Implement aspect-ratio interpolation support.

Based on the discussion in w3c/csswg-drafts#4953
aspect ratios should be interpolated by the log of their value preserving
the same visual speed whether they are wide or narrow.

This patch adds a new interpolation type for aspect ratios and uses it
for interpolating the CSS aspect-ratio property.

Bug: 1156160
Change-Id: I6cbff0abef54290de559a7625e24e3c4e1f1e0e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2586234
Reviewed-by: Kevin Ellis <kevers@chromium.org>
Reviewed-by: Xida Chen <xidachen@chromium.org>
Commit-Queue: Robert Flack <flackr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#846135}

third_party/blink/renderer/core/animation/BUILD.gn

@@ -72,6 +72,8 @@ blink_core_sources("animation") {
     "css/css_transition_data.h",
     "css_angle_interpolation_type.cc",
     "css_angle_interpolation_type.h",
+    "css_aspect_ratio_interpolation_type.cc",
+    "css_aspect_ratio_interpolation_type.h",
     "css_basic_shape_interpolation_type.cc",
     "css_basic_shape_interpolation_type.h",
     "css_border_image_length_box_interpolation_type.cc",
@@ -168,6 +170,8 @@ blink_core_sources("animation") {
     "image_slice_property_functions.h",
     "inert_effect.cc",
     "inert_effect.h",
+    "interpolable_aspect_ratio.cc",
+    "interpolable_aspect_ratio.h",
     "interpolable_filter.cc",
     "interpolable_filter.h",
     "interpolable_length.cc",

