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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 "nsCOMPtr.h"
#include "nsDebug.h"
#include "nsIContent.h"
#include "nsINode.h"
#include "nsIWeakReferenceUtils.h"
#include "mozilla/dom/SVGElement.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/gfx/Types.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/RefPtr.h"
#include "nsTArray.h"
#include <string.h>
namespace mozilla {
struct StylePathCommand;
struct SVGMark;
enum class StyleStrokeLinecap : uint8_t;
class SVGPathDataParser; // IWYU pragma: keep
namespace dom {
class DOMSVGPathSeg;
class DOMSVGPathSegList;
} // namespace dom
* Consumers that modify objects of this type absolutely MUST keep the DOM
* wrappers for those lists (if any) in sync!! That's why this class is so
* locked down.
* The DOM wrapper class for this class is DOMSVGPathSegList.
* This class is not called |class SVGPathSegList| for one very good reason;
* this class does not provide a list of "SVGPathSeg" items, it provides an
* array of floats into which path segments are encoded. See the paragraphs
* that follow for why. Note that the Length() method returns the number of
* floats in our array, not the number of encoded segments, and the index
* operator indexes floats in the array, not segments. If this class were
* called SVGPathSegList the names of these methods would be very misleading.
* The reason this class is designed in this way is because there are many
* different types of path segment, each taking a different numbers of
* arguments. We want to store the segments in an nsTArray to avoid individual
* allocations for each item, but the different size of segments means we can't
* have one single segment type for the nsTArray (not without using a space
* wasteful union or something similar). Since the internal code does not need
* to index into the list (the DOM wrapper does, but it handles that itself)
* the obvious solution is to have the items in this class take up variable
* width and have the internal code iterate over these lists rather than index
* into them.
* Implementing indexing to segments with O(1) performance would require us to
* allocate and maintain a separate segment index table (keeping that table in
* sync when items are inserted or removed from the list). So long as the
* internal code doesn't require indexing to segments, we can avoid that
* overhead and additional complexity.
* Segment encoding: the first float in the encoding of a segment contains the
* segment's type. The segment's type is encoded to/decoded from this float
* using the static methods SVGPathSegUtils::EncodeType(uint32_t)/
* SVGPathSegUtils::DecodeType(float). If the path segment type in question
* takes any arguments then these follow the first float, and are in the same
* order as they are given in a <path> element's 'd' attribute (NOT in the
* order of the createSVGPathSegXxx() methods' arguments from the SVG DOM
* interface SVGPathElement, which are different...grr). Consumers can use
* SVGPathSegUtils::ArgCountForType(type) to determine how many arguments
* there are (if any), and thus where the current encoded segment ends, and
* where the next segment (if any) begins.
class SVGPathData {
friend class SVGAnimatedPathSegList;
friend class dom::DOMSVGPathSeg;
friend class dom::DOMSVGPathSegList;
friend class SVGPathDataParser;
// SVGPathDataParser will not keep wrappers in sync, so consumers
// are responsible for that!
using DrawTarget = gfx::DrawTarget;
using Path = gfx::Path;
using PathBuilder = gfx::PathBuilder;
using FillRule = gfx::FillRule;
using Float = gfx::Float;
using CapStyle = gfx::CapStyle;
using const_iterator = const float*;
SVGPathData() = default;
~SVGPathData() = default;
// Only methods that don't make/permit modification to this list are public.
// Only our friend classes can access methods that may change us.
/// This may return an incomplete string on OOM, but that's acceptable.
void GetValueAsString(nsAString& aValue) const;
bool IsEmpty() const { return mData.IsEmpty(); }
#ifdef DEBUG
* This method iterates over the encoded segment data and counts the number
* of segments we currently have.
uint32_t CountItems() const;
* Returns the number of *floats* in the encoding array, and NOT the number
* of segments encoded in this object. (For that, see CountItems() above.)
uint32_t Length() const { return mData.Length(); }
const nsTArray<float>& RawData() const { return mData; }
const float& operator[](uint32_t aIndex) const { return mData[aIndex]; }
// Used by SMILCompositor to check if the cached base val is out of date
bool operator==(const SVGPathData& rhs) const {
// We use memcmp so that we don't need to worry that the data encoded in
// the first float may have the same bit pattern as a NaN.
return mData.Length() == rhs.mData.Length() &&
memcmp(mData.Elements(), rhs.mData.Elements(),
mData.Length() * sizeof(float)) == 0;
bool SetCapacity(uint32_t aSize) {
return mData.SetCapacity(aSize, fallible);
void Compact() { mData.Compact(); }
float GetPathLength() const;
uint32_t GetPathSegAtLength(float aDistance) const;
static uint32_t GetPathSegAtLength(Span<const StylePathCommand> aPath,
float aDistance);
void GetMarkerPositioningData(nsTArray<SVGMark>* aMarks) const;
static void GetMarkerPositioningData(Span<const StylePathCommand> aPath,
nsTArray<SVGMark>* aMarks);
* Returns true, except on OOM, in which case returns false.
bool GetDistancesFromOriginToEndsOfVisibleSegments(
FallibleTArray<double>* aOutput) const;
* This is identical to the above one but accepts StylePathCommand.
static bool GetDistancesFromOriginToEndsOfVisibleSegments(
Span<const StylePathCommand> aPath, FallibleTArray<double>* aOutput);
* This returns a path without the extra little line segments that
* ApproximateZeroLengthSubpathSquareCaps can insert if we have square-caps.
