Attachment 349310 Details for Bug 176454 – WIP Patch (CSS parsing only)

[patch] WIP Patch (CSS parsing only)

0001-Bug-176454-Implement-CSS-overscroll-behavior.patch (text/plain), 67.14 KB, created by Frédéric Wang (:fredw) on 2018-09-10 08:07:48 PDT

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Description:

Filename:

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Creator: Frédéric Wang (:fredw)

Created: 2018-09-10 08:07:48 PDT

Size: 67.14 KB

patch

obsolete

>From 4547bc436934aba3978f01cec9e9843ba20808ec Mon Sep 17 00:00:00 2001
>From: Frederic Wang <fwang@igalia.com>
>Date: Fri, 7 Sep 2018 20:32:36 +0200
>Subject: [PATCH xserver] Bug 176454 - Implement CSS overscroll-behavior
>
>---
> .../Configurations/FeatureDefines.xcconfig    |  4 +-
> Source/WTF/wtf/FeatureDefines.h               |  4 ++
> .../Configurations/FeatureDefines.xcconfig    |  4 +-
> .../Configurations/FeatureDefines.xcconfig    |  4 +-
> .../css/CSSComputedStyleDeclaration.cpp       | 12 ++++++
> .../WebCore/css/CSSPrimitiveValueMappings.h   | 38 +++++++++++++++++++
> Source/WebCore/css/CSSProperties.json         | 38 +++++++++++++++++++
> Source/WebCore/css/CSSValueKeywords.in        |  5 +++
> .../WebCore/css/parser/CSSParserFastPaths.cpp |  9 +++++
> Source/WebCore/rendering/style/RenderStyle.h  | 13 +++++++
> .../rendering/style/RenderStyleConstants.h    |  8 ++++
> .../style/StyleRareNonInheritedData.cpp       | 12 ++++++
> .../style/StyleRareNonInheritedData.h         |  5 +++
> .../Configurations/FeatureDefines.xcconfig    |  4 +-
> .../Configurations/FeatureDefines.xcconfig    |  4 +-
> Source/cmake/WebKitFeatures.cmake             |  1 +
> .../cmake/tools/vsprops/FeatureDefines.props  |  7 +++-
> .../tools/vsprops/FeatureDefinesCairo.props   |  7 +++-
> Tools/Scripts/webkitperl/FeatureList.pm       |  4 ++
> .../Configurations/FeatureDefines.xcconfig    |  4 +-
> 20 files changed, 179 insertions(+), 8 deletions(-)
>
>diff --git a/Source/JavaScriptCore/Configurations/FeatureDefines.xcconfig b/Source/JavaScriptCore/Configurations/FeatureDefines.xcconfig
>index dfa4a259773..e71d666aab4 100644
>--- a/Source/JavaScriptCore/Configurations/FeatureDefines.xcconfig
>+++ b/Source/JavaScriptCore/Configurations/FeatureDefines.xcconfig
>@@ -40,6 +40,8 @@ ENABLE_ACCELERATED_2D_CANVAS = ;
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING = $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING_$(WK_COCOA_TOUCH));
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING_cocoatouch = ENABLE_ACCELERATED_OVERFLOW_SCROLLING;
> 
>+ENABLE_CSSOM_OVERSCROLL_BEHAVIOR = ENABLE_CSSOM_OVERSCROLL_BEHAVIOR;
>+
> ENABLE_APPLE_PAY = $(ENABLE_APPLE_PAY_$(WK_PLATFORM_NAME));
> ENABLE_APPLE_PAY_iphoneos = ENABLE_APPLE_PAY;
> ENABLE_APPLE_PAY_iphonesimulator = ENABLE_APPLE_PAY;
>@@ -374,4 +376,4 @@ ENABLE_WIRELESS_PLAYBACK_TARGET = ENABLE_WIRELESS_PLAYBACK_TARGET;
> 
> ENABLE_XSLT = ENABLE_XSLT;
> 
>-FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>+FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_CSSOM_OVERSCROLL_BEHAVIOR) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>diff --git a/Source/WTF/wtf/FeatureDefines.h b/Source/WTF/wtf/FeatureDefines.h