third_party/blink/renderer/core/animation/css_aspect_ratio_interpolation_type.cc

@@ -0,0 +1,164 @@
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "third_party/blink/renderer/core/animation/css_aspect_ratio_interpolation_type.h"
+
+#include <memory>
+#include <utility>
+
+#include "base/memory/ptr_util.h"
+#include "third_party/blink/renderer/core/animation/interpolable_aspect_ratio.h"
+#include "third_party/blink/renderer/core/css/resolver/style_builder_converter.h"
+#include "third_party/blink/renderer/core/css/resolver/style_resolver_state.h"
+#include "third_party/blink/renderer/core/style/computed_style.h"
+#include "third_party/blink/renderer/core/style/style_aspect_ratio.h"
+
+namespace blink {
+
+class CSSAspectRatioNonInterpolableValue final : public NonInterpolableValue {
+ public:
+  ~CSSAspectRatioNonInterpolableValue() final = default;
+
+  static scoped_refptr<CSSAspectRatioNonInterpolableValue> Create(
+      StyleAspectRatio aspect_ratio) {
+    return base::AdoptRef(
+        new CSSAspectRatioNonInterpolableValue(aspect_ratio.GetType()));
+  }
+
+  EAspectRatioType GetAspectRatioType() const { return type_; }
+
+  bool IsCompatibleWith(const CSSAspectRatioNonInterpolableValue& other) const {
+    if (GetAspectRatioType() == EAspectRatioType::kAuto ||
+        GetAspectRatioType() != other.GetAspectRatioType())
+      return false;
+    return true;
+  }
+
+  DECLARE_NON_INTERPOLABLE_VALUE_TYPE();
+
+ private:
+  explicit CSSAspectRatioNonInterpolableValue(EAspectRatioType type)
+      : type_(type) {}
+
+  EAspectRatioType type_;
+};
+
+DEFINE_NON_INTERPOLABLE_VALUE_TYPE(CSSAspectRatioNonInterpolableValue);
+template <>
+struct DowncastTraits<CSSAspectRatioNonInterpolableValue> {
+  static bool AllowFrom(const NonInterpolableValue* value) {
+    return value && AllowFrom(*value);
+  }
+  static bool AllowFrom(const NonInterpolableValue& value) {
+    return value.GetType() == CSSAspectRatioNonInterpolableValue::static_type_;
+  }
+};
+
+class InheritedAspectRatioChecker
+    : public CSSInterpolationType::CSSConversionChecker {
+ public:
+  explicit InheritedAspectRatioChecker(StyleAspectRatio aspect_ratio)
+      : aspect_ratio_(aspect_ratio) {}
+
+ private:
+  bool IsValid(const StyleResolverState& state,
+               const InterpolationValue& underlying) const final {
+    return state.ParentStyle()->AspectRatio() == aspect_ratio_;
+  }
+
+  const StyleAspectRatio aspect_ratio_;
+};
+
+std::unique_ptr<InterpolableValue>
+CSSAspectRatioInterpolationType::CreateInterpolableAspectRatio(
+    const StyleAspectRatio& aspect_ratio) {
+  std::unique_ptr<InterpolableAspectRatio> result =
+      InterpolableAspectRatio::MaybeCreate(aspect_ratio);
+  return std::move(result);
+}
+
+PairwiseInterpolationValue CSSAspectRatioInterpolationType::MaybeMergeSingles(
+    InterpolationValue&& start,
+    InterpolationValue&& end) const {
+  if (!To<CSSAspectRatioNonInterpolableValue>(*start.non_interpolable_value)
+           .IsCompatibleWith(To<CSSAspectRatioNonInterpolableValue>(
+               *end.non_interpolable_value))) {
+    return nullptr;
+  }
+  return PairwiseInterpolationValue(std::move(start.interpolable_value),
+                                    std::move(end.interpolable_value),
+                                    std::move(start.non_interpolable_value));
+}
+
+InterpolationValue CSSAspectRatioInterpolationType::MaybeConvertNeutral(
+    const InterpolationValue& underlying,
+    ConversionCheckers& conversion_checkers) const {
+  return InterpolationValue(underlying.interpolable_value->CloneAndZero(),
+                            underlying.non_interpolable_value);
+}
+
+InterpolationValue CSSAspectRatioInterpolationType::MaybeConvertInitial(
+    const StyleResolverState&,
+    ConversionCheckers& conversion_checkers) const {
+  StyleAspectRatio initial_ratio = ComputedStyle::InitialStyle().AspectRatio();
+  return InterpolationValue(
+      CreateInterpolableAspectRatio(initial_ratio),
+      CSSAspectRatioNonInterpolableValue::Create(initial_ratio));
+}
+
+InterpolationValue CSSAspectRatioInterpolationType::MaybeConvertInherit(
+    const StyleResolverState& state,
+    ConversionCheckers& conversion_checkers) const {
+  if (!state.ParentStyle())
+    return nullptr;
+
+  StyleAspectRatio inherited_aspect_ratio = state.ParentStyle()->AspectRatio();
+  conversion_checkers.push_back(
+      std::make_unique<InheritedAspectRatioChecker>(inherited_aspect_ratio));
+  if (inherited_aspect_ratio.IsAuto())
+    return nullptr;
+
+  return InterpolationValue(
+      CreateInterpolableAspectRatio(inherited_aspect_ratio),
+      CSSAspectRatioNonInterpolableValue::Create(inherited_aspect_ratio));
+}
+
+InterpolationValue
+CSSAspectRatioInterpolationType::MaybeConvertStandardPropertyUnderlyingValue(
+    const ComputedStyle& style) const {
+  return InterpolationValue(
+      CreateInterpolableAspectRatio(style.AspectRatio()),
+      CSSAspectRatioNonInterpolableValue::Create(style.AspectRatio()));
+}
+
+InterpolationValue CSSAspectRatioInterpolationType::MaybeConvertValue(
+    const CSSValue& value,
+    const StyleResolverState* state,
+    ConversionCheckers&) const {
+  StyleAspectRatio ratio =
+      StyleBuilderConverter::ConvertAspectRatio(*state, value);
+  return InterpolationValue(CreateInterpolableAspectRatio(ratio),
+                            CSSAspectRatioNonInterpolableValue::Create(ratio));
+}
+
+void CSSAspectRatioInterpolationType::ApplyStandardPropertyValue(
+    const InterpolableValue& interpolable_value,
+    const NonInterpolableValue* non_interpolable_value,
+    StyleResolverState& state) const {
+  const auto& aspect_ratio = To<InterpolableAspectRatio>(interpolable_value);
+  state.Style()->SetAspectRatio(StyleAspectRatio(
+      To<CSSAspectRatioNonInterpolableValue>(non_interpolable_value)
+          ->GetAspectRatioType(),
+      aspect_ratio.GetRatio()));
+}
+void CSSAspectRatioInterpolationType::Composite(
+    UnderlyingValueOwner& underlying_value_owner,
+    double underlying_fraction,
+    const InterpolationValue& value,
+    double interpolation_fraction) const {
+  underlying_value_owner.MutableValue().interpolable_value->ScaleAndAdd(
+      underlying_fraction, *value.interpolable_value);
+}
+
+}  // namespace blink

