dom/svg/DOMSVGPathSegList.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "DOMSVGPathSegList.h"
   8
   9 #include "DOMSVGPathSeg.h"
  10 #include "nsError.h"
  11 #include "SVGAnimatedPathSegList.h"
  12 #include "SVGAttrTearoffTable.h"
  13 #include "SVGPathSegUtils.h"
  14 #include "mozilla/dom/SVGElement.h"
  15 #include "mozilla/dom/SVGPathSegListBinding.h"
  16 #include "mozilla/RefPtr.h"
  17
  18 // See the comment in this file's header.
  19
  20 namespace mozilla {
  21 namespace dom {
  22
  23 static inline SVGAttrTearoffTable<void, DOMSVGPathSegList>&
  24 SVGPathSegListTearoffTable() {
  25   static SVGAttrTearoffTable<void, DOMSVGPathSegList>
  26       sSVGPathSegListTearoffTable;
  27   return sSVGPathSegListTearoffTable;
  28 }
  29
  30 NS_IMPL_CYCLE_COLLECTION_CLASS(DOMSVGPathSegList)
  31
  32 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(DOMSVGPathSegList)
  33   // No unlinking of mElement, we'd need to null out the value pointer (the
  34   // object it points to is held by the element) and null-check it everywhere.
  35   tmp->RemoveFromTearoffTable();
  36   NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
  37 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
  38 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(DOMSVGPathSegList)
  39   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mElement)
  40 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
  41 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(DOMSVGPathSegList)
  42   NS_IMPL_CYCLE_COLLECTION_TRACE_PRESERVED_WRAPPER
  43 NS_IMPL_CYCLE_COLLECTION_TRACE_END
  44
  45 NS_IMPL_CYCLE_COLLECTING_ADDREF(DOMSVGPathSegList)
  46 NS_IMPL_CYCLE_COLLECTING_RELEASE(DOMSVGPathSegList)
  47
  48 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(DOMSVGPathSegList)
  49   NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
  50   NS_INTERFACE_MAP_ENTRY(nsISupports)
  51 NS_INTERFACE_MAP_END
  52
  53 /* static */
  54 already_AddRefed<DOMSVGPathSegList> DOMSVGPathSegList::GetDOMWrapper(
  55     void* aList, SVGElement* aElement, bool aIsAnimValList) {
  56   RefPtr<DOMSVGPathSegList> wrapper =
  57       SVGPathSegListTearoffTable().GetTearoff(aList);
  58   if (!wrapper) {
  59     wrapper = new DOMSVGPathSegList(aElement, aIsAnimValList);
  60     SVGPathSegListTearoffTable().AddTearoff(aList, wrapper);
  61   }
  62   return wrapper.forget();
  63 }
  64
  65 /* static */
  66 DOMSVGPathSegList* DOMSVGPathSegList::GetDOMWrapperIfExists(void* aList) {
  67   return SVGPathSegListTearoffTable().GetTearoff(aList);
  68 }
  69
  70 void DOMSVGPathSegList::RemoveFromTearoffTable() {
  71   // There are now no longer any references to us held by script or list items.
  72   // Note we must use GetAnimValKey/GetBaseValKey here, NOT InternalList()!
  73   void* key = mIsAnimValList ? InternalAList().GetAnimValKey()
  74                              : InternalAList().GetBaseValKey();
  75   SVGPathSegListTearoffTable().RemoveTearoff(key);
  76 }
  77
  78 DOMSVGPathSegList::~DOMSVGPathSegList() { RemoveFromTearoffTable(); }
  79
  80 JSObject* DOMSVGPathSegList::WrapObject(JSContext* cx,
  81                                         JS::Handle<JSObject*> aGivenProto) {
  82   return mozilla::dom::SVGPathSegList_Binding::Wrap(cx, this, aGivenProto);
  83 }
  84
  85 void DOMSVGPathSegList::InternalListWillChangeTo(const SVGPathData& aNewValue) {
  86   // When the number of items in our internal counterpart changes, we MUST stay
  87   // in sync. Everything in the scary comment in
  88   // DOMSVGLengthList::InternalBaseValListWillChangeTo applies here just as
  89   // much, but we have the additional issue that failing to stay in sync would
  90   // mean that - assuming we aren't reading bad memory - we would likely end up
  91   // decoding command types from argument floats when looking in our
  92   // SVGPathData's data array! Either way, we'll likely then go down
  93   // MOZ_ASSERT_UNREACHABLE code paths, or end up reading/setting more bad
  94   // memory!!
