gecko-dev/layout/style/nsStyleContext.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 http://mozilla.org/MPL/2.0/. */
/* the interface (to internal code) for retrieving computed style data */
#ifndef _nsStyleContext_h_
#define _nsStyleContext_h_
#include "mozilla/Assertions.h"
#include "mozilla/RestyleLogging.h"
#include "mozilla/ServoStyleSet.h"
#include "mozilla/ServoUtils.h"
#include "mozilla/StyleComplexColor.h"
#include "nsCSSAnonBoxes.h"
#include "nsStyleSet.h"
class nsIAtom;
class nsPresContext;
namespace mozilla {
enum class CSSPseudoElementType : uint8_t;
class GeckoStyleContext;
class ServoStyleContext;
} // namespace mozilla
extern "C" {
void Servo_StyleContext_AddRef(const mozilla::ServoStyleContext* aContext);
void Servo_StyleContext_Release(const mozilla::ServoStyleContext* aContext);
}
/**
* An nsStyleContext represents the computed style data for an element.
* The computed style data are stored in a set of structs (see
* nsStyleStruct.h) that are cached either on the style context or in
* the rule tree (see nsRuleNode.h for a description of this caching and
* how the cached structs are shared).
*
* Since the data in |nsIStyleRule|s and |nsRuleNode|s are immutable
* (with a few exceptions, like system color changes), the data in an
* nsStyleContext are also immutable (with the additional exception of
* GetUniqueStyleData). When style data change,
* ElementRestyler::Restyle creates a new style context.
*
* Style contexts are reference counted. References are generally held
* by:
* 1. the |nsIFrame|s that are using the style context and
* 2. any *child* style contexts (this might be the reverse of
* expectation, but it makes sense in this case)
*/
class nsStyleContext
{
public:
#ifdef MOZ_STYLO
bool IsGecko() const { return !IsServo(); }
bool IsServo() const { return (mBits & NS_STYLE_CONTEXT_IS_GECKO) == 0; }
#else
bool IsGecko() const { return true; }
bool IsServo() const { return false; }
#endif
MOZ_DECL_STYLO_CONVERT_METHODS(mozilla::GeckoStyleContext, mozilla::ServoStyleContext);
// These two methods are for use by ArenaRefPtr.
static mozilla::ArenaObjectID ArenaObjectID()
{
return mozilla::eArenaObjectID_GeckoStyleContext;
}
nsIPresShell* Arena();
inline void AddRef();
inline void Release();
#ifdef DEBUG
void FrameAddRef();
void FrameRelease();
#endif
inline nsPresContext* PresContext() const;
nsIAtom* GetPseudo() const { return mPseudoTag; }
mozilla::CSSPseudoElementType GetPseudoType() const {
return static_cast<mozilla::CSSPseudoElementType>(
mBits >> NS_STYLE_CONTEXT_TYPE_SHIFT);
}
bool IsInheritingAnonBox() const {
return GetPseudoType() == mozilla::CSSPseudoElementType::InheritingAnonBox;
}
bool IsNonInheritingAnonBox() const {
return GetPseudoType() == mozilla::CSSPseudoElementType::NonInheritingAnonBox;
}
// This function is rather slow; you probably don't want to use it outside
// asserts unless you have to. We _could_ add a new CSSPseudoElementType for
// wrapper anon boxes, but that adds a bunch of complexity everywhere we
// resolve anonymous box styles...
bool IsWrapperAnonBox() const {
return nsCSSAnonBoxes::IsWrapperAnonBox(GetPseudo());
}
bool IsAnonBox() const {
return IsInheritingAnonBox() || IsNonInheritingAnonBox();
}
bool IsPseudoElement() const { return mPseudoTag && !IsAnonBox(); }
// Does this style context or any of its ancestors have text
// decoration lines?
// Differs from nsStyleTextReset::HasTextDecorationLines, which tests
// only the data for a single context.
bool HasTextDecorationLines() const
{ return !!(mBits & NS_STYLE_HAS_TEXT_DECORATION_LINES); }
// Whether any line break inside should be suppressed? If this returns
// true, the line should not be broken inside, which means inlines act
// as if nowrap is set, <br> is suppressed, and blocks are inlinized.
// This bit is propogated to all children of line partitipants. It is
// currently used by ruby to make its content frames unbreakable.
