Source code

Revision control

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 */
/* the interface (to internal code) for retrieving computed style data */
#include "mozilla/ComputedStyle.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/Maybe.h"
#include "mozilla/ToString.h"
#include "nsCSSAnonBoxes.h"
#include "nsCSSPseudoElements.h"
#include "nsFontMetrics.h"
#include "nsStyleConsts.h"
#include "nsStyleStruct.h"
#include "nsStyleStructInlines.h"
#include "nsString.h"
#include "nsPresContext.h"
#include "nsWindowSizes.h"
#include "nsCOMPtr.h"
#include "GeckoProfiler.h"
#include "mozilla/dom/Document.h"
#include "nsPrintfCString.h"
#include "RubyUtils.h"
#include "mozilla/ComputedStyleInlines.h"
#include "mozilla/Preferences.h"
#include "mozilla/ReflowInput.h"
#include "nsLayoutUtils.h"
#include "nsCoord.h"
// Ensure the binding function declarations in ComputedStyle.h matches
// those in ServoBindings.h.
#include "mozilla/ServoBindings.h"
namespace mozilla {
ComputedStyle::ComputedStyle(PseudoStyleType aPseudoType,
ServoComputedDataForgotten aComputedValues)
: mSource(aComputedValues), mPseudoType(aPseudoType) {}
// If a struct returned nsChangeHint_UpdateContainingBlock, that means that one
// property's influence on whether we're a containing block for abs-pos or
// fixed-pos elements has changed.
// However, we only need to return the hint if the overall computation of
// whether we establish a containing block has really changed.
static bool ContainingBlockMayHaveChanged(const ComputedStyle& aOldStyle,
const ComputedStyle& aNewStyle) {
auto* oldDisp = aOldStyle.StyleDisplay();
auto* newDisp = aNewStyle.StyleDisplay();
if (oldDisp->IsPositionedStyle() != newDisp->IsPositionedStyle()) {
return true;
bool fixedCB =
if (fixedCB !=
newDisp->IsFixedPosContainingBlockForNonSVGTextFrames(aNewStyle)) {
return true;
// If we were both before and after a fixed-pos containing-block that means
// that everything else doesn't matter, since all the other conditions are a
// subset of this.
if (fixedCB) {
return false;
// Note that neither of these two following sets of frames
// (transform-supporting and layout-and-paint-supporting frames) is a subset
// of the other, because table frames support contain: layout/paint but not
// transforms (which are instead inherited to the table wrapper), and quite a
// few frame types support transforms but not contain: layout/paint (e.g.,
// table rows and row groups, many SVG frames).
if (oldDisp->IsFixedPosContainingBlockForTransformSupportingFrames() !=
newDisp->IsFixedPosContainingBlockForTransformSupportingFrames()) {
return true;
if (oldDisp
->IsFixedPosContainingBlockForContainLayoutAndPaintSupportingFrames() !=
->IsFixedPosContainingBlockForContainLayoutAndPaintSupportingFrames()) {
return true;
return false;
nsChangeHint ComputedStyle::CalcStyleDifference(const ComputedStyle& aNewStyle,
uint32_t* aEqualStructs) const {
AUTO_PROFILER_LABEL("ComputedStyle::CalcStyleDifference", LAYOUT);
static_assert(StyleStructConstants::kStyleStructCount <= 32,
"aEqualStructs is not big enough");
*aEqualStructs = 0;
nsChangeHint hint = nsChangeHint(0);
// We must always ensure that we populate the structs on the new style
// context that are filled in on the old context, so that if we get
// two style changes in succession, the second of which causes a real
// style change, the PeekStyleData doesn't return null (implying that
// nobody ever looked at that struct's data). In other words, we
// can't skip later structs if we get a big change up front, because
// we could later get a small change in one of those structs that we
// don't want to miss.
DebugOnly<uint32_t> structsFound = 0;
DebugOnly<int> styleStructCount = 0;
// Servo's optimization to stop the cascade when there are no style changes
// that children need to be recascade for relies on comparing all of the
// structs, not just those that are returned from PeekStyleData, although
// if PeekStyleData does return null we could avoid to accumulate any change
// hints for those structs.
// FIXME(emilio): Reintroduce that optimization either for all kind of structs
// after bug 1368290 with a weak parent pointer from text, or just for reset
// structs.
#define STYLE_STRUCT_BIT(name_) \
#define EXPAND(...) __VA_ARGS__
#define DO_STRUCT_DIFFERENCE_WITH_ARGS(struct_, extra_args_) \
const nsStyle##struct_* this##struct_ = Style##struct_(); \
structsFound |= STYLE_STRUCT_BIT(struct_); \
const nsStyle##struct_* other##struct_ = aNewStyle.Style##struct_(); \
if (this##struct_ == other##struct_) { \
/* The very same struct, so we know that there will be no */ \
/* differences. */ \
*aEqualStructs |= STYLE_STRUCT_BIT(struct_); \
} else { \
nsChangeHint difference = \
this##struct_->CalcDifference(*other##struct_ EXPAND extra_args_); \
hint |= difference; \
if (!difference) { \
*aEqualStructs |= STYLE_STRUCT_BIT(struct_); \
} \
} \
styleStructCount++; \
#define DO_STRUCT_DIFFERENCE(struct_) \
// FIXME: The order of these DO_STRUCT_DIFFERENCE calls is no longer
// significant. With a small amount of effort, we could replace them with a
// #include "nsStyleStructList.h".