>index 5e1291d20d3..30773df4a83 100644
>--- a/Source/WTF/wtf/FeatureDefines.h
>+++ b/Source/WTF/wtf/FeatureDefines.h
>@@ -361,6 +361,10 @@ the public iOS SDK. See <https://webkit.org/b/179167>. */
> #define ENABLE_ACCELERATED_OVERFLOW_SCROLLING 0
> #endif
> 
>+#if !defined(ENABLE_CSSOM_OVERSCROLL_BEHAVIOR)
>+#define ENABLE_CSSOM_OVERSCROLL_BEHAVIOR 1
>+#endif
>+
> #if !defined(ENABLE_APNG)
> #define ENABLE_APNG 1
> #endif
>diff --git a/Source/WebCore/Configurations/FeatureDefines.xcconfig b/Source/WebCore/Configurations/FeatureDefines.xcconfig
>index dfa4a259773..e71d666aab4 100644
>--- a/Source/WebCore/Configurations/FeatureDefines.xcconfig
>+++ b/Source/WebCore/Configurations/FeatureDefines.xcconfig
>@@ -40,6 +40,8 @@ ENABLE_ACCELERATED_2D_CANVAS = ;
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING = $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING_$(WK_COCOA_TOUCH));
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING_cocoatouch = ENABLE_ACCELERATED_OVERFLOW_SCROLLING;
> 
>+ENABLE_CSSOM_OVERSCROLL_BEHAVIOR = ENABLE_CSSOM_OVERSCROLL_BEHAVIOR;
>+
> ENABLE_APPLE_PAY = $(ENABLE_APPLE_PAY_$(WK_PLATFORM_NAME));
> ENABLE_APPLE_PAY_iphoneos = ENABLE_APPLE_PAY;
> ENABLE_APPLE_PAY_iphonesimulator = ENABLE_APPLE_PAY;
>@@ -374,4 +376,4 @@ ENABLE_WIRELESS_PLAYBACK_TARGET = ENABLE_WIRELESS_PLAYBACK_TARGET;
> 
> ENABLE_XSLT = ENABLE_XSLT;
> 
>-FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>+FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_CSSOM_OVERSCROLL_BEHAVIOR) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>diff --git a/Source/WebCore/PAL/Configurations/FeatureDefines.xcconfig b/Source/WebCore/PAL/Configurations/FeatureDefines.xcconfig
>index dfa4a259773..e71d666aab4 100644
>--- a/Source/WebCore/PAL/Configurations/FeatureDefines.xcconfig
>+++ b/Source/WebCore/PAL/Configurations/FeatureDefines.xcconfig
>@@ -40,6 +40,8 @@ ENABLE_ACCELERATED_2D_CANVAS = ;
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING = $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING_$(WK_COCOA_TOUCH));
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING_cocoatouch = ENABLE_ACCELERATED_OVERFLOW_SCROLLING;
> 
>+ENABLE_CSSOM_OVERSCROLL_BEHAVIOR = ENABLE_CSSOM_OVERSCROLL_BEHAVIOR;
>+
> ENABLE_APPLE_PAY = $(ENABLE_APPLE_PAY_$(WK_PLATFORM_NAME));
> ENABLE_APPLE_PAY_iphoneos = ENABLE_APPLE_PAY;
> ENABLE_APPLE_PAY_iphonesimulator = ENABLE_APPLE_PAY;
>@@ -374,4 +376,4 @@ ENABLE_WIRELESS_PLAYBACK_TARGET = ENABLE_WIRELESS_PLAYBACK_TARGET;
> 
> ENABLE_XSLT = ENABLE_XSLT;
> 
>-FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>+FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_CSSOM_OVERSCROLL_BEHAVIOR) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>diff --git a/Source/WebCore/css/CSSComputedStyleDeclaration.cpp b/Source/WebCore/css/CSSComputedStyleDeclaration.cpp
>index db9c6d79e08..6e3744450b0 100644
>--- a/Source/WebCore/css/CSSComputedStyleDeclaration.cpp
>+++ b/Source/WebCore/css/CSSComputedStyleDeclaration.cpp
>@@ -195,6 +195,10 @@ static const CSSPropertyID computedProperties[] = {
>     CSSPropertyOutlineWidth,
>     CSSPropertyOverflowWrap,
