/* -*- 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 http://mozilla.org/MPL/2.0/. */

#ifndef MOZILLA_SVGLENGTHLIST_H__

#define MOZILLA_SVGLENGTHLIST_H__

#include "nsCOMPtr.h"

#include "nsDebug.h"

#include "nsIContent.h"

#include "nsINode.h"

#include "nsIWeakReferenceUtils.h"

#include "nsSVGElement.h"

#include "nsTArray.h"

#include "SVGLength.h"

#include "mozilla/dom/SVGLengthBinding.h"

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 DOMSVGLengthList.

 */

class SVGLengthList

{

  friend class SVGAnimatedLengthList;

  friend class DOMSVGLengthList;

  friend class DOMSVGLength;

public:

  SVGLengthList(){}

  ~SVGLengthList(){}

  // 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& rhs);

  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(false)

  {}

  SVGLengthListAndInfo(nsSVGElement *aElement, uint8_t aAxis, bool aCanZeroPadList)

    : mElement(do_GetWeakReference(static_cast<nsINode*>(aElement)))

    , mAxis(aAxis)

    , mCanZeroPadList(aCanZeroPadList)

  {}

  void SetInfo(nsSVGElement *aElement, uint8_t aAxis, bool aCanZeroPadList) {

    mElement = do_GetWeakReference(static_cast<nsINode*>(aElement));

    mAxis = aAxis;

    mCanZeroPadList = aCanZeroPadList;

  }

  nsSVGElement* Element() const {

    nsCOMPtr<nsIContent> e = do_QueryReferent(mElement);

    return static_cast<nsSVGElement*>(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

   * https://bugzilla.mozilla.org/show_bug.cgi?id=573431

   */

  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 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;

  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, nsSVGElement *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].GetValueInUserUnits(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;

  nsSVGElement *mElement;

  uint8_t mAxis;

};

} // namespace mozilla

#endif // MOZILLA_SVGLENGTHLIST_H__