dom/smil/SMILCSSValueType.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 /* representation of a value for a SMIL-animated CSS property */
   8
   9 #include "SMILCSSValueType.h"
  10
  11 #include "nsComputedDOMStyle.h"
  12 #include "nsColor.h"
  13 #include "nsCSSProps.h"
  14 #include "nsCSSValue.h"
  15 #include "nsDebug.h"
  16 #include "nsPresContextInlines.h"
  17 #include "nsPresContext.h"
  18 #include "nsString.h"
  19 #include "nsStyleUtil.h"
  20 #include "mozilla/DeclarationBlock.h"
  21 #include "mozilla/PresShell.h"
  22 #include "mozilla/PresShellInlines.h"
  23 #include "mozilla/ServoBindings.h"
  24 #include "mozilla/StyleAnimationValue.h"
  25 #include "mozilla/ServoCSSParser.h"
  26 #include "mozilla/ServoStyleSet.h"
  27 #include "mozilla/SMILParserUtils.h"
  28 #include "mozilla/SMILValue.h"
  29 #include "mozilla/dom/BaseKeyframeTypesBinding.h"
  30 #include "mozilla/dom/Document.h"
  31 #include "mozilla/dom/Element.h"
  32
  33 using namespace mozilla::dom;
  34
  35 namespace mozilla {
  36
  37 using ServoAnimationValues = CopyableAutoTArray<RefPtr<StyleAnimationValue>, 1>;
  38
  39 /*static*/
  40 SMILCSSValueType SMILCSSValueType::sSingleton;
  41
  42 struct ValueWrapper {
  43   ValueWrapper(nsCSSPropertyID aPropID, const AnimationValue& aValue)
  44       : mPropID(aPropID) {
  45     MOZ_ASSERT(!aValue.IsNull());
  46     mServoValues.AppendElement(aValue.mServo);
  47   }
  48   ValueWrapper(nsCSSPropertyID aPropID,
  49                const RefPtr<StyleAnimationValue>& aValue)
  50       : mPropID(aPropID), mServoValues{(aValue)} {}
  51   ValueWrapper(nsCSSPropertyID aPropID, ServoAnimationValues&& aValues)
  52       : mPropID(aPropID), mServoValues{std::move(aValues)} {}
  53
  54   bool operator==(const ValueWrapper& aOther) const {
  55     if (mPropID != aOther.mPropID) {
  56       return false;
  57     }
  58
  59     MOZ_ASSERT(!mServoValues.IsEmpty());
  60     size_t len = mServoValues.Length();
  61     if (len != aOther.mServoValues.Length()) {
  62       return false;
  63     }
  64     for (size_t i = 0; i < len; i++) {
  65       if (!Servo_AnimationValue_DeepEqual(mServoValues[i],
  66                                           aOther.mServoValues[i])) {
  67         return false;
  68       }
  69     }
  70     return true;
  71   }
  72
  73   bool operator!=(const ValueWrapper& aOther) const {
  74     return !(*this == aOther);
  75   }
  76
  77   nsCSSPropertyID mPropID;
  78   ServoAnimationValues mServoValues;
  79 };
  80
  81 // Helper Methods
  82 // --------------
  83
  84 // If one argument is null, this method updates it to point to "zero"
  85 // for the other argument's Unit (if applicable; otherwise, we return false).
  86 //
  87 // If neither argument is null, this method simply returns true.
  88 //
  89 // If both arguments are null, this method returns false.
  90 //
  91 // |aZeroValueStorage| should be a reference to a
  92 // RefPtr<StyleAnimationValue>. This is used where we may need to allocate a
  93 // new ServoAnimationValue to represent the appropriate zero value.
  94 //
  95 // Returns true on success, or otherwise.