// NOTE: for nsTextFrame, use nsTextFrame::ShouldSuppressLineBreak()
// instead of this method.
bool ShouldSuppressLineBreak() const
{ return !!(mBits & NS_STYLE_SUPPRESS_LINEBREAK); }
// Does this style context or any of its ancestors have display:none set?
bool IsInDisplayNoneSubtree() const
{ return !!(mBits & NS_STYLE_IN_DISPLAY_NONE_SUBTREE); }
// Is this horizontal-in-vertical (tate-chu-yoko) text? This flag is
// only set on style contexts whose pseudo is nsCSSAnonBoxes::mozText.
bool IsTextCombined() const
{ return !!(mBits & NS_STYLE_IS_TEXT_COMBINED); }
// Does this style context represent the style for a pseudo-element or
// inherit data from such a style context? Whether this returns true
// is equivalent to whether it or any of its ancestors returns
// non-null for IsPseudoElement().
bool HasPseudoElementData() const
{ return !!(mBits & NS_STYLE_HAS_PSEUDO_ELEMENT_DATA); }
bool HasChildThatUsesResetStyle() const
{ return mBits & NS_STYLE_HAS_CHILD_THAT_USES_RESET_STYLE; }
// Is the only link whose visitedness is allowed to influence the
// style of the node this style context is for (which is that element
// or its nearest ancestor that is a link) visited?
bool RelevantLinkVisited() const
{ return !!(mBits & NS_STYLE_RELEVANT_LINK_VISITED); }
// Is this a style context for a link?
inline bool IsLinkContext() const;
// Is this style context the GetStyleIfVisited() for some other style
// context?
bool IsStyleIfVisited() const
{ return !!(mBits & NS_STYLE_IS_STYLE_IF_VISITED); }
// Tells this style context that it should return true from
// IsStyleIfVisited.
void SetIsStyleIfVisited()
{ mBits |= NS_STYLE_IS_STYLE_IF_VISITED; }
// Return the style context whose style data should be used for the R,
// G, and B components of color, background-color, and border-*-color
// if RelevantLinkIsVisited().
//
// GetPseudo() and GetPseudoType() on this style context return the
// same as on |this|, and its depth in the tree (number of GetParent()
// calls until null is returned) is the same as |this|, since its
// parent is either |this|'s parent or |this|'s parent's
// style-if-visited.
//
// Structs on this context should never be examined without also
// examining the corresponding struct on |this|. Doing so will likely
// both (1) lead to a privacy leak and (2) lead to dynamic change bugs
// related to the Peek code in nsStyleContext::CalcStyleDifference.
inline nsStyleContext* GetStyleIfVisited() const;
// Does any descendant of this style context have any style values
// that were computed based on this style context's ancestors?
bool HasChildThatUsesGrandancestorStyle() const
{ return !!(mBits & NS_STYLE_CHILD_USES_GRANDANCESTOR_STYLE); }
// Is this style context shared with a sibling or cousin?
// (See nsStyleSet::GetContext.)
bool IsShared() const
{ return !!(mBits & NS_STYLE_IS_SHARED); }
/**
* Returns whether this style context has cached style data for a
* given style struct and it does NOT own that struct. This can
* happen because it was inherited from the parent style context, or
* because it was stored conditionally on the rule node.
*/
bool HasCachedDependentStyleData(nsStyleStructID aSID) {
return mBits & nsCachedStyleData::GetBitForSID(aSID);
}
inline nsRuleNode* RuleNode();
inline const ServoComputedData* ComputedData();
void AddStyleBit(const uint64_t& aBit) { mBits |= aBit; }
/**
* Define typesafe getter functions for each style struct by
* preprocessing the list of style structs. These functions are the
* preferred way to get style data. The macro creates functions like:
* const nsStyleBorder* StyleBorder();
* const nsStyleColor* StyleColor();
*/
#define STYLE_STRUCT(name_, checkdata_cb_) \
inline const nsStyle##name_ * Style##name_() MOZ_NONNULL_RETURN;
#include "nsStyleStructList.h"
#undef STYLE_STRUCT
/**
* Equivalent to StyleFoo(), except that we skip the cache write during the
* servo traversal. This can cause incorrect behavior if used improperly,
* since we won't record that layout potentially depends on the values in
* this style struct. Use with care.
*/
#define STYLE_STRUCT(name_, checkdata_cb_) \
inline const nsStyle##name_ * ThreadsafeStyle##name_();
#include "nsStyleStructList.h"
#undef STYLE_STRUCT
/**
* PeekStyle* is like Style* but doesn't trigger style
* computation if the data is not cached on either the style context
* or the rule node.
*
* Perhaps this shouldn't be a public nsStyleContext API.
