gecko-dev/dom/svg/DOMSVGPathSegList.cpp

/* -*- 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/. */

#include "nsSVGElement.h"
#include "DOMSVGPathSegList.h"
#include "DOMSVGPathSeg.h"
#include "nsError.h"
#include "SVGAnimatedPathSegList.h"
#include "nsCOMPtr.h"
#include "nsSVGAttrTearoffTable.h"
#include "SVGPathSegUtils.h"
#include "mozilla/dom/SVGPathSegListBinding.h"

// See the comment in this file's header.

namespace mozilla {

  static inline
nsSVGAttrTearoffTable<void, DOMSVGPathSegList>&
SVGPathSegListTearoffTable()
{
  static nsSVGAttrTearoffTable<void, DOMSVGPathSegList>
    sSVGPathSegListTearoffTable;
  return sSVGPathSegListTearoffTable;
}

NS_IMPL_CYCLE_COLLECTION_CLASS(DOMSVGPathSegList)

NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(DOMSVGPathSegList)
  // No unlinking of mElement, we'd need to null out the value pointer (the
  // object it points to is held by the element) and null-check it everywhere.
  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
NS_IMPL_CYCLE_COLLECTION_UNLINK_END
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(DOMSVGPathSegList)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mElement)
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(DOMSVGPathSegList)
  NS_IMPL_CYCLE_COLLECTION_TRACE_PRESERVED_WRAPPER
NS_IMPL_CYCLE_COLLECTION_TRACE_END

NS_IMPL_CYCLE_COLLECTING_ADDREF(DOMSVGPathSegList)
NS_IMPL_CYCLE_COLLECTING_RELEASE(DOMSVGPathSegList)

NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(DOMSVGPathSegList)
  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
  NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END


//----------------------------------------------------------------------
// Helper class: AutoChangePathSegListNotifier
// Stack-based helper class to pair calls to WillChangePathSegList and
// DidChangePathSegList.
class MOZ_RAII AutoChangePathSegListNotifier
{
public:
  explicit AutoChangePathSegListNotifier(DOMSVGPathSegList* aPathSegList MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
    : mPathSegList(aPathSegList)
  {
    MOZ_GUARD_OBJECT_NOTIFIER_INIT;
    MOZ_ASSERT(mPathSegList, "Expecting non-null pathSegList");
    mEmptyOrOldValue =
      mPathSegList->Element()->WillChangePathSegList();
  }

  ~AutoChangePathSegListNotifier()
  {
    mPathSegList->Element()->DidChangePathSegList(mEmptyOrOldValue);
    if (mPathSegList->AttrIsAnimating()) {
      mPathSegList->Element()->AnimationNeedsResample();
    }
  }

private:
  DOMSVGPathSegList* const mPathSegList;
  nsAttrValue        mEmptyOrOldValue;
  MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
};

/* static */ already_AddRefed<DOMSVGPathSegList>
DOMSVGPathSegList::GetDOMWrapper(void *aList,
                                 nsSVGElement *aElement,
                                 bool aIsAnimValList)
{
  RefPtr<DOMSVGPathSegList> wrapper =
    SVGPathSegListTearoffTable().GetTearoff(aList);
  if (!wrapper) {
    wrapper = new DOMSVGPathSegList(aElement, aIsAnimValList);
    SVGPathSegListTearoffTable().AddTearoff(aList, wrapper);
  }
  return wrapper.forget();
}

/* static */ DOMSVGPathSegList*
DOMSVGPathSegList::GetDOMWrapperIfExists(void *aList)
{
  return SVGPathSegListTearoffTable().GetTearoff(aList);
}

DOMSVGPathSegList::~DOMSVGPathSegList()
{
  // There are now no longer any references to us held by script or list items.
  // Note we must use GetAnimValKey/GetBaseValKey here, NOT InternalList()!
  void *key = mIsAnimValList ?
    InternalAList().GetAnimValKey() :
    InternalAList().GetBaseValKey();
  SVGPathSegListTearoffTable().RemoveTearoff(key);
}

JSObject*
DOMSVGPathSegList::WrapObject(JSContext *cx, JS::Handle<JSObject*> aGivenProto)
{
  return mozilla::dom::SVGPathSegList_Binding::Wrap(cx, this, aGivenProto);
}

void
DOMSVGPathSegList::InternalListWillChangeTo(const SVGPathData& aNewValue)
{
  // When the number of items in our internal counterpart changes, we MUST stay
  // in sync. Everything in the scary comment in
  // DOMSVGLengthList::InternalBaseValListWillChangeTo applies here just as
  // much, but we have the additional issue that failing to stay in sync would
  // mean that - assuming we aren't reading bad memory - we would likely end up
  // decoding command types from argument floats when looking in our
  // SVGPathData's data array! Either way, we'll likely then go down
  // MOZ_ASSERT_UNREACHABLE code paths, or end up reading/setting more bad
  // memory!!