  96 static bool FinalizeServoAnimationValues(
  97     const RefPtr<StyleAnimationValue>*& aValue1,
  98     const RefPtr<StyleAnimationValue>*& aValue2,
  99     RefPtr<StyleAnimationValue>& aZeroValueStorage) {
 100   if (!aValue1 && !aValue2) {
 101     return false;
 102   }
 103
 104   // Are we missing either val? (If so, it's an implied 0 in other val's units)
 105
 106   if (!aValue1) {
 107     aZeroValueStorage = Servo_AnimationValues_GetZeroValue(*aValue2).Consume();
 108     aValue1 = &aZeroValueStorage;
 109   } else if (!aValue2) {
 110     aZeroValueStorage = Servo_AnimationValues_GetZeroValue(*aValue1).Consume();
 111     aValue2 = &aZeroValueStorage;
 112   }
 113   return *aValue1 && *aValue2;
 114 }
 115
 116 static ValueWrapper* ExtractValueWrapper(SMILValue& aValue) {
 117   return static_cast<ValueWrapper*>(aValue.mU.mPtr);
 118 }
 119
 120 static const ValueWrapper* ExtractValueWrapper(const SMILValue& aValue) {
 121   return static_cast<const ValueWrapper*>(aValue.mU.mPtr);
 122 }
 123
 124 // Class methods
 125 // -------------
 126 void SMILCSSValueType::Init(SMILValue& aValue) const {
 127   MOZ_ASSERT(aValue.IsNull(), "Unexpected SMIL value type");
 128
 129   aValue.mU.mPtr = nullptr;
 130   aValue.mType = this;
 131 }
 132
 133 void SMILCSSValueType::Destroy(SMILValue& aValue) const {
 134   MOZ_ASSERT(aValue.mType == this, "Unexpected SMIL value type");
 135   delete static_cast<ValueWrapper*>(aValue.mU.mPtr);
 136   aValue.mType = SMILNullType::Singleton();
 137 }
 138
 139 nsresult SMILCSSValueType::Assign(SMILValue& aDest,
 140                                   const SMILValue& aSrc) const {
 141   MOZ_ASSERT(aDest.mType == aSrc.mType, "Incompatible SMIL types");
 142   MOZ_ASSERT(aDest.mType == this, "Unexpected SMIL value type");
 143   const ValueWrapper* srcWrapper = ExtractValueWrapper(aSrc);
 144   ValueWrapper* destWrapper = ExtractValueWrapper(aDest);
 145
 146   if (srcWrapper) {
 147     if (!destWrapper) {
 148       // barely-initialized dest -- need to alloc & copy
 149       aDest.mU.mPtr = new ValueWrapper(*srcWrapper);
 150     } else {
 151       // both already fully-initialized -- just copy straight across
 152       *destWrapper = *srcWrapper;
 153     }
 154   } else if (destWrapper) {
 155     // fully-initialized dest, barely-initialized src -- clear dest
 156     delete destWrapper;
 157     aDest.mU.mPtr = destWrapper = nullptr;
 158   }  // else, both are barely-initialized -- nothing to do.
 159
 160   return NS_OK;
 161 }
 162
 163 bool SMILCSSValueType::IsEqual(const SMILValue& aLeft,
 164                                const SMILValue& aRight) const {
 165   MOZ_ASSERT(aLeft.mType == aRight.mType, "Incompatible SMIL types");
 166   MOZ_ASSERT(aLeft.mType == this, "Unexpected SMIL value");
 167   const ValueWrapper* leftWrapper = ExtractValueWrapper(aLeft);
 168   const ValueWrapper* rightWrapper = ExtractValueWrapper(aRight);
 169
 170   if (leftWrapper) {
 171     if (rightWrapper) {
 172       // Both non-null
 173       NS_WARNING_ASSERTION(leftWrapper != rightWrapper,
 174                            "Two SMILValues with matching ValueWrapper ptr");
 175       return *leftWrapper == *rightWrapper;
 176     }
 177     // Left non-null, right null
 178     return false;
 179   }
 180   if (rightWrapper) {
 181     // Left null, right non-null
 182     return false;
 183   }
 184   // Both null
 185   return true;
 186 }
 187
 188 static bool AddOrAccumulateForServo(SMILValue& aDest,
 189                                     const ValueWrapper* aValueToAddWrapper,
 190                                     ValueWrapper* aDestWrapper,
 191                                     CompositeOperation aCompositeOp,
 192                                     uint64_t aCount) {
 193   nsCSSPropertyID property =
 194       aValueToAddWrapper ? aValueToAddWrapper->mPropID : aDestWrapper->mPropID;
 195   size_t len = aValueToAddWrapper ? aValueToAddWrapper->mServoValues.Length()
 196                                   : aDestWrapper->mServoValues.Length();
 197
 198   MOZ_ASSERT(!aValueToAddWrapper || !aDestWrapper ||
 199                  aValueToAddWrapper->mServoValues.Length() ==
 200                      aDestWrapper->mServoValues.Length(),
 201              "Both of values' length in the wrappers should be the same if "
 202              "both of them exist");
 203
 204   for (size_t i = 0; i < len; i++) {
 205     const RefPtr<StyleAnimationValue>* valueToAdd =
 206         aValueToAddWrapper ? &aValueToAddWrapper->mServoValues[i] : nullptr;
 207     const RefPtr<StyleAnimationValue>* destValue =
 208         aDestWrapper ? &aDestWrapper->mServoValues[i] : nullptr;
 209     RefPtr<StyleAnimationValue> zeroValueStorage;
 210     if (!FinalizeServoAnimationValues(valueToAdd, destValue,
 211                                       zeroValueStorage)) {
 212       return false;
 213     }
 214
 215     // FinalizeServoAnimationValues may have updated destValue so we should make
 216     // sure the aDest and aDestWrapper outparams are up-to-date.
