gecko-dev/dom/svg/SVGPathData.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/. */
#ifndef MOZILLA_SVGPATHDATA_H__
#define MOZILLA_SVGPATHDATA_H__
#include "nsCOMPtr.h"
#include "nsDebug.h"
#include "nsIContent.h"
#include "nsINode.h"
#include "nsIWeakReferenceUtils.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/gfx/Types.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/RefPtr.h"
#include "nsSVGElement.h"
#include "nsTArray.h"
#include <string.h>
class nsSVGPathDataParser; // IWYU pragma: keep
struct nsSVGMark;
namespace mozilla {
/**
* ATTENTION! WARNING! WATCH OUT!!
*
* 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 DOMSVGPathSegList;
friend class DOMSVGPathSeg;
friend class ::nsSVGPathDataParser;
// nsSVGPathDataParser will not keep wrappers in sync, so consumers
// are responsible for that!
typedef gfx::DrawTarget DrawTarget;
typedef gfx::Path Path;
typedef gfx::PathBuilder PathBuilder;
typedef gfx::FillRule FillRule;
typedef gfx::Float Float;
typedef gfx::CapStyle CapStyle;
public:
typedef const float* const_iterator;
SVGPathData(){}
~SVGPathData(){}
// 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;
#endif
/**
* 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 float& operator[](uint32_t aIndex) const {
return mData[aIndex];
}
// Used by nsSMILCompositor 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);
}
void Compact() {
mData.Compact();
}
float GetPathLength() const;
uint32_t GetPathSegAtLength(float aLength) const;
void GetMarkerPositioningData(nsTArray<nsSVGMark> *aMarks) const;
/**
* Returns true, except on OOM, in which case returns false.
*/
bool GetSegmentLengths(nsTArray<double> *aLengths) const;
/**
* Returns true, except on OOM, in which case returns false.
*/
bool GetDistancesFromOriginToEndsOfVisibleSegments(FallibleTArray<double> *aArray) const;
/**
* 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.
*/
TemporaryRef<Path> BuildPathForMeasuring() const;
TemporaryRef<Path> BuildPath(PathBuilder* aBuilder,
uint8_t aCapStyle,
Float aStrokeWidth) const;
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.
protected:
typedef float* iterator;
/**
* 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);
}
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 MOZ_FINAL : public SVGPathData
{
public:
explicit SVGPathDataAndInfo(nsSVGElement *aElement = nullptr)
: mElement(do_GetWeakReference(static_cast<nsINode*>(aElement)))
{}
void SetElement(nsSVGElement *aElement) {
mElement = do_GetWeakReference(static_cast<nsINode*>(aElement));
}
nsSVGElement* Element() const {
nsCOMPtr<nsIContent> e = do_QueryReferent(mElement);
return static_cast<nsSVGElement*>(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::SetLength;
using SVGPathData::begin;
using SVGPathData::end;
private:
// We must keep a weak reference to our element because we may belong to a
// cached baseVal nsSMILValue. See the comments starting at:
// https://bugzilla.mozilla.org/show_bug.cgi?id=515116#c15
// See also https://bugzilla.mozilla.org/show_bug.cgi?id=653497
nsWeakPtr mElement;
};
} // namespace mozilla
#endif // MOZILLA_SVGPATHDATA_H__