
MaybeAppendDefaultCandidate();
}
void ResponsiveImageSelector::ClearSelectedCandidate() {
mSelectedCandidateIndex = -1;
mSelectedCandidateURL = nullptr;
}
bool ResponsiveImageSelector::SetSizesFromDescriptor(const nsAString& aSizes) {
ClearSelectedCandidate();
NS_ConvertUTF16toUTF8 sizes(aSizes);
mServoSourceSizeList.reset(Servo_SourceSizeList_Parse(&sizes));
return !!mServoSourceSizeList;
}
void ResponsiveImageSelector::AppendCandidateIfUnique(
ResponsiveImageCandidate&& aCandidate) {
int numCandidates = mCandidates.Length();
// With the exception of Default, which should not be added until we are done
// building the list.
if (aCandidate.IsDefault()) {
return;
}
// Discard candidates with identical parameters, they will never match
for (int i = 0; i < numCandidates; i++) {
if (mCandidates[i].HasSameParameter(aCandidate)) {
return;
}
}
mCandidates.AppendElement(std::move(aCandidate));
}
void ResponsiveImageSelector::MaybeAppendDefaultCandidate() {
if (mDefaultSourceURL.IsEmpty()) {
return;
}
int numCandidates = mCandidates.Length();
// step 4.1.3:
// If child has a src attribute whose value is not the empty string and source
// set does not contain an image source with a density descriptor value of 1,
// and no image source with a width descriptor, append child's src attribute
// value to source set.
for (int i = 0; i < numCandidates; i++) {
if (mCandidates[i].IsComputedFromWidth()) {
return;
} else if (mCandidates[i].Density(this) == 1.0) {
return;
}
}
ResponsiveImageCandidate defaultCandidate;
defaultCandidate.SetParameterDefault();
defaultCandidate.SetURLSpec(mDefaultSourceURL);
defaultCandidate.SetTriggeringPrincipal(mDefaultSourceTriggeringPrincipal);
// We don't use MaybeAppend since we want to keep this even if it can never
// match, as it may if the source set changes.
mCandidates.AppendElement(std::move(defaultCandidate));
}
already_AddRefed<nsIURI> ResponsiveImageSelector::GetSelectedImageURL() {
SelectImage();
nsCOMPtr<nsIURI> url = mSelectedCandidateURL;
return url.forget();
}
bool ResponsiveImageSelector::GetSelectedImageURLSpec(nsAString& aResult) {
SelectImage();
if (mSelectedCandidateIndex == -1) {
return false;
}
aResult.Assign(mCandidates[mSelectedCandidateIndex].URLString());
return true;
}
double ResponsiveImageSelector::GetSelectedImageDensity() {
int bestIndex = GetSelectedCandidateIndex();
if (bestIndex < 0) {
return 1.0;
}
return mCandidates[bestIndex].Density(this);
}
nsIPrincipal* ResponsiveImageSelector::GetSelectedImageTriggeringPrincipal() {
int bestIndex = GetSelectedCandidateIndex();
if (bestIndex < 0) {
return nullptr;
}
return mCandidates[bestIndex].TriggeringPrincipal();
}
bool ResponsiveImageSelector::SelectImage(bool aReselect) {
if (!aReselect && mSelectedCandidateIndex != -1) {
// Already have selection
return false;
}
int oldBest = mSelectedCandidateIndex;
ClearSelectedCandidate();
int numCandidates = mCandidates.Length();
if (!numCandidates) {
return oldBest != -1;
}
dom::Document* doc = Document();
nsPresContext* pctx = doc->GetPresContext();
nsCOMPtr<nsIURI> baseURI = mOwnerNode->GetBaseURI();
if (!pctx || !baseURI) {
return oldBest != -1;
}
double displayDensity = pctx->CSSPixelsToDevPixels(1.0f);
double overrideDPPX = pctx->GetOverrideDPPX();
if (overrideDPPX > 0) {
displayDensity = overrideDPPX;
}
// Per spec, "In a UA-specific manner, choose one image source"
// - For now, select the lowest density greater than displayDensity, otherwise
// the greatest density available
// If the list contains computed width candidates, compute the current
// effective image width.