  95
  96   // The only time that our other DOM list type implementations remove items is
  97   // if those items become surplus items due to an attribute change or SMIL
  98   // animation sample shortening the list. In general though, they try to keep
  99   // their existing DOM items, even when things change. To be consistent, we'd
 100   // really like to do the same thing. However, because different types of path
 101   // segment correspond to different DOMSVGPathSeg subclasses, the type of
 102   // items in our list are generally not the same, which makes this harder for
 103   // us. We have to remove DOM segments if their type is not the same as the
 104   // type of the new internal segment at their index.
 105   //
 106   // We also need to sync up mInternalDataIndex, but since we need to loop over
 107   // all the items in the new list checking types anyway, that's almost
 108   // insignificant in terms of overhead.
 109   //
 110   // Note that this method is called on every single SMIL animation resample
 111   // and we have no way to short circuit the overhead since we don't have a
 112   // way to tell if the call is due to a new animation, or a resample of an
 113   // existing animation (when the number and type of items would be the same).
 114   // (Note that a new animation could start overriding an existing animation at
 115   // any time, so checking IsAnimating() wouldn't work.) Because we get called
 116   // on every sample, it would not be acceptable alternative to throw away all
 117   // our items and let them be recreated lazily, since that would break what
 118   // script sees!
 119
 120   uint32_t length = mItems.Length();
 121   uint32_t index = 0;
 122
 123   uint32_t dataLength = aNewValue.mData.Length();
 124   uint32_t dataIndex = 0;  // index into aNewValue's raw data array
 125
 126   uint32_t newSegType;
 127
 128   RefPtr<DOMSVGPathSegList> kungFuDeathGrip;
 129   if (length) {
 130     // RemovingFromList() might clear last reference to |this|.
 131     // Retain a temporary reference to keep from dying before returning.
 132     //
 133     // NOTE: For path-seg lists (unlike other list types), we have to do this
 134     // *whenever our list is nonempty* (even if we're growing in length).
 135     // That's because the path-seg-type of any segment could differ between old
 136     // list vs. new list, which will make us destroy & recreate that segment,
 137     // which could remove the last reference to us.
 138     //
 139     // (We explicitly *don't* want to create a kungFuDeathGrip in the length=0
 140     // case, though, because we do hit this code inside our constructor before
 141     // any other owning references have been added, and at that point, the
 142     // deathgrip-removal would make us die before we exit our constructor.)
 143     kungFuDeathGrip = this;
 144   }
 145
 146   while (index < length && dataIndex < dataLength) {
 147     newSegType = SVGPathSegUtils::DecodeType(aNewValue.mData[dataIndex]);
 148     if (ItemAt(index) && ItemAt(index)->Type() != newSegType) {
 149       ItemAt(index)->RemovingFromList();
 150       ItemAt(index) = nullptr;
 151     }
 152     // Only after the RemovingFromList() can we touch mInternalDataIndex!
 153     mItems[index].mInternalDataIndex = dataIndex;
 154     ++index;
 155     dataIndex += 1 + SVGPathSegUtils::ArgCountForType(newSegType);
 156   }
 157
 158   MOZ_ASSERT((index == length && dataIndex <= dataLength) ||
 159                  (index <= length && dataIndex == dataLength),
 160              "very bad - list corruption?");
 161
 162   if (index < length) {
 163     // aNewValue has fewer items than our previous internal counterpart
 164
 165     uint32_t newLength = index;
 166
 167     // Remove excess items from the list:
 168     for (; index < length; ++index) {
 169       if (ItemAt(index)) {
 170         ItemAt(index)->RemovingFromList();
 171         ItemAt(index) = nullptr;
 172       }
 173     }
 174
 175     // Only now may we truncate mItems
 176     mItems.TruncateLength(newLength);
 177   } else if (dataIndex < dataLength) {
 178     // aNewValue has more items than our previous internal counterpart
 179
 180     // Sync mItems:
 181     while (dataIndex < dataLength) {
 182       if (mItems.Length() &&
 183           mItems.Length() - 1 > DOMSVGPathSeg::MaxListIndex()) {
 184         // It's safe to get out of sync with our internal list as long as we
 185         // have FEWER items than it does.
