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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
#ifndef DOM_SVG_SVGLENGTHLIST_H_
#define DOM_SVG_SVGLENGTHLIST_H_
#include "nsCOMPtr.h"
#include "nsDebug.h"
#include "nsIContent.h"
#include "nsINode.h"
#include "nsIWeakReferenceUtils.h"
#include "SVGElement.h"
#include "nsTArray.h"
#include "SVGLength.h"
#include "mozilla/dom/SVGLengthBinding.h"
namespace mozilla {
namespace dom {
class DOMSVGLength;
class DOMSVGLengthList;
} // namespace dom
/**
* 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 DOMSVGLengthList.
*/
class SVGLengthList {
friend class dom::DOMSVGLength;
friend class dom::DOMSVGLengthList;
friend class SVGAnimatedLengthList;
public:
SVGLengthList() = default;
~SVGLengthList() = default;
SVGLengthList& operator=(const SVGLengthList& aOther) {
mLengths.ClearAndRetainStorage();
// Best-effort, really.
Unused << mLengths.AppendElements(aOther.mLengths, fallible);
return *this;
}
SVGLengthList(const SVGLengthList& aOther) { *this = aOther; }
// 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 mLengths.IsEmpty(); }
uint32_t Length() const { return mLengths.Length(); }
const SVGLength& operator[](uint32_t aIndex) const {
return mLengths[aIndex];
}
bool operator==(const SVGLengthList& rhs) const;
bool SetCapacity(uint32_t size) {
return mLengths.SetCapacity(size, fallible);
}
void Compact() { mLengths.Compact(); }
// 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
// SVGAnimatedLengthList and having that class act as an intermediary so it
// can take care of keeping DOM wrappers in sync.
protected:
/**
* 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 SVGLengthList&);
void SwapWith(SVGLengthList& aOther) {
mLengths.SwapElements(aOther.mLengths);
}
SVGLength& operator[](uint32_t aIndex) { return mLengths[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 aNumberOfItems) {
return mLengths.SetLength(aNumberOfItems, fallible);
}
private:
// Marking the following private only serves to show which methods are only
// used by our friend classes (as opposed to our subclasses) - it doesn't
// really provide additional safety.
nsresult SetValueFromString(const nsAString& aValue);
void Clear() { mLengths.Clear(); }
bool InsertItem(uint32_t aIndex, const SVGLength& aLength) {
if (aIndex >= mLengths.Length()) aIndex = mLengths.Length();
return !!mLengths.InsertElementAt(aIndex, aLength, fallible);
}
void ReplaceItem(uint32_t aIndex, const SVGLength& aLength) {
MOZ_ASSERT(aIndex < mLengths.Length(),
"DOM wrapper caller should have raised INDEX_SIZE_ERR");
mLengths[aIndex] = aLength;
}
void RemoveItem(uint32_t aIndex) {
MOZ_ASSERT(aIndex < mLengths.Length(),
"DOM wrapper caller should have raised INDEX_SIZE_ERR");
mLengths.RemoveElementAt(aIndex);
}
bool AppendItem(SVGLength aLength) {
return !!mLengths.AppendElement(aLength, fallible);
}
protected:
/* Rationale for using nsTArray<SVGLength> and not nsTArray<SVGLength, 1>:
*
* It might seem like we should use AutoTArray<SVGLength, 1> instead of
* nsTArray<SVGLength>. That would preallocate space for one SVGLength and
* avoid an extra memory allocation call in the common case of the 'x'
* and 'y' attributes each containing a single length (and the 'dx' and 'dy'
* attributes being empty). However, consider this:
*
* An empty nsTArray uses sizeof(Header*). An AutoTArray<class E,
* uint32_t N> on the other hand uses sizeof(Header*) +
* (2 * sizeof(uint32_t)) + (N * sizeof(E)), which for one SVGLength is
* sizeof(Header*) + 16 bytes.
*
* Now consider that for text elements we have four length list attributes
* (x, y, dx, dy), each of which can have a baseVal and an animVal list. If
* we were to go the AutoTArray<SVGLength, 1> route for each of these, we'd
* end up using at least 160 bytes for these four attributes alone, even
* though we only need storage for two SVGLengths (16 bytes) in the common
* case!!
*
* A compromise might be to template SVGLengthList to allow
* SVGAnimatedLengthList to preallocate space for an SVGLength for the
* baseVal lists only, and that would cut the space used by the four
* attributes to 96 bytes. Taking that even further and templating
* SVGAnimatedLengthList too in order to only use nsTArray for 'dx' and 'dy'
* would reduce the storage further to 64 bytes. Having different types makes
* things more complicated for code that needs to look at the lists though.
* In fact it also makes things more complicated when it comes to storing the
* lists.
*
* It may be worth considering using nsAttrValue for length lists instead of
* storing them directly on the element.
*/
FallibleTArray<SVGLength> mLengths;
};
/**
* This SVGLengthList subclass is for SVGLengthListSMILType which needs to know
* which element and attribute a length list belongs to so that it can convert
* between unit types if necessary.