double computedWidth = -1;
for (int i = 0; i < numCandidates; i++) {
if (mCandidates[i].IsComputedFromWidth()) {
DebugOnly<bool> computeResult =
ComputeFinalWidthForCurrentViewport(&computedWidth);
MOZ_ASSERT(computeResult,
"Computed candidates not allowed without sizes data");
break;
}
}
int bestIndex = -1;
double bestDensity = -1.0;
for (int i = 0; i < numCandidates; i++) {
double candidateDensity = (computedWidth == -1)
? mCandidates[i].Density(this)
: mCandidates[i].Density(computedWidth);
// - If bestIndex is below display density, pick anything larger.
// - Otherwise, prefer if less dense than bestDensity but still above
// displayDensity.
if (bestIndex == -1 ||
(bestDensity < displayDensity && candidateDensity > bestDensity) ||
(candidateDensity >= displayDensity &&
candidateDensity < bestDensity)) {
bestIndex = i;
bestDensity = candidateDensity;
}
}
MOZ_ASSERT(bestIndex >= 0 && bestIndex < numCandidates);
// Resolve URL
nsresult rv;
const nsAString& urlStr = mCandidates[bestIndex].URLString();
nsCOMPtr<nsIURI> candidateURL;
rv = nsContentUtils::NewURIWithDocumentCharset(getter_AddRefs(candidateURL),
urlStr, doc, baseURI);
mSelectedCandidateURL = NS_SUCCEEDED(rv) ? candidateURL : nullptr;
mSelectedCandidateIndex = bestIndex;
return mSelectedCandidateIndex != oldBest;
}
int ResponsiveImageSelector::GetSelectedCandidateIndex() {
SelectImage();
return mSelectedCandidateIndex;
}
bool ResponsiveImageSelector::ComputeFinalWidthForCurrentViewport(
double* aWidth) {
dom::Document* doc = Document();
PresShell* presShell = doc->GetPresShell();
nsPresContext* pctx = presShell ? presShell->GetPresContext() : nullptr;
if (!pctx) {
return false;
}
nscoord effectiveWidth =
presShell->StyleSet()->EvaluateSourceSizeList(mServoSourceSizeList.get());
*aWidth =
nsPresContext::AppUnitsToDoubleCSSPixels(std::max(effectiveWidth, 0));
return true;
}
ResponsiveImageCandidate::ResponsiveImageCandidate() {
mType = CandidateType::Invalid;
mValue.mDensity = 1.0;
}
void ResponsiveImageCandidate::SetURLSpec(const nsAString& aURLString) {
mURLString = aURLString;
}
void ResponsiveImageCandidate::SetTriggeringPrincipal(
nsIPrincipal* aPrincipal) {
mTriggeringPrincipal = aPrincipal;
}
void ResponsiveImageCandidate::SetParameterAsComputedWidth(int32_t aWidth) {
mType = CandidateType::ComputedFromWidth;
mValue.mWidth = aWidth;
}
void ResponsiveImageCandidate::SetParameterDefault() {
MOZ_ASSERT(!IsValid(), "double setting candidate type");
mType = CandidateType::Default;
// mValue shouldn't actually be used for this type, but set it to default
// anyway
mValue.mDensity = 1.0;
}
void ResponsiveImageCandidate::SetParameterInvalid() {
mType = CandidateType::Invalid;
// mValue shouldn't actually be used for this type, but set it to default
// anyway
mValue.mDensity = 1.0;
}
void ResponsiveImageCandidate::SetParameterAsDensity(double aDensity) {
MOZ_ASSERT(!IsValid(), "double setting candidate type");
mType = CandidateType::Density;
mValue.mDensity = aDensity;
}
// Represents all supported descriptors for a ResponsiveImageCandidate, though
// there is no candidate type that uses all of these. This should generally
// match the mValue union of ResponsiveImageCandidate.
struct ResponsiveImageDescriptors {
ResponsiveImageDescriptors() : mInvalid(false){};
Maybe<double> mDensity;
Maybe<int32_t> mWidth;
// We don't support "h" descriptors yet and they are not spec'd, but the
// current spec does specify that they can be silently ignored (whereas
// entirely unknown descriptors cause us to invalidate the candidate)
//
// If we ever start honoring them we should serialize them in
// AppendDescriptors.