 186         return;
 187       }
 188       if (!mItems.AppendElement(ItemProxy(nullptr, dataIndex), fallible)) {
 189         // OOM
 190         ErrorResult rv;
 191         Clear(rv);
 192         MOZ_ASSERT(!rv.Failed());
 193         return;
 194       }
 195       dataIndex +=
 196           1 + SVGPathSegUtils::ArgCountForType(
 197                   SVGPathSegUtils::DecodeType(aNewValue.mData[dataIndex]));
 198     }
 199   }
 200
 201   MOZ_ASSERT(dataIndex == dataLength, "Serious processing error");
 202   MOZ_ASSERT(index == length, "Serious counting error");
 203 }
 204
 205 bool DOMSVGPathSegList::AttrIsAnimating() const {
 206   return InternalAList().IsAnimating();
 207 }
 208
 209 bool DOMSVGPathSegList::AnimListMirrorsBaseList() const {
 210   return GetDOMWrapperIfExists(InternalAList().GetAnimValKey()) &&
 211          !AttrIsAnimating();
 212 }
 213
 214 SVGPathData& DOMSVGPathSegList::InternalList() const {
 215   SVGAnimatedPathSegList* alist = mElement->GetAnimPathSegList();
 216   return mIsAnimValList && alist->IsAnimating() ? *alist->mAnimVal
 217                                                 : alist->mBaseVal;
 218 }
 219
 220 SVGAnimatedPathSegList& DOMSVGPathSegList::InternalAList() const {
 221   MOZ_ASSERT(mElement->GetAnimPathSegList(), "Internal error");
 222   return *mElement->GetAnimPathSegList();
 223 }
 224
 225 // ----------------------------------------------------------------------------
 226 // nsIDOMSVGPathSegList implementation:
 227
 228 void DOMSVGPathSegList::Clear(ErrorResult& aError) {
 229   if (IsAnimValList()) {
 230     aError.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
 231     return;
 232   }
 233
 234   if (LengthNoFlush() > 0) {
 235     AutoChangePathSegListNotifier notifier(this);
 236     // DOM list items that are to be removed must be removed before we change
 237     // the internal list, otherwise they wouldn't be able to copy their
 238     // internal counterparts' values!
 239
 240     InternalListWillChangeTo(SVGPathData());  // clears mItems
 241
 242     if (!AttrIsAnimating()) {
 243       // The anim val list is in sync with the base val list
 244       DOMSVGPathSegList* animList =
 245           GetDOMWrapperIfExists(InternalAList().GetAnimValKey());
 246       if (animList) {
 247         animList->InternalListWillChangeTo(SVGPathData());  // clears its mItems
 248       }
 249     }
 250
 251     InternalList().Clear();
 252   }
 253 }
 254
 255 already_AddRefed<DOMSVGPathSeg> DOMSVGPathSegList::Initialize(
 256     DOMSVGPathSeg& aNewItem, ErrorResult& aError) {
 257   if (IsAnimValList()) {
 258     aError.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
 259     return nullptr;
 260   }
 261
 262   // If aNewItem is already in a list we should insert a clone of aNewItem,
 263   // and for consistency, this should happen even if *this* is the list that
 264   // aNewItem is currently in. Note that in the case of aNewItem being in this
 265   // list, the Clear() call before the InsertItemBefore() call would remove it
 266   // from this list, and so the InsertItemBefore() call would not insert a
 267   // clone of aNewItem, it would actually insert aNewItem. To prevent that
 268   // from happening we have to do the clone here, if necessary.