*/
class SVGLengthListAndInfo : public SVGLengthList {
public:
SVGLengthListAndInfo() : mElement(nullptr), mAxis(0), mCanZeroPadList(true) {}
SVGLengthListAndInfo(dom::SVGElement* aElement, uint8_t aAxis,
bool aCanZeroPadList)
: mElement(do_GetWeakReference(static_cast<nsINode*>(aElement))),
mAxis(aAxis),
mCanZeroPadList(aCanZeroPadList) {}
void SetInfo(dom::SVGElement* aElement, uint8_t aAxis, bool aCanZeroPadList) {
mElement = do_GetWeakReference(static_cast<nsINode*>(aElement));
mAxis = aAxis;
mCanZeroPadList = aCanZeroPadList;
}
dom::SVGElement* Element() const {
nsCOMPtr<nsIContent> e = do_QueryReferent(mElement);
return static_cast<dom::SVGElement*>(e.get());
}
/**
* 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
* SVGLengthListSMILType::Init() has been changed with a SetInfo() call.
*/
bool IsIdentity() const {
if (!mElement) {
MOZ_ASSERT(IsEmpty(), "target element propagation failure");
return true;
}
return false;
}
uint8_t Axis() const {
MOZ_ASSERT(mElement, "Axis() isn't valid");
return mAxis;
}
/**
* The value returned by this function depends on which attribute this object
* is for. If appending a list of zeros to the attribute's list would have no
* effect on rendering (e.g. the attributes 'dx' and 'dy' on <text>), then
* this method will return true. If appending a list of zeros to the
* attribute's list could *change* rendering (e.g. the attributes 'x' and 'y'
* on <text>), then this method will return false.
*
* The reason that this method exists is because the SMIL code needs to know
* what to do when it's asked to animate between lists of different length.
* If this method returns true, then it can zero pad the short list before
* carrying out its operations. However, in the case of the 'x' and 'y'
* attributes on <text>, zero would mean "zero in the current coordinate
* system", whereas we would want to pad shorter lists with the coordinates
* at which glyphs would otherwise lie, which is almost certainly not zero!
* Animating from/to zeros in this case would produce terrible results.
*
* Currently SVGLengthListSMILType simply disallows (drops) animation between
* lists of different length if it can't zero pad a list. This is to avoid
* having some authors create content that depends on undesirable behaviour
* (which would make it difficult for us to fix the behavior in future). At
* some point it would be nice to implement a callback to allow this code to
* determine padding values for lists that can't be zero padded. See
*/
bool CanZeroPadList() const {
// NS_ASSERTION(mElement, "CanZeroPadList() isn't valid");
return mCanZeroPadList;
}
// For the SMIL code. See comment in SVGLengthListSMILType::Add().
void SetCanZeroPadList(bool aCanZeroPadList) {
mCanZeroPadList = aCanZeroPadList;
}
nsresult CopyFrom(const SVGLengthListAndInfo& rhs) {
mElement = rhs.mElement;
mAxis = rhs.mAxis;
mCanZeroPadList = rhs.mCanZeroPadList;
return SVGLengthList::CopyFrom(rhs);
}
// Instances of this special subclass do not have DOM wrappers that we need
// to worry about keeping in sync, so it's safe to expose any hidden base
// class methods required by the SMIL code, as we do below.
/**
* Exposed so that SVGLengthList baseVals can be copied to
* SVGLengthListAndInfo objects. Note that callers should also call
* SetInfo() when using this method!
*/
nsresult CopyFrom(const SVGLengthList& rhs) {
return SVGLengthList::CopyFrom(rhs);
}
const SVGLength& operator[](uint32_t aIndex) const {
return SVGLengthList::operator[](aIndex);
}
SVGLength& operator[](uint32_t aIndex) {
return SVGLengthList::operator[](aIndex);
}
bool SetLength(uint32_t aNumberOfItems) {
return SVGLengthList::SetLength(aNumberOfItems);
}
private:
// 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;
uint8_t mAxis;
bool mCanZeroPadList;
};
/**
* This class wraps SVGLengthList objects to allow frame consumers to process
* SVGLengthList objects as if they were simply a list of float values in user
* units. When consumers request the value at a given index, this class
* dynamically converts the corresponding SVGLength from its actual unit and
* returns its value in user units.
*
* Consumers should check that the user unit values returned are finite. Even
* if the consumer can guarantee the list's element has a valid viewport
* ancestor to resolve percentage units against, and a valid presContext and
* ComputedStyle to resolve absolute and em/ex units against, unit conversions
* could still overflow. In that case the value returned will be
* numeric_limits<float>::quiet_NaN().
*/
class MOZ_STACK_CLASS SVGUserUnitList {
public:
SVGUserUnitList() : mList(nullptr), mElement(nullptr), mAxis(0) {}
void Init(const SVGLengthList* aList, const dom::SVGElement* aElement,
uint8_t aAxis) {
mList = aList;
mElement = aElement;
mAxis = aAxis;
}
void Clear() { mList = nullptr; }
bool IsEmpty() const { return !mList || mList->IsEmpty(); }
uint32_t Length() const { return mList ? mList->Length() : 0; }
/// This may return a non-finite value
float operator[](uint32_t aIndex) const {
return (*mList)[aIndex].GetValueInPixels(mElement, mAxis);
}
bool HasPercentageValueAt(uint32_t aIndex) const {
const SVGLength& length = (*mList)[aIndex];
return length.GetUnit() ==
dom::SVGLength_Binding::SVG_LENGTHTYPE_PERCENTAGE;
}
private:
const SVGLengthList* mList;
const dom::SVGElement* mElement;
uint8_t mAxis;
};
} // namespace mozilla
#endif // DOM_SVG_SVGLENGTHLIST_H_