  // The only time that our other DOM list type implementations remove items is
  // if those items become surplus items due to an attribute change or SMIL
  // animation sample shortening the list. In general though, they try to keep
  // their existing DOM items, even when things change. To be consistent, we'd
  // really like to do the same thing. However, because different types of path
  // segment correspond to different DOMSVGPathSeg subclasses, the type of
  // items in our list are generally not the same, which makes this harder for
  // us. We have to remove DOM segments if their type is not the same as the
  // type of the new internal segment at their index.
  //
  // We also need to sync up mInternalDataIndex, but since we need to loop over
  // all the items in the new list checking types anyway, that's almost
  // insignificant in terms of overhead.
  //
  // Note that this method is called on every single SMIL animation resample
  // and we have no way to short circuit the overhead since we don't have a
  // way to tell if the call is due to a new animation, or a resample of an
  // existing animation (when the number and type of items would be the same).
  // (Note that a new animation could start overriding an existing animation at
  // any time, so checking IsAnimating() wouldn't work.) Because we get called
  // on every sample, it would not be acceptable alternative to throw away all
  // our items and let them be recreated lazily, since that would break what
  // script sees!

  uint32_t length = mItems.Length();
  uint32_t index = 0;

  uint32_t dataLength = aNewValue.mData.Length();
  uint32_t dataIndex = 0; // index into aNewValue's raw data array

  uint32_t newSegType;

  RefPtr<DOMSVGPathSegList> kungFuDeathGrip;
  if (length) {
    // RemovingFromList() might clear last reference to |this|.
    // Retain a temporary reference to keep from dying before returning.
    //
    // NOTE: For path-seg lists (unlike other list types), we have to do this
    // *whenever our list is nonempty* (even if we're growing in length).
    // That's because the path-seg-type of any segment could differ between old
    // list vs. new list, which will make us destroy & recreate that segment,
    // which could remove the last reference to us.
    //
    // (We explicitly *don't* want to create a kungFuDeathGrip in the length=0
    // case, though, because we do hit this code inside our constructor before
    // any other owning references have been added, and at that point, the
    // deathgrip-removal would make us die before we exit our constructor.)
    kungFuDeathGrip = this;
  }

  while (index < length && dataIndex < dataLength) {
    newSegType = SVGPathSegUtils::DecodeType(aNewValue.mData[dataIndex]);
    if (ItemAt(index) && ItemAt(index)->Type() != newSegType) {
      ItemAt(index)->RemovingFromList();
      ItemAt(index) = nullptr;
    }
    // Only after the RemovingFromList() can we touch mInternalDataIndex!
    mItems[index].mInternalDataIndex = dataIndex;
    ++index;
    dataIndex += 1 + SVGPathSegUtils::ArgCountForType(newSegType);
  }

  MOZ_ASSERT((index == length && dataIndex <= dataLength) ||
             (index <= length && dataIndex == dataLength),
             "very bad - list corruption?");

  if (index < length) {
    // aNewValue has fewer items than our previous internal counterpart

    uint32_t newLength = index;

    // Remove excess items from the list:
    for (; index < length; ++index) {
      if (ItemAt(index)) {
        ItemAt(index)->RemovingFromList();
        ItemAt(index) = nullptr;
      }
    }

    // Only now may we truncate mItems
    mItems.TruncateLength(newLength);
  } else if (dataIndex < dataLength) {
    // aNewValue has more items than our previous internal counterpart

    // Sync mItems:
    while (dataIndex < dataLength) {
      if (mItems.Length() &&
          mItems.Length() - 1 > DOMSVGPathSeg::MaxListIndex()) {
        // It's safe to get out of sync with our internal list as long as we
        // have FEWER items than it does.
        return;
      }
      if (!mItems.AppendElement(ItemProxy(nullptr, dataIndex), fallible)) {
        // OOM
        ErrorResult rv;
        Clear(rv);
        MOZ_ASSERT(!rv.Failed());
        return;
      }
      dataIndex += 1 + SVGPathSegUtils::ArgCountForType(SVGPathSegUtils::DecodeType(aNewValue.mData[dataIndex]));
    }
  }