 269
 270   RefPtr<DOMSVGPathSeg> domItem = &aNewItem;
 271   if (aNewItem.HasOwner()) {
 272     domItem = aNewItem.Clone();
 273   }
 274
 275   Clear(aError);
 276   MOZ_ASSERT(!aError.Failed(), "How could this fail?");
 277   return InsertItemBefore(*domItem, 0, aError);
 278 }
 279
 280 already_AddRefed<DOMSVGPathSeg> DOMSVGPathSegList::GetItem(uint32_t index,
 281                                                            ErrorResult& error) {
 282   bool found;
 283   RefPtr<DOMSVGPathSeg> item = IndexedGetter(index, found, error);
 284   if (!found) {
 285     error.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
 286   }
 287   return item.forget();
 288 }
 289
 290 already_AddRefed<DOMSVGPathSeg> DOMSVGPathSegList::IndexedGetter(
 291     uint32_t aIndex, bool& aFound, ErrorResult& aError) {
 292   if (IsAnimValList()) {
 293     Element()->FlushAnimations();
 294   }
 295   aFound = aIndex < LengthNoFlush();
 296   if (aFound) {
 297     return GetItemAt(aIndex);
 298   }
 299   return nullptr;
 300 }
 301
 302 already_AddRefed<DOMSVGPathSeg> DOMSVGPathSegList::InsertItemBefore(
 303     DOMSVGPathSeg& aNewItem, uint32_t aIndex, ErrorResult& aError) {
 304   if (IsAnimValList()) {
 305     aError.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
 306     return nullptr;
 307   }
 308
 309   uint32_t internalIndex;
 310   if (aIndex < LengthNoFlush()) {
 311     internalIndex = mItems[aIndex].mInternalDataIndex;
 312   } else {
 313     aIndex = LengthNoFlush();
 314     internalIndex = InternalList().mData.Length();
 315   }
 316   if (aIndex >= DOMSVGPathSeg::MaxListIndex()) {
 317     aError.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
 318     return nullptr;
 319   }
 320
 321   RefPtr<DOMSVGPathSeg> domItem = &aNewItem;
 322   if (domItem->HasOwner()) {
 323     domItem = domItem->Clone();  // must do this before changing anything!
 324   }
 325
 326   uint32_t argCount = SVGPathSegUtils::ArgCountForType(domItem->Type());
 327
 328   // Ensure we have enough memory so we can avoid complex error handling below:
 329   if (!mItems.SetCapacity(mItems.Length() + 1, fallible) ||
 330       !InternalList().mData.SetCapacity(
 331           InternalList().mData.Length() + 1 + argCount, fallible)) {
 332     aError.Throw(NS_ERROR_OUT_OF_MEMORY);
 333     return nullptr;
 334   }
 335   if (AnimListMirrorsBaseList()) {
 336     DOMSVGPathSegList* animVal =
 337         GetDOMWrapperIfExists(InternalAList().GetAnimValKey());
 338     MOZ_ASSERT(animVal, "animVal should be a valid pointer");
 339     if (!animVal->mItems.SetCapacity(animVal->mItems.Length() + 1, fallible)) {
 340       aError.Throw(NS_ERROR_OUT_OF_MEMORY);
 341       return nullptr;
 342     }
 343   }
 344
 345   AutoChangePathSegListNotifier notifier(this);
 346   // Now that we know we're inserting, keep animVal list in sync as necessary.
 347   MaybeInsertNullInAnimValListAt(aIndex, internalIndex, argCount);
 348
 349   float segAsRaw[1 + NS_SVG_PATH_SEG_MAX_ARGS];
 350   domItem->ToSVGPathSegEncodedData(segAsRaw);
 351
 352   MOZ_ALWAYS_TRUE(InternalList().mData.InsertElementsAt(
 353       internalIndex, segAsRaw, 1 + argCount, fallible));
 354   MOZ_ALWAYS_TRUE(mItems.InsertElementAt(
 355       aIndex, ItemProxy(domItem.get(), internalIndex), fallible));
 356
 357   // This MUST come after the insertion into InternalList(), or else under the
 358   // insertion into InternalList() the values read from domItem would be bad
 359   // data from InternalList() itself!:
 360   domItem->InsertingIntoList(this, aIndex, IsAnimValList());
 361
 362   UpdateListIndicesFromIndex(aIndex + 1, argCount + 1);
 363
 364   return domItem.forget();
 365 }
 366
 367 already_AddRefed<DOMSVGPathSeg> DOMSVGPathSegList::ReplaceItem(
 368     DOMSVGPathSeg& aNewItem, uint32_t aIndex, ErrorResult& aError) {
 369   if (IsAnimValList()) {
 370     aError.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
 371     return nullptr;
 372   }
 373
 374   if (aIndex >= LengthNoFlush()) {
 375     aError.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
 376     return nullptr;
 377   }
 378
 379   RefPtr<DOMSVGPathSeg> domItem = &aNewItem;
 380   if (domItem->HasOwner()) {
 381     domItem = domItem->Clone();  // must do this before changing anything!