*/
#define STYLE_STRUCT(name_, checkdata_cb_) \
inline const nsStyle##name_ * PeekStyle##name_();
#include "nsStyleStructList.h"
#undef STYLE_STRUCT
// Value that can be passed as CalcStyleDifference's aRelevantStructs
// argument to indicate that all structs that are currently resolved on the
// old style context should be compared. This is only relevant for
// ServoStyleContexts.
enum { kAllResolvedStructs = 0xffffffff };
static_assert(kAllResolvedStructs != NS_STYLE_INHERIT_MASK,
"uint32_t not big enough for special kAllResolvedStructs value");
/**
* Compute the style changes needed during restyling when this style
* context is being replaced by aNewContext. (This is nonsymmetric since
* we optimize by skipping comparison for styles that have never been
* requested.)
*
* This method returns a change hint (see nsChangeHint.h). All change
* hints apply to the frame and its later continuations or ib-split
* siblings. Most (all of those except the "NotHandledForDescendants"
* hints) also apply to all descendants.
*
* aEqualStructs must not be null. Into it will be stored a bitfield
* representing which structs were compared to be non-equal.
*
* aRelevantStructs must be kAllResolvedStructs for GeckoStyleContexts.
* For ServoStyleContexts, it controls which structs will be compared.
* This is needed because in some cases, we can't rely on mBits in the
* old style context to accurately reflect which are the relevant
* structs to be compared.
*/
nsChangeHint CalcStyleDifference(nsStyleContext* aNewContext,
uint32_t* aEqualStructs,
uint32_t* aSamePointerStructs,
uint32_t aRelevantStructs =
kAllResolvedStructs);
public:
/**
* Get a color that depends on link-visitedness using this and
* this->GetStyleIfVisited().
*
* @param aField A pointer to a member variable in a style struct.
* The member variable and its style struct must have
* been listed in nsCSSVisitedDependentPropList.h.
*/
template<typename T, typename S>
nscolor GetVisitedDependentColor(T S::* aField);
/**
* aColors should be a two element array of nscolor in which the first
* color is the unvisited color and the second is the visited color.
*
* Combine the R, G, and B components of whichever of aColors should
* be used based on aLinkIsVisited with the A component of aColors[0].
*/
static nscolor CombineVisitedColors(nscolor *aColors,
bool aLinkIsVisited);
/**
* Start the background image loads for this style context.
*/
inline void StartBackgroundImageLoads();
#ifdef DEBUG
void List(FILE* out, int32_t aIndent, bool aListDescendants = true);
static const char* StructName(nsStyleStructID aSID);
static bool LookupStruct(const nsACString& aName, nsStyleStructID& aResult);
#endif
protected:
// protected destructor to discourage deletion outside of Release()
~nsStyleContext() {}
// Delegated Helper constructor.
nsStyleContext(nsIAtom* aPseudoTag,
mozilla::CSSPseudoElementType aPseudoType);
// Helper functions for GetStyle* and PeekStyle*
#define STYLE_STRUCT_INHERITED(name_, checkdata_cb_) \
template<bool aComputeData> \
const nsStyle##name_ * DoGetStyle##name_();
#define STYLE_STRUCT_RESET(name_, checkdata_cb_) \
template<bool aComputeData> \
const nsStyle##name_ * DoGetStyle##name_();
#include "nsStyleStructList.h"
#undef STYLE_STRUCT_RESET
#undef STYLE_STRUCT_INHERITED
// If this style context is for a pseudo-element or anonymous box,
// the relevant atom.
RefPtr<nsIAtom> mPseudoTag;
// mBits stores a number of things:
// - It records (using the style struct bits) which structs are
// inherited from the parent context or owned by the rule node (i.e.,
// not owned by the style context).
// - It also stores the additional bits listed at the top of
// nsStyleStruct.h.
uint64_t mBits;
#ifdef DEBUG
static bool DependencyAllowed(nsStyleStructID aOuterSID,
nsStyleStructID aInnerSID)
{
return !!(sDependencyTable[aOuterSID] &
nsCachedStyleData::GetBitForSID(aInnerSID));
}
static const uint32_t sDependencyTable[];
#endif
};
already_AddRefed<mozilla::GeckoStyleContext>
NS_NewStyleContext(mozilla::GeckoStyleContext* aParentContext,
nsIAtom* aPseudoTag,
mozilla::CSSPseudoElementType aPseudoType,
nsRuleNode* aRuleNode,
bool aSkipParentDisplayBasedStyleFixup);
#endif