  MOZ_ASSERT(dataIndex == dataLength, "Serious processing error");
  MOZ_ASSERT(index == length, "Serious counting error");
}

bool
DOMSVGPathSegList::AttrIsAnimating() const
{
  return InternalAList().IsAnimating();
}

bool
DOMSVGPathSegList::AnimListMirrorsBaseList() const
{
  return GetDOMWrapperIfExists(InternalAList().GetAnimValKey()) &&
           !AttrIsAnimating();
}

SVGPathData&
DOMSVGPathSegList::InternalList() const
{
  SVGAnimatedPathSegList *alist = mElement->GetAnimPathSegList();
  return mIsAnimValList && alist->IsAnimating() ? *alist->mAnimVal : alist->mBaseVal;
}

SVGAnimatedPathSegList&
DOMSVGPathSegList::InternalAList() const
{
  MOZ_ASSERT(mElement->GetAnimPathSegList(), "Internal error");
  return *mElement->GetAnimPathSegList();
}

// ----------------------------------------------------------------------------
// nsIDOMSVGPathSegList implementation:

void
DOMSVGPathSegList::Clear(ErrorResult& aError)
{
  if (IsAnimValList()) {
    aError.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
    return;
  }

  if (LengthNoFlush() > 0) {
    AutoChangePathSegListNotifier notifier(this);
    // DOM list items that are to be removed must be removed before we change
    // the internal list, otherwise they wouldn't be able to copy their
    // internal counterparts' values!

    InternalListWillChangeTo(SVGPathData()); // clears mItems

    if (!AttrIsAnimating()) {
      // The anim val list is in sync with the base val list
      DOMSVGPathSegList *animList =
        GetDOMWrapperIfExists(InternalAList().GetAnimValKey());
      if (animList) {
        animList->InternalListWillChangeTo(SVGPathData()); // clears its mItems
      }
    }

    InternalList().Clear();
  }
}

already_AddRefed<DOMSVGPathSeg>
DOMSVGPathSegList::Initialize(DOMSVGPathSeg& aNewItem, ErrorResult& aError)
{
  if (IsAnimValList()) {
    aError.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
    return nullptr;
  }

  // If aNewItem is already in a list we should insert a clone of aNewItem,
  // and for consistency, this should happen even if *this* is the list that
  // aNewItem is currently in. Note that in the case of aNewItem being in this
  // list, the Clear() call before the InsertItemBefore() call would remove it
  // from this list, and so the InsertItemBefore() call would not insert a
  // clone of aNewItem, it would actually insert aNewItem. To prevent that
  // from happening we have to do the clone here, if necessary.

  RefPtr<DOMSVGPathSeg> domItem = &aNewItem;
  if (aNewItem.HasOwner()) {
    domItem = aNewItem.Clone();
  }

  Clear(aError);
  MOZ_ASSERT(!aError.Failed(), "How could this fail?");
  return InsertItemBefore(*domItem, 0, aError);
}

already_AddRefed<DOMSVGPathSeg>
DOMSVGPathSegList::GetItem(uint32_t index, ErrorResult& error)
{
  bool found;
  RefPtr<DOMSVGPathSeg> item = IndexedGetter(index, found, error);
  if (!found) {
    error.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
  }
  return item.forget();
}

already_AddRefed<DOMSVGPathSeg>
DOMSVGPathSegList::IndexedGetter(uint32_t aIndex, bool& aFound,
                                 ErrorResult& aError)
{
  if (IsAnimValList()) {
    Element()->FlushAnimations();
  }
  aFound = aIndex < LengthNoFlush();
  if (aFound) {
    return GetItemAt(aIndex);
  }
  return nullptr;
}

already_AddRefed<DOMSVGPathSeg>
DOMSVGPathSegList::InsertItemBefore(DOMSVGPathSeg& aNewItem,
                                    uint32_t aIndex,
                                    ErrorResult& aError)
{
  if (IsAnimValList()) {
    aError.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
    return nullptr;
  }

  uint32_t internalIndex;
  if (aIndex < LengthNoFlush()) {
    internalIndex = mItems[aIndex].mInternalDataIndex;
  } else {
    aIndex = LengthNoFlush();
    internalIndex = InternalList().mData.Length();
  }
  if (aIndex >= DOMSVGPathSeg::MaxListIndex()) {
    aError.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
    return nullptr;
  }

  RefPtr<DOMSVGPathSeg> domItem = &aNewItem;
  if (domItem->HasOwner()) {
    domItem = domItem->Clone(); // must do this before changing anything!
  }

  uint32_t argCount = SVGPathSegUtils::ArgCountForType(domItem->Type());