 382   }
 383
 384   AutoChangePathSegListNotifier notifier(this);
 385   if (ItemAt(aIndex)) {
 386     // Notify any existing DOM item of removal *before* modifying the lists so
 387     // that the DOM item can copy the *old* value at its index:
 388     ItemAt(aIndex)->RemovingFromList();
 389   }
 390
 391   uint32_t internalIndex = mItems[aIndex].mInternalDataIndex;
 392   // We use InternalList() to get oldArgCount since we may not have a DOM
 393   // wrapper at the index being replaced.
 394   uint32_t oldType =
 395       SVGPathSegUtils::DecodeType(InternalList().mData[internalIndex]);
 396
 397   // NOTE: ArgCountForType returns a (small) unsigned value, but we're
 398   // intentionally putting it in a signed variable, because we're going to
 399   // subtract these values and might produce something negative.
 400   int32_t oldArgCount = SVGPathSegUtils::ArgCountForType(oldType);
 401   int32_t newArgCount = SVGPathSegUtils::ArgCountForType(domItem->Type());
 402
 403   float segAsRaw[1 + NS_SVG_PATH_SEG_MAX_ARGS];
 404   domItem->ToSVGPathSegEncodedData(segAsRaw);
 405
 406   if (!InternalList().mData.ReplaceElementsAt(internalIndex, 1 + oldArgCount,
 407                                               segAsRaw, 1 + newArgCount,
 408                                               fallible)) {
 409     aError.Throw(NS_ERROR_OUT_OF_MEMORY);
 410     return nullptr;
 411   }
 412   ItemAt(aIndex) = domItem;
 413
 414   // This MUST come after the ToSVGPathSegEncodedData call, otherwise that call
 415   // would end up reading bad data from InternalList()!
 416   domItem->InsertingIntoList(this, aIndex, IsAnimValList());
 417
 418   int32_t delta = newArgCount - oldArgCount;
 419   if (delta != 0) {
 420     for (uint32_t i = aIndex + 1; i < LengthNoFlush(); ++i) {
 421       mItems[i].mInternalDataIndex += delta;
 422     }
 423   }
 424
 425   return domItem.forget();
 426 }
 427
 428 already_AddRefed<DOMSVGPathSeg> DOMSVGPathSegList::RemoveItem(
 429     uint32_t aIndex, ErrorResult& aError) {
 430   if (IsAnimValList()) {
 431     aError.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
 432     return nullptr;
 433   }
 434
 435   if (aIndex >= LengthNoFlush()) {
 436     aError.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
 437     return nullptr;
 438   }
 439   // We have to return the removed item, so get it, creating it if necessary:
 440   RefPtr<DOMSVGPathSeg> result = GetItemAt(aIndex);
 441
 442   AutoChangePathSegListNotifier notifier(this);
 443   // Notify the DOM item of removal *before* modifying the lists so that the
 444   // DOM item can copy its *old* value:
 445   ItemAt(aIndex)->RemovingFromList();
 446
 447   uint32_t internalIndex = mItems[aIndex].mInternalDataIndex;
 448   uint32_t segType =
 449       SVGPathSegUtils::DecodeType(InternalList().mData[internalIndex]);
 450   // NOTE: ArgCountForType returns a (small) unsigned value, but we're
 451   // intentionally putting it in a signed value, because we're going to
 452   // negate it, and you can't negate an unsigned value.
