[web-animations] WPT test css/CSS2/visufx/animation/visibility-interp…

…olation.html is a unique failure

https://bugs.webkit.org/show_bug.cgi?id=270434

Reviewed by Antti Koivisto.

Interpolation of the "visibility" property is discrete when neither of the values for a given
animation interval is "visible", per https://drafts.csswg.org/web-animations-1/#animating-visibility.

This addresses the final failures in this test.

* LayoutTests/imported/w3c/web-platform-tests/css/CSS2/visufx/animation/visibility-interpolation-expected.txt:
* Source/WebCore/animation/CSSPropertyAnimation.cpp:
(WebCore::blendFunc):
(WebCore::CSSPropertyAnimationWrapperMap::CSSPropertyAnimationWrapperMap):

Canonical link: https://commits.webkit.org/275636@main

LayoutTests/imported/w3c/web-platform-tests/css/CSS2/visufx/animation/visibility-interpolation-expected.txt

@@ -91,16 +91,16 @@ PASS Web Animations: property <visibility> from [collapse] to [visible] at (0.1)
 PASS Web Animations: property <visibility> from [collapse] to [visible] at (0.9) should be [visible]
 PASS Web Animations: property <visibility> from [collapse] to [visible] at (1) should be [visible]
 PASS Web Animations: property <visibility> from [collapse] to [visible] at (1.5) should be [visible]
-FAIL CSS Transitions: property <visibility> from [collapse] to [hidden] at (-0.3) should be [hidden] assert_equals: expected "hidden " but got "collapse "
-FAIL CSS Transitions: property <visibility> from [collapse] to [hidden] at (0) should be [hidden] assert_equals: expected "hidden " but got "collapse "
-FAIL CSS Transitions: property <visibility> from [collapse] to [hidden] at (0.3) should be [hidden] assert_equals: expected "hidden " but got "collapse "
+PASS CSS Transitions: property <visibility> from [collapse] to [hidden] at (-0.3) should be [hidden]
+PASS CSS Transitions: property <visibility> from [collapse] to [hidden] at (0) should be [hidden]
+PASS CSS Transitions: property <visibility> from [collapse] to [hidden] at (0.3) should be [hidden]
 PASS CSS Transitions: property <visibility> from [collapse] to [hidden] at (0.5) should be [hidden]
 PASS CSS Transitions: property <visibility> from [collapse] to [hidden] at (0.6) should be [hidden]
 PASS CSS Transitions: property <visibility> from [collapse] to [hidden] at (1) should be [hidden]
 PASS CSS Transitions: property <visibility> from [collapse] to [hidden] at (1.5) should be [hidden]
-FAIL CSS Transitions with transition: all: property <visibility> from [collapse] to [hidden] at (-0.3) should be [hidden] assert_equals: expected "hidden " but got "collapse "
-FAIL CSS Transitions with transition: all: property <visibility> from [collapse] to [hidden] at (0) should be [hidden] assert_equals: expected "hidden " but got "collapse "
-FAIL CSS Transitions with transition: all: property <visibility> from [collapse] to [hidden] at (0.3) should be [hidden] assert_equals: expected "hidden " but got "collapse "
+PASS CSS Transitions with transition: all: property <visibility> from [collapse] to [hidden] at (-0.3) should be [hidden]
+PASS CSS Transitions with transition: all: property <visibility> from [collapse] to [hidden] at (0) should be [hidden]
+PASS CSS Transitions with transition: all: property <visibility> from [collapse] to [hidden] at (0.3) should be [hidden]
 PASS CSS Transitions with transition: all: property <visibility> from [collapse] to [hidden] at (0.5) should be [hidden]
 PASS CSS Transitions with transition: all: property <visibility> from [collapse] to [hidden] at (0.6) should be [hidden]
 PASS CSS Transitions with transition: all: property <visibility> from [collapse] to [hidden] at (1) should be [hidden]

Source/WebCore/animation/CSSPropertyAnimation.cpp

@@ -361,8 +361,10 @@ static inline ContentVisibility blendFunc(ContentVisibility from, ContentVisibil
 
 static inline Visibility blendFunc(Visibility from, Visibility to, const CSSPropertyBlendingContext& context)
 {
-    if (from != Visibility::Visible && to != Visibility::Visible)
-        return context.progress < 0.5 ? from : to;
+    if (context.isDiscrete) {
+        ASSERT(!context.progress || context.progress == 1.0);
+        return context.progress ? to : from;
+    }
 
     // Any non-zero result means we consider the object to be visible. Only at 0 do we consider the object to be
     // invisible. The invisible value we use (Visibility::Hidden vs. Visibility::Collapse) depends on the specified from/to values.
@@ -3469,6 +3471,25 @@ class QuotesWrapper final : public AnimationPropertyWrapperBase {
 };
 DEFINE_ALLOCATOR_WITH_HEAP_IDENTIFIER(QuotesWrapper);
 
+DECLARE_ALLOCATOR_WITH_HEAP_IDENTIFIER(VisibilityWrapper);
+class VisibilityWrapper final : public PropertyWrapper<Visibility> {
+    WTF_MAKE_FAST_ALLOCATED_WITH_HEAP_IDENTIFIER(VisibilityWrapper);
+public:
+    VisibilityWrapper()
+        : PropertyWrapper(CSSPropertyVisibility, &RenderStyle::visibility, &RenderStyle::setVisibility)
+    {
+    }
+
+private:
+    bool canInterpolate(const RenderStyle& from, const RenderStyle& to, CompositeOperation) const final
+    {
+        // https://drafts.csswg.org/web-animations-1/#animating-visibility
+        // If neither value is visible, then discrete animation is used.
+        return value(from) == Visibility::Visible || value(to) == Visibility::Visible;
+    }
+};
+DEFINE_ALLOCATOR_WITH_HEAP_IDENTIFIER(VisibilityWrapper);
+
 template <typename T>
 class DiscreteSVGPropertyWrapper final : public AnimationPropertyWrapperBase {
     WTF_MAKE_FAST_ALLOCATED;
@@ -3677,7 +3698,7 @@ CSSPropertyAnimationWrapperMap::CSSPropertyAnimationWrapperMap()
         new LengthVariantPropertyWrapper<LengthSize>(CSSPropertyBorderTopRightRadius, &RenderStyle::borderTopRightRadius, &RenderStyle::setBorderTopRightRadius),
         new LengthVariantPropertyWrapper<LengthSize>(CSSPropertyBorderBottomLeftRadius, &RenderStyle::borderBottomLeftRadius, &RenderStyle::setBorderBottomLeftRadius),
         new LengthVariantPropertyWrapper<LengthSize>(CSSPropertyBorderBottomRightRadius, &RenderStyle::borderBottomRightRadius, &RenderStyle::setBorderBottomRightRadius),
-        new PropertyWrapper<Visibility>(CSSPropertyVisibility, &RenderStyle::visibility, &RenderStyle::setVisibility),
+        new VisibilityWrapper,
 
         new ClipWrapper,