  // Ensure we have enough memory so we can avoid complex error handling below:
  if (!mItems.SetCapacity(mItems.Length() + 1, fallible) ||
      !InternalList().mData.SetCapacity(InternalList().mData.Length() + 1 + argCount,
                                        fallible)) {
    aError.Throw(NS_ERROR_OUT_OF_MEMORY);
    return nullptr;
  }
  if (AnimListMirrorsBaseList()) {
    DOMSVGPathSegList *animVal =
      GetDOMWrapperIfExists(InternalAList().GetAnimValKey());
    MOZ_ASSERT(animVal, "animVal should be a valid pointer");
    if (!animVal->mItems.SetCapacity(
          animVal->mItems.Length() + 1, fallible)) {
      aError.Throw(NS_ERROR_OUT_OF_MEMORY);
      return nullptr;
    }
  }

  AutoChangePathSegListNotifier notifier(this);
  // Now that we know we're inserting, keep animVal list in sync as necessary.
  MaybeInsertNullInAnimValListAt(aIndex, internalIndex, argCount);

  float segAsRaw[1 + NS_SVG_PATH_SEG_MAX_ARGS];
  domItem->ToSVGPathSegEncodedData(segAsRaw);

  MOZ_ALWAYS_TRUE(InternalList().mData.InsertElementsAt(internalIndex,
                                                        segAsRaw,
                                                        1 + argCount,
                                                        fallible));
  MOZ_ALWAYS_TRUE(mItems.InsertElementAt(aIndex,
                                         ItemProxy(domItem.get(),
                                                   internalIndex),
                                         fallible));

  // This MUST come after the insertion into InternalList(), or else under the
  // insertion into InternalList() the values read from domItem would be bad
  // data from InternalList() itself!:
  domItem->InsertingIntoList(this, aIndex, IsAnimValList());

  UpdateListIndicesFromIndex(aIndex + 1, argCount + 1);

  return domItem.forget();
}

already_AddRefed<DOMSVGPathSeg>
DOMSVGPathSegList::ReplaceItem(DOMSVGPathSeg& aNewItem,
                               uint32_t aIndex,
                               ErrorResult& aError)
{
  if (IsAnimValList()) {
    aError.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
    return nullptr;
  }

  if (aIndex >= LengthNoFlush()) {
    aError.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
    return nullptr;
  }

  RefPtr<DOMSVGPathSeg> domItem = &aNewItem;
  if (domItem->HasOwner()) {
    domItem = domItem->Clone(); // must do this before changing anything!
  }

  AutoChangePathSegListNotifier notifier(this);
  if (ItemAt(aIndex)) {
    // Notify any existing DOM item of removal *before* modifying the lists so
    // that the DOM item can copy the *old* value at its index:
    ItemAt(aIndex)->RemovingFromList();
  }

  uint32_t internalIndex = mItems[aIndex].mInternalDataIndex;
  // We use InternalList() to get oldArgCount since we may not have a DOM
  // wrapper at the index being replaced.
  uint32_t oldType = SVGPathSegUtils::DecodeType(InternalList().mData[internalIndex]);

  // NOTE: ArgCountForType returns a (small) unsigned value, but we're
  // intentionally putting it in a signed variable, because we're going to
  // subtract these values and might produce something negative.
  int32_t oldArgCount = SVGPathSegUtils::ArgCountForType(oldType);
  int32_t newArgCount = SVGPathSegUtils::ArgCountForType(domItem->Type());

  float segAsRaw[1 + NS_SVG_PATH_SEG_MAX_ARGS];
  domItem->ToSVGPathSegEncodedData(segAsRaw);

  if (!InternalList().mData.ReplaceElementsAt(internalIndex, 1 + oldArgCount,
                                              segAsRaw, 1 + newArgCount,
                                              fallible)) {
    aError.Throw(NS_ERROR_OUT_OF_MEMORY);
    return nullptr;
  }
  ItemAt(aIndex) = domItem;

  // This MUST come after the ToSVGPathSegEncodedData call, otherwise that call
  // would end up reading bad data from InternalList()!
  domItem->InsertingIntoList(this, aIndex, IsAnimValList());

  int32_t delta = newArgCount - oldArgCount;
  if (delta != 0) {
    for (uint32_t i = aIndex + 1; i < LengthNoFlush(); ++i) {
      mItems[i].mInternalDataIndex += delta;
    }
  }

  return domItem.forget();
}

already_AddRefed<DOMSVGPathSeg>
DOMSVGPathSegList::RemoveItem(uint32_t aIndex,
                              ErrorResult& aError)
{
  if (IsAnimValList()) {
    aError.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
    return nullptr;
  }

  if (aIndex >= LengthNoFlush()) {
    aError.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
    return nullptr;
  }
  // We have to return the removed item, so get it, creating it if necessary:
  RefPtr<DOMSVGPathSeg> result = GetItemAt(aIndex);