 217     if (aDestWrapper) {
 218       aDestWrapper->mServoValues[i] = *destValue;
 219     } else {
 220       // aDest may be a barely-initialized "zero" destination.
 221       aDest.mU.mPtr = aDestWrapper = new ValueWrapper(property, *destValue);
 222       aDestWrapper->mServoValues.SetLength(len);
 223     }
 224
 225     RefPtr<StyleAnimationValue> result;
 226     if (aCompositeOp == CompositeOperation::Add) {
 227       result = Servo_AnimationValues_Add(*destValue, *valueToAdd).Consume();
 228     } else {
 229       result = Servo_AnimationValues_Accumulate(*destValue, *valueToAdd, aCount)
 230                    .Consume();
 231     }
 232
 233     if (!result) {
 234       return false;
 235     }
 236     aDestWrapper->mServoValues[i] = result;
 237   }
 238
 239   return true;
 240 }
 241
 242 static bool AddOrAccumulate(SMILValue& aDest, const SMILValue& aValueToAdd,
 243                             CompositeOperation aCompositeOp, uint64_t aCount) {
 244   MOZ_ASSERT(aValueToAdd.mType == aDest.mType,
 245              "Trying to add mismatching types");
 246   MOZ_ASSERT(aValueToAdd.mType == &SMILCSSValueType::sSingleton,
 247              "Unexpected SMIL value type");
 248   MOZ_ASSERT(aCompositeOp == CompositeOperation::Add ||
 249                  aCompositeOp == CompositeOperation::Accumulate,
 250              "Composite operation should be add or accumulate");
 251   MOZ_ASSERT(aCompositeOp != CompositeOperation::Add || aCount == 1,
 252              "Count should be 1 if composite operation is add");
 253
 254   ValueWrapper* destWrapper = ExtractValueWrapper(aDest);
 255   const ValueWrapper* valueToAddWrapper = ExtractValueWrapper(aValueToAdd);
 256
 257   // If both of the values are empty just fail. This can happen in rare cases
 258   // such as when the underlying animation produced an empty value.
 259   //
 260   // Technically, it doesn't matter what we return here since in either case it
 261   // will produce the same result: an empty value.
 262   if (!destWrapper && !valueToAddWrapper) {
 263     return false;
 264   }
 265
 266   nsCSSPropertyID property =
 267       valueToAddWrapper ? valueToAddWrapper->mPropID : destWrapper->mPropID;
 268   // Special case: font-size-adjust and stroke-dasharray are explicitly
 269   // non-additive (even though StyleAnimationValue *could* support adding them)
 270   if (property == eCSSProperty_font_size_adjust ||
 271       property == eCSSProperty_stroke_dasharray) {
 272     return false;
 273   }
 274   // Skip font shorthand since it includes font-size-adjust.
