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336 lines
12 KiB
C++
336 lines
12 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/*
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* compact representation of the property-value pairs within a CSS
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* declaration, and the code for expanding and compacting it
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*/
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#ifndef nsCSSDataBlock_h__
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#define nsCSSDataBlock_h__
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#include "mozilla/MemoryReporting.h"
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#include "nsCSSProps.h"
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#include "nsCSSPropertySet.h"
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struct nsRuleData;
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class nsCSSExpandedDataBlock;
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namespace mozilla {
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namespace css {
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class Declaration;
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}
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}
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/**
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* An |nsCSSCompressedDataBlock| holds a usually-immutable chunk of
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* property-value data for a CSS declaration block (which we misname a
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* |css::Declaration|). Mutation is accomplished through
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* |nsCSSExpandedDataBlock| or in some cases via direct slot access.
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*/
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class nsCSSCompressedDataBlock {
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private:
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friend class nsCSSExpandedDataBlock;
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// Only this class (via |CreateEmptyBlock|) or nsCSSExpandedDataBlock
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// (in |Compress|) can create compressed data blocks.
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nsCSSCompressedDataBlock(uint32_t aNumProps)
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: mStyleBits(0), mNumProps(aNumProps)
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{}
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public:
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~nsCSSCompressedDataBlock();
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/**
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* Do what |nsIStyleRule::MapRuleInfoInto| needs to do for a style
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* rule using this block for storage.
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*/
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void MapRuleInfoInto(nsRuleData *aRuleData) const;
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/**
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* Return the location at which the *value* for the property is
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* stored, or null if the block does not contain a value for the
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* property.
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*
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* Inefficient (by design).
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*
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* Must not be called for shorthands.
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*/
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const nsCSSValue* ValueFor(nsCSSProperty aProperty) const;
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/**
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* Attempt to replace the value for |aProperty| stored in this block
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* with the matching value stored in |aFromBlock|.
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* This method will fail (returning false) if |aProperty| is not
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* already in this block. It will set |aChanged| to true if it
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* actually made a change to the block, but regardless, if it
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* returns true, the value in |aFromBlock| was erased.
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*/
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bool TryReplaceValue(nsCSSProperty aProperty,
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nsCSSExpandedDataBlock& aFromBlock,
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bool* aChanged);
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/**
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* Clone this block, or return null on out-of-memory.
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*/
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nsCSSCompressedDataBlock* Clone() const;
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/**
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* Create a new nsCSSCompressedDataBlock holding no declarations.
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*/
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static nsCSSCompressedDataBlock* CreateEmptyBlock();
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size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
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bool HasDefaultBorderImageSlice() const;
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bool HasDefaultBorderImageWidth() const;
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bool HasDefaultBorderImageOutset() const;
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bool HasDefaultBorderImageRepeat() const;
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private:
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void* operator new(size_t aBaseSize, uint32_t aNumProps) {
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NS_ABORT_IF_FALSE(aBaseSize == sizeof(nsCSSCompressedDataBlock),
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"unexpected size for nsCSSCompressedDataBlock");
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return ::operator new(aBaseSize + DataSize(aNumProps));
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}
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public:
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// Ideally, |nsCSSProperty| would be |enum nsCSSProperty : int16_t|. But
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// not all of the compilers we use are modern enough to support small
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// enums. So we manually squeeze nsCSSProperty into 16 bits ourselves.
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// The static assertion below ensures it fits.
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typedef int16_t CompressedCSSProperty;
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static const size_t MaxCompressedCSSProperty = INT16_MAX;
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private:
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static size_t DataSize(uint32_t aNumProps) {
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return size_t(aNumProps) *
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(sizeof(nsCSSValue) + sizeof(CompressedCSSProperty));
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}
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int32_t mStyleBits; // the structs for which we have data, according to
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// |nsCachedStyleData::GetBitForSID|.