DO_STRUCT_DIFFERENCE_WITH_ARGS(Display, (, *StylePosition()));
DO_STRUCT_DIFFERENCE_WITH_ARGS(List, (, *StyleDisplay()));
DO_STRUCT_DIFFERENCE_WITH_ARGS(Position, (, *StyleVisibility()));
#undef EXPAND
MOZ_ASSERT(styleStructCount == StyleStructConstants::kStyleStructCount,
"missing a call to DO_STRUCT_DIFFERENCE");
// Note that we do not check whether this->RelevantLinkVisited() !=
// aNewContext->RelevantLinkVisited(); we don't need to since
// nsCSSFrameConstructor::DoContentStateChanged always adds
// nsChangeHint_RepaintFrame for NS_EVENT_STATE_VISITED changes (and
// needs to, since HasStateDependentStyle probably doesn't work right
// for NS_EVENT_STATE_VISITED). Hopefully this doesn't actually
// expose whether links are visited to performance tests since all
// link coloring happens asynchronously at a time when it's hard for
// the page to measure.
// However, we do need to compute the larger of the changes that can
// happen depending on whether the link is visited or unvisited, since
// doing only the one that's currently appropriate would expose which
// links are in history to easy performance measurement. Therefore,
// here, we add nsChangeHint_RepaintFrame hints (the maximum for
// things that can depend on :visited) for the properties on which we
// call GetVisitedDependentColor.
const ComputedStyle* thisVis = GetStyleIfVisited();
const ComputedStyle* otherVis = aNewStyle.GetStyleIfVisited();
if (!thisVis != !otherVis) {
// One style has a style-if-visited and the other doesn't.
// Presume a difference.
#define STYLE_STRUCT(name_, fields_) *aEqualStructs &= ~STYLE_STRUCT_BIT(name_);
#include "nsCSSVisitedDependentPropList.h"
hint |= nsChangeHint_RepaintFrame;
} else if (thisVis) {
// Both styles have a style-if-visited.
bool change = false;
// NB: Calling Peek on |this|, not |thisVis|, since callers may look
// at a struct on |this| without looking at the same struct on
// |thisVis| (including this function if we skip one of these checks
// due to change being true already or due to the old style not having a
// style-if-visited), but not the other way around.
#define STYLE_FIELD(name_) thisVisStruct->name_ != otherVisStruct->name_
#define STYLE_STRUCT(name_, fields_) \
{ \
const nsStyle##name_* thisVisStruct = thisVis->Style##name_(); \
const nsStyle##name_* otherVisStruct = otherVis->Style##name_(); \
if (MOZ_FOR_EACH_SEPARATED(STYLE_FIELD, (||), (), fields_)) { \
*aEqualStructs &= ~STYLE_STRUCT_BIT(name_); \
change = true; \
} \
#include "nsCSSVisitedDependentPropList.h"
if (change) {
hint |= nsChangeHint_RepaintFrame;
if (hint & nsChangeHint_UpdateContainingBlock) {
if (!ContainingBlockMayHaveChanged(*this, aNewStyle)) {
// While some styles that cause the frame to be a containing block
// has changed, the overall result cannot have changed (no matter
// what the frame type is).
hint &= ~nsChangeHint_UpdateContainingBlock;
if (HasAuthorSpecifiedBorderOrBackground() !=
aNewStyle.HasAuthorSpecifiedBorderOrBackground() &&
StyleDisplay()->HasAppearance()) {
// A background-specified change may cause padding to change, so we may need
// to reflow. We use the same hint here as we do for "appearance" changes.
hint |= nsChangeHint_AllReflowHints | nsChangeHint_RepaintFrame;
MOZ_ASSERT(NS_IsHintSubset(hint, nsChangeHint_AllHints),
"Added a new hint without bumping AllHints?");
return hint & ~nsChangeHint_NeutralChange;
#ifdef DEBUG
void ComputedStyle::List(FILE* out, int32_t aIndent) {
nsAutoCString str;
// Indent
int32_t ix;
for (ix = aIndent; --ix >= 0;) {
str.AppendLiteral(" ");
str.Append(nsPrintfCString("%p(%d) parent=%p ", (void*)this, 0, nullptr));
if (mPseudoType != PseudoStyleType::NotPseudo) {
str.Append(nsPrintfCString("%s ", ToString(mPseudoType).c_str()));
fprintf_stderr(out, "%s{ServoComputedData}\n", str.get());
template <typename Func>
static nscolor GetVisitedDependentColorInternal(const ComputedStyle& aStyle,
Func aColorFunc) {
nscolor colors[2];
colors[0] = aColorFunc(aStyle);
if (const ComputedStyle* visitedStyle = aStyle.GetStyleIfVisited()) {
colors[1] = aColorFunc(*visitedStyle);
return ComputedStyle::CombineVisitedColors(colors,
return colors[0];
static nscolor ExtractColor(const ComputedStyle& aStyle,
const StyleRGBA& aColor) {
return aColor.ToColor();
static nscolor ExtractColor(const ComputedStyle& aStyle,
const StyleColor& aColor) {
return aColor.CalcColor(aStyle);
// Currently caret-color, the only property in the list which is a ColorOrAuto,
// always maps auto to currentcolor.