 275   if (property == eCSSProperty_font) {
 276     return false;
 277   }
 278
 279   return AddOrAccumulateForServo(aDest, valueToAddWrapper, destWrapper,
 280                                  aCompositeOp, aCount);
 281 }
 282
 283 nsresult SMILCSSValueType::SandwichAdd(SMILValue& aDest,
 284                                        const SMILValue& aValueToAdd) const {
 285   return AddOrAccumulate(aDest, aValueToAdd, CompositeOperation::Add, 1)
 286              ? NS_OK
 287              : NS_ERROR_FAILURE;
 288 }
 289
 290 nsresult SMILCSSValueType::Add(SMILValue& aDest, const SMILValue& aValueToAdd,
 291                                uint32_t aCount) const {
 292   return AddOrAccumulate(aDest, aValueToAdd, CompositeOperation::Accumulate,
 293                          aCount)
 294              ? NS_OK
 295              : NS_ERROR_FAILURE;
 296 }
 297
 298 static nsresult ComputeDistanceForServo(const ValueWrapper* aFromWrapper,
 299                                         const ValueWrapper& aToWrapper,
 300                                         double& aDistance) {
 301   size_t len = aToWrapper.mServoValues.Length();
 302   MOZ_ASSERT(!aFromWrapper || aFromWrapper->mServoValues.Length() == len,
 303              "From and to values length should be the same if "
 304              "The start value exists");
 305
 306   double squareDistance = 0;
 307
 308   for (size_t i = 0; i < len; i++) {
 309     const RefPtr<StyleAnimationValue>* fromValue =
 310         aFromWrapper ? &aFromWrapper->mServoValues[0] : nullptr;
 311     const RefPtr<StyleAnimationValue>* toValue = &aToWrapper.mServoValues[0];
 312     RefPtr<StyleAnimationValue> zeroValueStorage;
 313     if (!FinalizeServoAnimationValues(fromValue, toValue, zeroValueStorage)) {
 314       return NS_ERROR_FAILURE;
 315     }
 316
 317     double distance =
 318         Servo_AnimationValues_ComputeDistance(*fromValue, *toValue);
 319     if (distance < 0.0) {
 320       return NS_ERROR_FAILURE;
 321     }
 322
 323     if (len == 1) {
 324       aDistance = distance;
 325       return NS_OK;
 326     }
 327     squareDistance += distance * distance;
 328   }
 329
 330   aDistance = sqrt(squareDistance);
 331
 332   return NS_OK;
 333 }
 334
 335 nsresult SMILCSSValueType::ComputeDistance(const SMILValue& aFrom,
 336                                            const SMILValue& aTo,
 337                                            double& aDistance) const {
 338   MOZ_ASSERT(aFrom.mType == aTo.mType, "Trying to compare different types");
 339   MOZ_ASSERT(aFrom.mType == this, "Unexpected source type");
 340
 341   const ValueWrapper* fromWrapper = ExtractValueWrapper(aFrom);
 342   const ValueWrapper* toWrapper = ExtractValueWrapper(aTo);
 343   MOZ_ASSERT(toWrapper, "expecting non-null endpoint");
 344   return ComputeDistanceForServo(fromWrapper, *toWrapper, aDistance);
 345 }
 346
 347 static nsresult InterpolateForServo(const ValueWrapper* aStartWrapper,
 348                                     const ValueWrapper& aEndWrapper,
 349                                     double aUnitDistance, SMILValue& aResult) {
 350   // For discretely-animated properties Servo_AnimationValues_Interpolate will
 351   // perform the discrete animation (i.e. 50% flip) and return a success result.
 352   // However, SMIL has its own special discrete animation behavior that it uses
 353   // when keyTimes are specified, but we won't run that unless that this method
 354   // returns a failure to indicate that the property cannot be smoothly
 355   // interpolated, i.e. that we need to use a discrete calcMode.
 356   //
 357   // For shorthands, Servo_Property_IsDiscreteAnimatable will always return
 358   // false. That's fine since most shorthands (like 'font' and
 359   // 'text-decoration') include non-discrete components. If authors want to
 360   // treat all components as discrete then they should use calcMode="discrete".