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uint32_t mNumProps;
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// nsCSSValue elements are stored after these fields, and
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// nsCSSProperty elements are stored -- each one compressed as a
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// CompressedCSSProperty -- after the nsCSSValue elements. Space for them
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// is allocated in |operator new| above. The static assertions following
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// this class make sure that the value and property elements are aligned
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// appropriately.
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nsCSSValue* Values() const {
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return (nsCSSValue*)(this + 1);
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}
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CompressedCSSProperty* CompressedProperties() const {
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return (CompressedCSSProperty*)(Values() + mNumProps);
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}
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nsCSSValue* ValueAtIndex(uint32_t i) const {
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NS_ABORT_IF_FALSE(i < mNumProps, "value index out of range");
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return Values() + i;
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}
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nsCSSProperty PropertyAtIndex(uint32_t i) const {
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NS_ABORT_IF_FALSE(i < mNumProps, "property index out of range");
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nsCSSProperty prop = (nsCSSProperty)CompressedProperties()[i];
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NS_ABORT_IF_FALSE(!nsCSSProps::IsShorthand(prop), "out of range");
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return prop;
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}
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void CopyValueToIndex(uint32_t i, nsCSSValue* aValue) {
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new (ValueAtIndex(i)) nsCSSValue(*aValue);
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}
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void RawCopyValueToIndex(uint32_t i, nsCSSValue* aValue) {
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memcpy(ValueAtIndex(i), aValue, sizeof(nsCSSValue));
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}
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void SetPropertyAtIndex(uint32_t i, nsCSSProperty aProperty) {
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NS_ABORT_IF_FALSE(i < mNumProps, "set property index out of range");
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CompressedProperties()[i] = (CompressedCSSProperty)aProperty;
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}
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void SetNumPropsToZero() {
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mNumProps = 0;
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}
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};
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// Make sure the values and properties are aligned appropriately. (These
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// assertions are stronger than necessary to keep them simple.)
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MOZ_STATIC_ASSERT(sizeof(nsCSSCompressedDataBlock) == 8,
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"nsCSSCompressedDataBlock's size has changed");
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MOZ_STATIC_ASSERT(NS_ALIGNMENT_OF(nsCSSValue) == 4 || NS_ALIGNMENT_OF(nsCSSValue) == 8,
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"nsCSSValue doesn't align with nsCSSCompressedDataBlock");
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MOZ_STATIC_ASSERT(NS_ALIGNMENT_OF(nsCSSCompressedDataBlock::CompressedCSSProperty) == 2,
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"CompressedCSSProperty doesn't align with nsCSSValue");
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// Make sure that sizeof(CompressedCSSProperty) is big enough.
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MOZ_STATIC_ASSERT(eCSSProperty_COUNT_no_shorthands <=
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nsCSSCompressedDataBlock::MaxCompressedCSSProperty,
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"nsCSSProperty doesn't fit in StoredSizeOfCSSProperty");
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class nsCSSExpandedDataBlock {
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friend class nsCSSCompressedDataBlock;
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public:
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nsCSSExpandedDataBlock();
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~nsCSSExpandedDataBlock();
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private:
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/* Property storage may not be accessed directly; use AddLonghandProperty
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* and friends.
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*/
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nsCSSValue mValues[eCSSProperty_COUNT_no_shorthands];
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public:
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/**
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* Transfer all of the state from a pair of compressed data blocks
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* to this expanded block. This expanded block must be clear
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* beforehand.
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*
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* This method DELETES both of the compressed data blocks it is
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* passed. (This is necessary because ownership of sub-objects
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* is transferred to the expanded block.)
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*/
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void Expand(nsCSSCompressedDataBlock *aNormalBlock,
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nsCSSCompressedDataBlock *aImportantBlock);
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/**
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* Allocate new compressed blocks and transfer all of the state
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* from this expanded block to the new blocks, clearing this
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* expanded block. A normal block will always be allocated, but
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* an important block will only be allocated if there are
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* !important properties in the expanded block; otherwise
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* |*aImportantBlock| will be set to null.