Maybe<int32_t> mFutureCompatHeight;
// If this descriptor set is bogus, e.g. a value was added twice (and thus
// dropped) or an unknown descriptor was added.
bool mInvalid;
void AddDescriptor(const nsAString& aDescriptor);
bool Valid();
// Use the current set of descriptors to configure a candidate
void FillCandidate(ResponsiveImageCandidate& aCandidate);
};
// Try to parse a single descriptor from a string. If value already set or
// unknown, sets invalid flag.
// This corresponds to the descriptor "Descriptor parser" step in:
void ResponsiveImageDescriptors::AddDescriptor(const nsAString& aDescriptor) {
if (aDescriptor.IsEmpty()) {
return;
}
// All currently supported descriptors end with an identifying character.
nsAString::const_iterator descStart, descType;
aDescriptor.BeginReading(descStart);
aDescriptor.EndReading(descType);
descType--;
const nsDependentSubstring& valueStr = Substring(descStart, descType);
if (*descType == char16_t('w')) {
int32_t possibleWidth;
// If the value is not a valid non-negative integer, it doesn't match this
// descriptor, fall through.
if (ParseInteger(valueStr, possibleWidth) && possibleWidth >= 0) {
if (possibleWidth != 0 && mWidth.isNothing() && mDensity.isNothing()) {
mWidth.emplace(possibleWidth);
} else {
// Valid width descriptor, but width or density were already seen, sizes
// support isn't enabled, or it parsed to 0, which is an error per spec
mInvalid = true;
}
return;
}
} else if (*descType == char16_t('h')) {
int32_t possibleHeight;
// If the value is not a valid non-negative integer, it doesn't match this
// descriptor, fall through.
if (ParseInteger(valueStr, possibleHeight) && possibleHeight >= 0) {
if (possibleHeight != 0 && mFutureCompatHeight.isNothing() &&
mDensity.isNothing()) {
mFutureCompatHeight.emplace(possibleHeight);
} else {
// Valid height descriptor, but height or density were already seen, or
// it parsed to zero, which is an error per spec
mInvalid = true;
}
return;
}
} else if (*descType == char16_t('x')) {
// If the value is not a valid floating point number, it doesn't match this
// descriptor, fall through.
double possibleDensity = 0.0;
if (ParseFloat(valueStr, possibleDensity)) {
if (possibleDensity >= 0.0 && mWidth.isNothing() &&
mDensity.isNothing() && mFutureCompatHeight.isNothing()) {
mDensity.emplace(possibleDensity);
} else {
// Valid density descriptor, but height or width or density were already
// seen, or it parsed to less than zero, which is an error per spec
mInvalid = true;
}
return;
}
}
// Matched no known descriptor, mark this descriptor set invalid
mInvalid = true;
}
bool ResponsiveImageDescriptors::Valid() {
return !mInvalid && !(mFutureCompatHeight.isSome() && mWidth.isNothing());
}
void ResponsiveImageDescriptors::FillCandidate(
ResponsiveImageCandidate& aCandidate) {
if (!Valid()) {
aCandidate.SetParameterInvalid();
} else if (mWidth.isSome()) {
MOZ_ASSERT(mDensity.isNothing()); // Shouldn't be valid
aCandidate.SetParameterAsComputedWidth(*mWidth);
} else if (mDensity.isSome()) {
MOZ_ASSERT(mWidth.isNothing()); // Shouldn't be valid
aCandidate.SetParameterAsDensity(*mDensity);
} else {
// A valid set of descriptors with no density nor width (e.g. an empty set)
// becomes 1.0 density, per spec
aCandidate.SetParameterAsDensity(1.0);
}
}
bool ResponsiveImageCandidate::ConsumeDescriptors(
nsAString::const_iterator& aIter,
const nsAString::const_iterator& aIterEnd) {
nsAString::const_iterator& iter = aIter;
const nsAString::const_iterator& end = aIterEnd;
bool inParens = false;
ResponsiveImageDescriptors descriptors;
// Parse descriptor list.