  AutoChangePathSegListNotifier notifier(this);
  // Notify the DOM item of removal *before* modifying the lists so that the
  // DOM item can copy its *old* value:
  ItemAt(aIndex)->RemovingFromList();

  uint32_t internalIndex = mItems[aIndex].mInternalDataIndex;
  uint32_t segType = SVGPathSegUtils::DecodeType(InternalList().mData[internalIndex]);
  // NOTE: ArgCountForType returns a (small) unsigned value, but we're
  // intentionally putting it in a signed value, because we're going to
  // negate it, and you can't negate an unsigned value.
  int32_t argCount = SVGPathSegUtils::ArgCountForType(segType);

  // Now that we know we're removing, keep animVal list in sync as necessary.
  // Do this *before* touching InternalList() so the removed item can get its
  // internal value.
  MaybeRemoveItemFromAnimValListAt(aIndex, argCount);

  InternalList().mData.RemoveElementsAt(internalIndex, 1 + argCount);
  mItems.RemoveElementAt(aIndex);

  UpdateListIndicesFromIndex(aIndex, -(argCount + 1));

  return result.forget();
}

already_AddRefed<DOMSVGPathSeg>
DOMSVGPathSegList::GetItemAt(uint32_t aIndex)
{
  MOZ_ASSERT(aIndex < mItems.Length());

  if (!ItemAt(aIndex)) {
    ItemAt(aIndex) = DOMSVGPathSeg::CreateFor(this, aIndex, IsAnimValList());
  }
  RefPtr<DOMSVGPathSeg> result = ItemAt(aIndex);
  return result.forget();
}

void
DOMSVGPathSegList::
  MaybeInsertNullInAnimValListAt(uint32_t aIndex,
                                 uint32_t aInternalIndex,
                                 uint32_t aArgCountForItem)
{
  MOZ_ASSERT(!IsAnimValList(), "call from baseVal to animVal");

  if (!AnimListMirrorsBaseList()) {
    return;
  }

  // The anim val list is in sync with the base val list
  DOMSVGPathSegList *animVal =
    GetDOMWrapperIfExists(InternalAList().GetAnimValKey());

  MOZ_ASSERT(animVal, "AnimListMirrorsBaseList() promised a non-null animVal");
  MOZ_ASSERT(animVal->mItems.Length() == mItems.Length(),
             "animVal list not in sync!");
  MOZ_ALWAYS_TRUE(animVal->mItems.InsertElementAt(aIndex,
                                                  ItemProxy(nullptr,
                                                            aInternalIndex),
                                                  fallible));

  animVal->UpdateListIndicesFromIndex(aIndex + 1, 1 + aArgCountForItem);
}

void
DOMSVGPathSegList::
  MaybeRemoveItemFromAnimValListAt(uint32_t aIndex,
                                   int32_t aArgCountForItem)
{
  MOZ_ASSERT(!IsAnimValList(), "call from baseVal to animVal");

  if (!AnimListMirrorsBaseList()) {
    return;
  }

  // This needs to be a strong reference; otherwise, the RemovingFromList call
  // below might drop the last reference to animVal before we're done with it.
  RefPtr<DOMSVGPathSegList> animVal =
    GetDOMWrapperIfExists(InternalAList().GetAnimValKey());

  MOZ_ASSERT(animVal, "AnimListMirrorsBaseList() promised a non-null animVal");
  MOZ_ASSERT(animVal->mItems.Length() == mItems.Length(),
             "animVal list not in sync!");

  if (animVal->ItemAt(aIndex)) {
    animVal->ItemAt(aIndex)->RemovingFromList();
  }
  animVal->mItems.RemoveElementAt(aIndex);

  animVal->UpdateListIndicesFromIndex(aIndex, -(1 + aArgCountForItem));
}

void
DOMSVGPathSegList::UpdateListIndicesFromIndex(uint32_t aStartingIndex,
                                              int32_t  aInternalDataIndexDelta)
{
  uint32_t length = mItems.Length();

  for (uint32_t i = aStartingIndex; i < length; ++i) {
    mItems[i].mInternalDataIndex += aInternalDataIndexDelta;
    if (ItemAt(i)) {
      ItemAt(i)->UpdateListIndex(i);
    }
  }
}

} // namespace mozilla