 453   int32_t argCount = SVGPathSegUtils::ArgCountForType(segType);
 454
 455   // Now that we know we're removing, keep animVal list in sync as necessary.
 456   // Do this *before* touching InternalList() so the removed item can get its
 457   // internal value.
 458   MaybeRemoveItemFromAnimValListAt(aIndex, argCount);
 459
 460   InternalList().mData.RemoveElementsAt(internalIndex, 1 + argCount);
 461   mItems.RemoveElementAt(aIndex);
 462
 463   UpdateListIndicesFromIndex(aIndex, -(argCount + 1));
 464
 465   return result.forget();
 466 }
 467
 468 already_AddRefed<DOMSVGPathSeg> DOMSVGPathSegList::GetItemAt(uint32_t aIndex) {
 469   MOZ_ASSERT(aIndex < mItems.Length());
 470
 471   if (!ItemAt(aIndex)) {
 472     ItemAt(aIndex) = DOMSVGPathSeg::CreateFor(this, aIndex, IsAnimValList());
 473   }
 474   RefPtr<DOMSVGPathSeg> result = ItemAt(aIndex);
 475   return result.forget();
 476 }
 477
 478 void DOMSVGPathSegList::MaybeInsertNullInAnimValListAt(
 479     uint32_t aIndex, uint32_t aInternalIndex, uint32_t aArgCountForItem) {
 480   MOZ_ASSERT(!IsAnimValList(), "call from baseVal to animVal");
 481
 482   if (!AnimListMirrorsBaseList()) {
 483     return;
 484   }
 485
 486   // The anim val list is in sync with the base val list
 487   DOMSVGPathSegList* animVal =
 488       GetDOMWrapperIfExists(InternalAList().GetAnimValKey());
 489
 490   MOZ_ASSERT(animVal, "AnimListMirrorsBaseList() promised a non-null animVal");
 491   MOZ_ASSERT(animVal->mItems.Length() == mItems.Length(),
 492              "animVal list not in sync!");
 493   MOZ_ALWAYS_TRUE(animVal->mItems.InsertElementAt(
 494       aIndex, ItemProxy(nullptr, aInternalIndex), fallible));
 495
 496   animVal->UpdateListIndicesFromIndex(aIndex + 1, 1 + aArgCountForItem);
 497 }
 498
 499 void DOMSVGPathSegList::MaybeRemoveItemFromAnimValListAt(
 500     uint32_t aIndex, int32_t aArgCountForItem) {
 501   MOZ_ASSERT(!IsAnimValList(), "call from baseVal to animVal");
 502
 503   if (!AnimListMirrorsBaseList()) {
 504     return;
 505   }
 506
 507   // This needs to be a strong reference; otherwise, the RemovingFromList call
 508   // below might drop the last reference to animVal before we're done with it.
 509   RefPtr<DOMSVGPathSegList> animVal =
 510       GetDOMWrapperIfExists(InternalAList().GetAnimValKey());
 511
 512   MOZ_ASSERT(animVal, "AnimListMirrorsBaseList() promised a non-null animVal");
 513   MOZ_ASSERT(animVal->mItems.Length() == mItems.Length(),
 514              "animVal list not in sync!");
 515
 516   if (animVal->ItemAt(aIndex)) {
 517     animVal->ItemAt(aIndex)->RemovingFromList();
 518   }
 519   animVal->mItems.RemoveElementAt(aIndex);
 520
 521   animVal->UpdateListIndicesFromIndex(aIndex, -(1 + aArgCountForItem));
 522 }
 523
 524 void DOMSVGPathSegList::UpdateListIndicesFromIndex(
 525     uint32_t aStartingIndex, int32_t aInternalDataIndexDelta) {
 526   uint32_t length = mItems.Length();
 527
 528   for (uint32_t i = aStartingIndex; i < length; ++i) {
 529     mItems[i].mInternalDataIndex += aInternalDataIndexDelta;
 530     if (ItemAt(i)) {
 531       ItemAt(i)->UpdateListIndex(i);
 532     }
 533   }
 534 }
 535
 536 }  // namespace dom
 537 }  // namespace mozilla