third_party/blink/renderer/core/animation/css_aspect_ratio_interpolation_type.h

@@ -0,0 +1,53 @@
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_CSS_ASPECT_RATIO_INTERPOLATION_TYPE_H_
+#define THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_CSS_ASPECT_RATIO_INTERPOLATION_TYPE_H_
+
+#include "third_party/blink/renderer/core/animation/css_interpolation_type.h"
+#include "third_party/blink/renderer/core/css_value_keywords.h"
+
+namespace blink {
+
+class StyleAspectRatio;
+
+class CSSAspectRatioInterpolationType : public CSSInterpolationType {
+ public:
+  explicit CSSAspectRatioInterpolationType(PropertyHandle property)
+      : CSSInterpolationType(property) {
+    DCHECK_EQ(CSSPropertyID::kAspectRatio,
+              property.GetCSSProperty().PropertyID());
+  }
+
+  InterpolationValue MaybeConvertStandardPropertyUnderlyingValue(
+      const ComputedStyle&) const final;
+  PairwiseInterpolationValue MaybeMergeSingles(
+      InterpolationValue&& start,
+      InterpolationValue&& end) const final;
+  void ApplyStandardPropertyValue(const InterpolableValue&,
+                                  const NonInterpolableValue*,
+                                  StyleResolverState&) const final;
+  void Composite(UnderlyingValueOwner&,
+                 double underlying_fraction,
+                 const InterpolationValue&,
+                 double interpolation_fraction) const final;
+
+  static std::unique_ptr<InterpolableValue> CreateInterpolableAspectRatio(
+      const StyleAspectRatio&);
+
+ private:
+  InterpolationValue MaybeConvertNeutral(const InterpolationValue& underlying,
+                                         ConversionCheckers&) const final;
+  InterpolationValue MaybeConvertInitial(const StyleResolverState&,
+                                         ConversionCheckers&) const final;
+  InterpolationValue MaybeConvertInherit(const StyleResolverState&,
+                                         ConversionCheckers&) const final;
+  InterpolationValue MaybeConvertValue(const CSSValue&,
+                                       const StyleResolverState*,
+                                       ConversionCheckers&) const final;
+};
+
+}  // namespace blink
+
+#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_CSS_ASPECT_RATIO_INTERPOLATION_TYPE_H_

third_party/blink/renderer/core/animation/css_interpolation_types_map.cc

@@ -9,6 +9,7 @@
 
 #include "third_party/blink/public/mojom/feature_policy/feature_policy_feature.mojom-blink.h"
 #include "third_party/blink/renderer/core/animation/css_angle_interpolation_type.h"
+#include "third_party/blink/renderer/core/animation/css_aspect_ratio_interpolation_type.h"
 #include "third_party/blink/renderer/core/animation/css_basic_shape_interpolation_type.h"
 #include "third_party/blink/renderer/core/animation/css_border_image_length_box_interpolation_type.h"
 #include "third_party/blink/renderer/core/animation/css_clip_interpolation_type.h"
@@ -179,6 +180,10 @@ const InterpolationTypes& CSSInterpolationTypesMap::Get(
         applicable_types->push_back(
             std::make_unique<CSSLengthInterpolationType>(used_property));
         break;
+      case CSSPropertyID::kAspectRatio:
+        applicable_types->push_back(
+            std::make_unique<CSSAspectRatioInterpolationType>(used_property));
+        break;
       case CSSPropertyID::kFlexGrow:
       case CSSPropertyID::kFlexShrink:
       case CSSPropertyID::kFillOpacity:

third_party/blink/renderer/core/animation/interpolable_aspect_ratio.cc

@@ -0,0 +1,65 @@
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "third_party/blink/renderer/core/animation/interpolable_aspect_ratio.h"
+#include "third_party/blink/renderer/core/animation/interpolable_value.h"
+#include "third_party/blink/renderer/core/css/resolver/style_resolver_state.h"
+#include "third_party/blink/renderer/core/style/style_aspect_ratio.h"
+#include "third_party/blink/renderer/platform/runtime_enabled_features.h"
+
+namespace blink {
+
+// static
+std::unique_ptr<InterpolableAspectRatio> InterpolableAspectRatio::MaybeCreate(
+    const StyleAspectRatio& aspect_ratio) {
+  if (!RuntimeEnabledFeatures::CSSAspectRatioInterpolationEnabled())
+    return nullptr;
+
+  // Auto aspect ratio cannot be interpolated to / from.
+  if (aspect_ratio.IsAuto())
+    return nullptr;
+  return std::make_unique<InterpolableAspectRatio>(aspect_ratio.GetRatio());
+}
+
+InterpolableAspectRatio::InterpolableAspectRatio(
+    const FloatSize& aspect_ratio) {
+  // The StyleAspectRatio::IsAuto check in MaybeCreate should return true if we
+  // have a degenerate aspect ratio.
+  DCHECK(aspect_ratio.Height() > 0 && aspect_ratio.Width() > 0);
+
+  value_ = std::make_unique<InterpolableNumber>(
+      log(aspect_ratio.Width() / aspect_ratio.Height()));
+}
+
+FloatSize InterpolableAspectRatio::GetRatio() const {
+  return FloatSize(exp(To<InterpolableNumber>(*value_).Value()), 1);
+}
+
+void InterpolableAspectRatio::Scale(double scale) {
+  value_->Scale(scale);
+}
+
+void InterpolableAspectRatio::Add(const InterpolableValue& other) {
+  value_->Add(*To<InterpolableAspectRatio>(other).value_);
+}
+
+void InterpolableAspectRatio::AssertCanInterpolateWith(
+    const InterpolableValue& other) const {
+  const InterpolableAspectRatio& other_aspect_ratio =
+      To<InterpolableAspectRatio>(other);
+  value_->AssertCanInterpolateWith(*other_aspect_ratio.value_);
+}
+
+void InterpolableAspectRatio::Interpolate(const InterpolableValue& to,
+                                          const double progress,
+                                          InterpolableValue& result) const {
+  const InterpolableAspectRatio& aspect_ratio_to =
+      To<InterpolableAspectRatio>(to);
+  InterpolableAspectRatio& aspect_ratio_result =
+      To<InterpolableAspectRatio>(result);
+  value_->Interpolate(*aspect_ratio_to.value_, progress,
+                      *aspect_ratio_result.value_);
+}
+
+}  // namespace blink

third_party/blink/renderer/core/animation/interpolable_aspect_ratio.h

@@ -0,0 +1,62 @@
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_INTERPOLABLE_ASPECT_RATIO_H_
+#define THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_INTERPOLABLE_ASPECT_RATIO_H_
+
+#include <memory>
+#include "third_party/blink/renderer/core/animation/interpolable_value.h"
+#include "third_party/blink/renderer/core/style/style_aspect_ratio.h"
+
+namespace blink {
+
+// Represents a blink::StyleAspectRatio, converted into its logarithm for
+// interpolation.
+class CORE_EXPORT InterpolableAspectRatio final : public InterpolableValue {
+ public:
+  explicit InterpolableAspectRatio(const FloatSize& ratio);
+  explicit InterpolableAspectRatio(std::unique_ptr<InterpolableValue> value)
+      : value_(std::move(value)) {}
+
+  static std::unique_ptr<InterpolableAspectRatio> MaybeCreate(
+      const StyleAspectRatio&);
+
+  FloatSize GetRatio() const;
+
+  // InterpolableValue implementation:
+  void Interpolate(const InterpolableValue& to,
+                   const double progress,
+                   InterpolableValue& result) const final;
+  bool IsAspectRatio() const final { return true; }
+  bool Equals(const InterpolableValue& other) const final {
+    NOTREACHED();
+    return false;
+  }
+  void Scale(double scale) final;
+  void Add(const InterpolableValue& other) final;
+  void AssertCanInterpolateWith(const InterpolableValue& other) const final;
+
+ private:
+  InterpolableAspectRatio* RawClone() const final {
+    return new InterpolableAspectRatio(value_->Clone());
+  }
+  InterpolableAspectRatio* RawCloneAndZero() const final {
+    return new InterpolableAspectRatio(value_->CloneAndZero());
+  }
+
+  // Interpolable aspect ratio value is stored and interpolated as the log of
+  // the real aspect ratio.
+  std::unique_ptr<InterpolableValue> value_;
+};
+
+template <>
+struct DowncastTraits<InterpolableAspectRatio> {
+  static bool AllowFrom(const InterpolableValue& interpolable_value) {
+    return interpolable_value.IsAspectRatio();
+  }
+};
+
+}  // namespace blink
+
+#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_INTERPOLABLE_ASPECT_RATIO_H_

third_party/blink/renderer/core/animation/interpolable_value.h

@@ -39,6 +39,7 @@ class CORE_EXPORT InterpolableValue {
   virtual bool IsBool() const { return false; }
   virtual bool IsList() const { return false; }
   virtual bool IsLength() const { return false; }
+  virtual bool IsAspectRatio() const { return false; }
   virtual bool IsShadow() const { return false; }
   virtual bool IsFilter() const { return false; }
   virtual bool IsTransformList() const { return false; }