 361   if (Servo_Property_IsDiscreteAnimatable(aEndWrapper.mPropID)) {
 362     return NS_ERROR_FAILURE;
 363   }
 364
 365   ServoAnimationValues results;
 366   size_t len = aEndWrapper.mServoValues.Length();
 367   results.SetCapacity(len);
 368   MOZ_ASSERT(!aStartWrapper || aStartWrapper->mServoValues.Length() == len,
 369              "Start and end values length should be the same if "
 370              "the start value exists");
 371   for (size_t i = 0; i < len; i++) {
 372     const RefPtr<StyleAnimationValue>* startValue =
 373         aStartWrapper ? &aStartWrapper->mServoValues[i] : nullptr;
 374     const RefPtr<StyleAnimationValue>* endValue = &aEndWrapper.mServoValues[i];
 375     RefPtr<StyleAnimationValue> zeroValueStorage;
 376     if (!FinalizeServoAnimationValues(startValue, endValue, zeroValueStorage)) {
 377       return NS_ERROR_FAILURE;
 378     }
 379
 380     RefPtr<StyleAnimationValue> result =
 381         Servo_AnimationValues_Interpolate(*startValue, *endValue, aUnitDistance)
 382             .Consume();
 383     if (!result) {
 384       return NS_ERROR_FAILURE;
 385     }
 386     results.AppendElement(result);
 387   }
 388   aResult.mU.mPtr = new ValueWrapper(aEndWrapper.mPropID, std::move(results));
 389
 390   return NS_OK;
 391 }
 392
 393 nsresult SMILCSSValueType::Interpolate(const SMILValue& aStartVal,
 394                                        const SMILValue& aEndVal,
 395                                        double aUnitDistance,
 396                                        SMILValue& aResult) const {
 397   MOZ_ASSERT(aStartVal.mType == aEndVal.mType,
 398              "Trying to interpolate different types");
 399   MOZ_ASSERT(aStartVal.mType == this, "Unexpected types for interpolation");
 400   MOZ_ASSERT(aResult.mType == this, "Unexpected result type");
 401   MOZ_ASSERT(aUnitDistance >= 0.0 && aUnitDistance <= 1.0,
 402              "unit distance value out of bounds");
 403   MOZ_ASSERT(!aResult.mU.mPtr, "expecting barely-initialized outparam");
 404
 405   const ValueWrapper* startWrapper = ExtractValueWrapper(aStartVal);
 406   const ValueWrapper* endWrapper = ExtractValueWrapper(aEndVal);
 407   MOZ_ASSERT(endWrapper, "expecting non-null endpoint");
 408   return InterpolateForServo(startWrapper, *endWrapper, aUnitDistance, aResult);
 409 }
 410
 411 static ServoAnimationValues ValueFromStringHelper(
 412     nsCSSPropertyID aPropID, Element* aTargetElement,
 413     nsPresContext* aPresContext, const ComputedStyle* aComputedStyle,
 414     const nsAString& aString) {
 415   ServoAnimationValues result;
 416
 417   Document* doc = aTargetElement->GetComposedDoc();
 418   if (!doc) {
 419     return result;
 420   }
 421
 422   // Parse property
 423   ServoCSSParser::ParsingEnvironment env =
 424       ServoCSSParser::GetParsingEnvironment(doc);
 425   RefPtr<StyleLockedDeclarationBlock> servoDeclarationBlock =
 426       ServoCSSParser::ParseProperty(aPropID, NS_ConvertUTF16toUTF8(aString),
 427                                     env,
 428                                     ParsingMode::AllowUnitlessLength |
 429                                         ParsingMode::AllowAllNumericValues);
 430   if (!servoDeclarationBlock) {
 431     return result;
 432   }
 433
 434   // Compute value
 435   aPresContext->StyleSet()->GetAnimationValues(
 436       servoDeclarationBlock, aTargetElement, aComputedStyle, result);
 437
 438   return result;
 439 }
 440
 441 // static
 442 void SMILCSSValueType::ValueFromString(nsCSSPropertyID aPropID,
 443                                        Element* aTargetElement,
 444                                        const nsAString& aString,
 445                                        SMILValue& aValue,
 446                                        bool* aIsContextSensitive) {
 447   MOZ_ASSERT(aValue.IsNull(), "Outparam should be null-typed");
 448   nsPresContext* presContext =
 449       nsContentUtils::GetContextForContent(aTargetElement);
 450   if (!presContext) {
 451     NS_WARNING("Not parsing animation value; unable to get PresContext");
 452     return;
 453   }
 454
 455   Document* doc = aTargetElement->GetComposedDoc();
 456   if (doc && !nsStyleUtil::CSPAllowsInlineStyle(nullptr, doc, nullptr, 0, 0,
 457                                                 aString, nullptr)) {
 458     return;
 459   }
 460
 461   RefPtr<const ComputedStyle> computedStyle =
 462       nsComputedDOMStyle::GetComputedStyle(aTargetElement);
 463   if (!computedStyle) {
 464     return;
 465   }
 466
 467   ServoAnimationValues parsedValues = ValueFromStringHelper(
 468       aPropID, aTargetElement, presContext, computedStyle, aString);
 469   if (aIsContextSensitive) {
 470     // FIXME: Bug 1358955 - detect context-sensitive values and set this value
 471     // appropriately.