// This corresponds to the descriptor parsing loop from:
// Skip initial whitespace
for (; iter != end && nsContentUtils::IsHTMLWhitespace(*iter); ++iter)
;
nsAString::const_iterator currentDescriptor = iter;
for (;; iter++) {
if (iter == end) {
descriptors.AddDescriptor(Substring(currentDescriptor, iter));
break;
} else if (inParens) {
if (*iter == char16_t(')')) {
inParens = false;
}
} else {
if (*iter == char16_t(',')) {
// End of descriptors, flush current descriptor and advance past comma
// before breaking
descriptors.AddDescriptor(Substring(currentDescriptor, iter));
iter++;
break;
}
if (nsContentUtils::IsHTMLWhitespace(*iter)) {
// End of current descriptor, consume it, skip spaces
// ("After descriptor" state in spec) before continuing
descriptors.AddDescriptor(Substring(currentDescriptor, iter));
for (; iter != end && nsContentUtils::IsHTMLWhitespace(*iter); ++iter)
;
if (iter == end) {
break;
}
currentDescriptor = iter;
// Leave one whitespace so the loop advances to this position next
// iteration
iter--;
} else if (*iter == char16_t('(')) {
inParens = true;
}
}
}
descriptors.FillCandidate(*this);
return IsValid();
}
bool ResponsiveImageCandidate::HasSameParameter(
const ResponsiveImageCandidate& aOther) const {
if (aOther.mType != mType) {
return false;
}
if (mType == CandidateType::Default) {
return true;
}
if (mType == CandidateType::Density) {
return aOther.mValue.mDensity == mValue.mDensity;
}
if (mType == CandidateType::Invalid) {
MOZ_ASSERT_UNREACHABLE("Comparing invalid candidates?");
return true;
}
if (mType == CandidateType::ComputedFromWidth) {
return aOther.mValue.mWidth == mValue.mWidth;
}
MOZ_ASSERT(false, "Somebody forgot to check for all uses of this enum");
return false;
}
double ResponsiveImageCandidate::Density(
ResponsiveImageSelector* aSelector) const {
if (mType == CandidateType::ComputedFromWidth) {
double width;
if (!aSelector->ComputeFinalWidthForCurrentViewport(&width)) {
return 1.0;
}
return Density(width);
}
// Other types don't need matching width
MOZ_ASSERT(mType == CandidateType::Default || mType == CandidateType::Density,
"unhandled candidate type");
return Density(-1);
}
void ResponsiveImageCandidate::AppendDescriptors(
nsAString& aDescriptors) const {
MOZ_ASSERT(IsValid());
switch (mType) {
case CandidateType::Default:
case CandidateType::Invalid:
return;
case CandidateType::ComputedFromWidth:
aDescriptors.Append(' ');
aDescriptors.AppendInt(mValue.mWidth);
aDescriptors.Append('w');
return;
case CandidateType::Density:
aDescriptors.Append(' ');
aDescriptors.AppendFloat(mValue.mDensity);
aDescriptors.Append('x');
return;
}
}
double ResponsiveImageCandidate::Density(double aMatchingWidth) const {
if (mType == CandidateType::Invalid) {
MOZ_ASSERT(false, "Getting density for uninitialized candidate");
return 1.0;
}
if (mType == CandidateType::Default) {
return 1.0;
}
if (mType == CandidateType::Density) {
return mValue.mDensity;
}
if (mType == CandidateType::ComputedFromWidth) {
if (aMatchingWidth < 0) {
MOZ_ASSERT(
false,
"Don't expect to have a negative matching width at this point");
return 1.0;
}
double density = double(mValue.mWidth) / aMatchingWidth;
MOZ_ASSERT(density > 0.0);
return density;
}
MOZ_ASSERT(false, "Unknown candidate type");
return 1.0;
}
} // namespace mozilla::dom