static nscolor ExtractColor(const ComputedStyle& aStyle,
const StyleColorOrAuto& aColor) {
if (aColor.IsAuto()) {
return ExtractColor(aStyle, StyleColor::CurrentColor());
return ExtractColor(aStyle, aColor.AsColor());
static nscolor ExtractColor(const ComputedStyle& aStyle,
const StyleSVGPaint& aPaintServer) {
return aPaintServer.kind.IsColor()
? ExtractColor(aStyle, aPaintServer.kind.AsColor())
: NS_RGBA(0, 0, 0, 0);
#define STYLE_FIELD(struct_, field_) aField == &struct_::field_ ||
#define STYLE_STRUCT(name_, fields_) \
template <> \
nscolor ComputedStyle::GetVisitedDependentColor(decltype( \
nsStyle##name_::MOZ_ARG_1 fields_) nsStyle##name_::*aField) const { \
MOZ_ASSERT(MOZ_FOR_EACH(STYLE_FIELD, (nsStyle##name_, ), fields_) false, \
"Getting visited-dependent color for a field in nsStyle" #name_ \
" which is not listed in nsCSSVisitedDependentPropList.h"); \
return GetVisitedDependentColorInternal( \
*this, [aField](const ComputedStyle& aStyle) { \
return ExtractColor(aStyle, aStyle.Style##name_()->*aField); \
}); \
#include "nsCSSVisitedDependentPropList.h"
struct ColorIndexSet {
uint8_t colorIndex, alphaIndex;
static const ColorIndexSet gVisitedIndices[2] = {{0, 0}, {1, 0}};
/* static */
nscolor ComputedStyle::CombineVisitedColors(nscolor* aColors,
bool aLinkIsVisited) {
if (NS_GET_A(aColors[1]) == 0) {
// If the style-if-visited is transparent, then just use the
// unvisited style rather than using the (meaningless) color
// components of the visited style along with a potentially
// non-transparent alpha value.
aLinkIsVisited = false;
// NOTE: We want this code to have as little timing dependence as
// possible on whether this->RelevantLinkVisited() is true.
const ColorIndexSet& set = gVisitedIndices[aLinkIsVisited ? 1 : 0];
nscolor colorColor = aColors[set.colorIndex];
nscolor alphaColor = aColors[set.alphaIndex];
return NS_RGBA(NS_GET_R(colorColor), NS_GET_G(colorColor),
NS_GET_B(colorColor), NS_GET_A(alphaColor));
#ifdef DEBUG
/* static */ const char* ComputedStyle::StructName(StyleStructID aSID) {
switch (aSID) {
# define STYLE_STRUCT(name_) \
case StyleStructID::name_: \
return #name_;
# include "nsStyleStructList.h"
return "Unknown";
/* static */
Maybe<StyleStructID> ComputedStyle::LookupStruct(const nsACString& aName) {
# define STYLE_STRUCT(name_) \
if (aName.EqualsLiteral(#name_)) return Some(StyleStructID::name_);
# include "nsStyleStructList.h"
return Nothing();
#endif // DEBUG
ComputedStyle* ComputedStyle::GetCachedLazyPseudoStyle(
PseudoStyleType aPseudo) const {
if (nsCSSPseudoElements::PseudoElementSupportsUserActionState(aPseudo)) {
return nullptr;
return mCachedInheritingStyles.Lookup(aPseudo);
void ComputedStyle::AddSizeOfIncludingThis(nsWindowSizes& aSizes,
size_t* aCVsSize) const {
// Note: |this| sits within a servo_arc::Arc, i.e. it is preceded by a
// refcount. So we need to measure it with a function that can handle an
// interior pointer. We use ServoComputedValuesMallocEnclosingSizeOf to
// clearly identify in DMD's output the memory measured here.
*aCVsSize += ServoComputedValuesMallocEnclosingSizeOf(this);
mCachedInheritingStyles.AddSizeOfIncludingThis(aSizes, aCVsSize);
#ifdef DEBUG
bool ComputedStyle::EqualForCachedAnonymousContentStyle(
const ComputedStyle& aOther) const {
// One thing we can't add UA rules to prevent is different -x-lang
// values being inherited in. So we use this FFI function function rather
// than rely on CalcStyleDifference, which can't tell us which specific
// properties have changed.
return Servo_ComputedValues_EqualForCachedAnonymousContentStyle(this,
} // namespace mozilla