 472     *aIsContextSensitive = false;
 473   }
 474
 475   if (!parsedValues.IsEmpty()) {
 476     sSingleton.Init(aValue);
 477     aValue.mU.mPtr = new ValueWrapper(aPropID, std::move(parsedValues));
 478   }
 479 }
 480
 481 // static
 482 SMILValue SMILCSSValueType::ValueFromAnimationValue(
 483     nsCSSPropertyID aPropID, Element* aTargetElement,
 484     const AnimationValue& aValue) {
 485   SMILValue result;
 486
 487   Document* doc = aTargetElement->GetComposedDoc();
 488   // We'd like to avoid serializing |aValue| if possible, and since the
 489   // string passed to CSPAllowsInlineStyle is only used for reporting violations
 490   // and an intermediate CSS value is not likely to be particularly useful
 491   // in that case, we just use a generic placeholder string instead.
 492   static const nsLiteralString kPlaceholderText = u"[SVG animation of CSS]"_ns;
 493   if (doc && !nsStyleUtil::CSPAllowsInlineStyle(nullptr, doc, nullptr, 0, 0,
 494                                                 kPlaceholderText, nullptr)) {
 495     return result;
 496   }
 497
 498   sSingleton.Init(result);
 499   result.mU.mPtr = new ValueWrapper(aPropID, aValue);
 500
 501   return result;
 502 }
 503
 504 // static
 505 bool SMILCSSValueType::SetPropertyValues(const SMILValue& aValue,
 506                                          DeclarationBlock& aDecl) {
 507   MOZ_ASSERT(aValue.mType == &SMILCSSValueType::sSingleton,
 508              "Unexpected SMIL value type");
 509   const ValueWrapper* wrapper = ExtractValueWrapper(aValue);
 510   if (!wrapper) {
 511     return false;
 512   }
 513
 514   bool changed = false;
 515   for (const auto& value : wrapper->mServoValues) {
 516     changed |= Servo_DeclarationBlock_SetPropertyToAnimationValue(aDecl.Raw(),
 517                                                                   value, {});
 518   }
 519
 520   return changed;
 521 }
 522
 523 // static
 524 nsCSSPropertyID SMILCSSValueType::PropertyFromValue(const SMILValue& aValue) {
 525   if (aValue.mType != &SMILCSSValueType::sSingleton) {
 526     return eCSSProperty_UNKNOWN;
 527   }
 528
 529   const ValueWrapper* wrapper = ExtractValueWrapper(aValue);
 530   if (!wrapper) {
 531     return eCSSProperty_UNKNOWN;
 532   }
 533
 534   return wrapper->mPropID;
 535 }
 536
 537 // static
 538 void SMILCSSValueType::FinalizeValue(SMILValue& aValue,
 539                                      const SMILValue& aValueToMatch) {
 540   MOZ_ASSERT(aValue.mType == aValueToMatch.mType, "Incompatible SMIL types");
 541   MOZ_ASSERT(aValue.mType == &SMILCSSValueType::sSingleton,
 542              "Unexpected SMIL value type");
 543
 544   ValueWrapper* valueWrapper = ExtractValueWrapper(aValue);
 545   // If |aValue| already has a value, there's nothing to do here.
 546   if (valueWrapper) {
 547     return;
 548   }
 549
 550   const ValueWrapper* valueToMatchWrapper = ExtractValueWrapper(aValueToMatch);
 551   if (!valueToMatchWrapper) {
 552     MOZ_ASSERT_UNREACHABLE("Value to match is empty");
 553     return;
 554   }
 555
 556   ServoAnimationValues zeroValues;
 557   zeroValues.SetCapacity(valueToMatchWrapper->mServoValues.Length());
 558
 559   for (const auto& valueToMatch : valueToMatchWrapper->mServoValues) {
 560     RefPtr<StyleAnimationValue> zeroValue =
 561         Servo_AnimationValues_GetZeroValue(valueToMatch).Consume();
 562     if (!zeroValue) {
 563       return;
 564     }
 565     zeroValues.AppendElement(std::move(zeroValue));
 566   }
 567   aValue.mU.mPtr =
 568       new ValueWrapper(valueToMatchWrapper->mPropID, std::move(zeroValues));
 569 }
 570
 571 }  // namespace mozilla