* See the comment for that function for more info on that.
already_AddRefed<Path> BuildPathForMeasuring() const;
already_AddRefed<Path> BuildPath(PathBuilder* aBuilder,
StyleStrokeLinecap aStrokeLineCap,
Float aStrokeWidth) const;
static already_AddRefed<Path> BuildPathForMeasuring(
Span<const StylePathCommand> aPath);
* This function tries to build the path from an array of StylePathCommand,
* which is generated by cbindgen from Rust (see ServoStyleConsts.h).
* Basically, this is a variant of the above BuildPath() functions.
static already_AddRefed<Path> BuildPath(Span<const StylePathCommand> aPath,
PathBuilder* aBuilder,
StyleStrokeLinecap aStrokeLineCap,
Float aStrokeWidth,
float aZoomFactor = 1.0);
const_iterator begin() const { return mData.Elements(); }
const_iterator end() const { return mData.Elements() + mData.Length(); }
// memory reporting methods
size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
// Access to methods that can modify objects of this type is deliberately
// limited. This is to reduce the chances of someone modifying objects of
// this type without taking the necessary steps to keep DOM wrappers in sync.
// If you need wider access to these methods, consider adding a method to
// SVGAnimatedPathSegList and having that class act as an intermediary so it
// can take care of keeping DOM wrappers in sync.
using iterator = float*;
* This may fail on OOM if the internal capacity needs to be increased, in
* which case the list will be left unmodified.
nsresult CopyFrom(const SVGPathData& rhs);
float& operator[](uint32_t aIndex) { return mData[aIndex]; }
* This may fail (return false) on OOM if the internal capacity is being
* increased, in which case the list will be left unmodified.
bool SetLength(uint32_t aLength) {
return mData.SetLength(aLength, fallible);
nsresult SetValueFromString(const nsAString& aValue);
void Clear() { mData.Clear(); }
// Our DOM wrappers have direct access to our mData, so they directly
// manipulate it rather than us implementing:
// * InsertItem(uint32_t aDataIndex, uint32_t aType, const float *aArgs);
// * ReplaceItem(uint32_t aDataIndex, uint32_t aType, const float *aArgs);
// * RemoveItem(uint32_t aDataIndex);
// * bool AppendItem(uint32_t aType, const float *aArgs);
nsresult AppendSeg(uint32_t aType, ...); // variable number of float args
iterator begin() { return mData.Elements(); }
iterator end() { return mData.Elements() + mData.Length(); }
FallibleTArray<float> mData;
* This SVGPathData subclass is for SVGPathSegListSMILType which needs to
* have write access to the lists it works with.
* Instances of this class do not have DOM wrappers that need to be kept in
* sync, so we can safely expose any protected base class methods required by
* the SMIL code.
class SVGPathDataAndInfo final : public SVGPathData {
explicit SVGPathDataAndInfo(dom::SVGElement* aElement = nullptr)
: mElement(do_GetWeakReference(static_cast<nsINode*>(aElement))) {}
void SetElement(dom::SVGElement* aElement) {
mElement = do_GetWeakReference(static_cast<nsINode*>(aElement));
dom::SVGElement* Element() const {
nsCOMPtr<nsIContent> e = do_QueryReferent(mElement);
return static_cast<dom::SVGElement*>(e.get());
nsresult CopyFrom(const SVGPathDataAndInfo& rhs) {
mElement = rhs.mElement;
return SVGPathData::CopyFrom(rhs);
* Returns true if this object is an "identity" value, from the perspective
* of SMIL. In other words, returns true until the initial value set up in
* SVGPathSegListSMILType::Init() has been changed with a SetElement() call.
bool IsIdentity() const {
if (!mElement) {
MOZ_ASSERT(IsEmpty(), "target element propagation failure");
return true;
return false;
* Exposed so that SVGPathData baseVals can be copied to
* SVGPathDataAndInfo objects. Note that callers should also call
* SetElement() when using this method!
using SVGPathData::CopyFrom;
// Exposed since SVGPathData objects can be modified.
using SVGPathData::iterator;
using SVGPathData::operator[];
using SVGPathData::begin;
using SVGPathData::end;
using SVGPathData::SetLength;
// We must keep a weak reference to our element because we may belong to a
// cached baseVal SMILValue. See the comments starting at:
nsWeakPtr mElement;
} // namespace mozilla