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*/
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void Compress(nsCSSCompressedDataBlock **aNormalBlock,
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nsCSSCompressedDataBlock **aImportantBlock);
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/**
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* Copy a value into this expanded block. This does NOT destroy
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* the source value object. |aProperty| cannot be a shorthand.
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*/
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void AddLonghandProperty(nsCSSProperty aProperty, const nsCSSValue& aValue);
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/**
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* Clear the state of this expanded block.
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*/
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void Clear();
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/**
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* Clear the data for the given property (including the set and
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* important bits). Can be used with shorthand properties.
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*/
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void ClearProperty(nsCSSProperty aPropID);
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/**
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* Same as ClearProperty, but faster and cannot be used with shorthands.
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*/
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void ClearLonghandProperty(nsCSSProperty aPropID);
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/**
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* Transfer the state for |aPropID| (which may be a shorthand)
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* from |aFromBlock| to this block. The property being transferred
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* is !important if |aIsImportant| is true, and should replace an
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* existing !important property regardless of its own importance
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* if |aOverrideImportant| is true.
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*
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* Returns true if something changed, false otherwise. Calls
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* |ValueAppended| on |aDeclaration| if the property was not
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* previously set, or in any case if |aMustCallValueAppended| is true.
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*/
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bool TransferFromBlock(nsCSSExpandedDataBlock& aFromBlock,
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nsCSSProperty aPropID,
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bool aIsImportant,
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bool aOverrideImportant,
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bool aMustCallValueAppended,
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mozilla::css::Declaration* aDeclaration);
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void AssertInitialState() {
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#ifdef DEBUG
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DoAssertInitialState();
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#endif
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}
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private:
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/**
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* Compute the number of properties that will be present in the
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* result of |Compress|.
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*/
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void ComputeNumProps(uint32_t* aNumPropsNormal,
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uint32_t* aNumPropsImportant);
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void DoExpand(nsCSSCompressedDataBlock *aBlock, bool aImportant);
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/**
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* Worker for TransferFromBlock; cannot be used with shorthands.
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*/
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bool DoTransferFromBlock(nsCSSExpandedDataBlock& aFromBlock,
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nsCSSProperty aPropID,
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bool aIsImportant,
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bool aOverrideImportant,
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bool aMustCallValueAppended,
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mozilla::css::Declaration* aDeclaration);
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#ifdef DEBUG
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void DoAssertInitialState();
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#endif
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/*
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* mPropertiesSet stores a bit for every property that is present,
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* to optimize compression of blocks with small numbers of
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* properties (the norm) and to allow quickly checking whether a
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* property is set in this block.
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*/
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nsCSSPropertySet mPropertiesSet;
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/*
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* mPropertiesImportant indicates which properties are '!important'.
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*/
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nsCSSPropertySet mPropertiesImportant;
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/*
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* Return the storage location within |this| of the value of the
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* property |aProperty|.
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*/
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nsCSSValue* PropertyAt(nsCSSProperty aProperty) {
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NS_ABORT_IF_FALSE(0 <= aProperty &&
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aProperty < eCSSProperty_COUNT_no_shorthands,
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"property out of range");
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return &mValues[aProperty];
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}
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void SetPropertyBit(nsCSSProperty aProperty) {
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mPropertiesSet.AddProperty(aProperty);
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}
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void ClearPropertyBit(nsCSSProperty aProperty) {
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mPropertiesSet.RemoveProperty(aProperty);
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}
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bool HasPropertyBit(nsCSSProperty aProperty) {
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return mPropertiesSet.HasProperty(aProperty);
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}
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void SetImportantBit(nsCSSProperty aProperty) {
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mPropertiesImportant.AddProperty(aProperty);
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}
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void ClearImportantBit(nsCSSProperty aProperty) {
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mPropertiesImportant.RemoveProperty(aProperty);
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}
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bool HasImportantBit(nsCSSProperty aProperty) {
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return mPropertiesImportant.HasProperty(aProperty);
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}
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void ClearSets() {
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mPropertiesSet.Empty();
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mPropertiesImportant.Empty();
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}
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};
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#endif /* !defined(nsCSSDataBlock_h__) */
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