>     CSSPropertyOverflowX,
>+#if ENABLE(CSSOM_OVERSCROLL_BEHAVIOR)
>+    CSSPropertyOverscrollBehaviorX,
>+    CSSPropertyOverscrollBehaviorY,
>+#endif
>     CSSPropertyOverflowY,
>     CSSPropertyPaddingBottom,
>     CSSPropertyPaddingLeft,
>@@ -3277,6 +3281,14 @@ RefPtr<CSSValue> ComputedStyleExtractor::valueForPropertyinStyle(const RenderSty
>             return cssValuePool.createValue(style.overflowX());
>         case CSSPropertyOverflowY:
>             return cssValuePool.createValue(style.overflowY());
>+#if ENABLE(CSSOM_OVERSCROLL_BEHAVIOR)
>+        case CSSPropertyOverscrollBehavior:
>+            return cssValuePool.createValue(std::max(style.overscrollBehaviorX(), style.overscrollBehaviorY()));
>+        case CSSPropertyOverscrollBehaviorX:
>+            return cssValuePool.createValue(style.overscrollBehaviorX());
>+        case CSSPropertyOverscrollBehaviorY:
>+            return cssValuePool.createValue(style.overscrollBehaviorY());
>+#endif
>         case CSSPropertyPaddingTop:
>             return zoomAdjustedPaddingOrMarginPixelValue<&RenderStyle::paddingTop, &RenderBoxModelObject::computedCSSPaddingTop>(style, renderer);
>         case CSSPropertyPaddingRight:
>diff --git a/Source/WebCore/css/CSSPrimitiveValueMappings.h b/Source/WebCore/css/CSSPrimitiveValueMappings.h
>index 5ee6f638603..0b9ac0b69d2 100644
>--- a/Source/WebCore/css/CSSPrimitiveValueMappings.h
>+++ b/Source/WebCore/css/CSSPrimitiveValueMappings.h
>@@ -2208,6 +2208,44 @@ template<> inline CSSPrimitiveValue::operator Overflow() const
>     return Overflow::Visible;
> }
> 
>+#if ENABLE(CSSOM_OVERSCROLL_BEHAVIOR)
>+template<> inline CSSPrimitiveValue::CSSPrimitiveValue(OverscrollBehavior e)
>+    : CSSValue(PrimitiveClass)
>+{
>+    m_primitiveUnitType = CSS_VALUE_ID;
>+    switch (e) {
>+    case OverscrollBehavior::Contain:
>+        m_value.valueID = CSSValueContain;
>+        break;
>+    case OverscrollBehavior::None:
>+        m_value.valueID = CSSValueNone;
>+        break;
>+    case OverscrollBehavior::Auto:
>+        m_value.valueID = CSSValueAuto;
>+        break;
>+    }
>+}
>+
>+template<> inline CSSPrimitiveValue::operator OverscrollBehavior() const
>+{
>+    ASSERT(isValueID());
>+
>+    switch (m_value.valueID) {
>+    case CSSValueContain:
>+        return OverscrollBehavior::Contain;
>+    case CSSValueNone:
>+        return OverscrollBehavior::None;
>+    case CSSValueAuto:
>+        return OverscrollBehavior::Auto;
>+    default:
>+        break;
>+    }
>+
>+    ASSERT_NOT_REACHED();
>+    return OverscrollBehavior::Auto;
>+}
>+#endif
>+
> template<> inline CSSPrimitiveValue::CSSPrimitiveValue(BreakBetween e)
>     : CSSValue(PrimitiveClass)
> {
>diff --git a/Source/WebCore/css/CSSProperties.json b/Source/WebCore/css/CSSProperties.json
>index 537dd70e58b..10bef70bb3d 100644
>--- a/Source/WebCore/css/CSSProperties.json
>+++ b/Source/WebCore/css/CSSProperties.json
>@@ -3055,6 +3055,44 @@
>                 "url": "https://www.w3.org/TR/css-overflow-3/#propdef-overflow-y"
>             }
>         },
>+        "overscroll-behavior": {
>+            "codegen-properties": {
>+                "enable-if": "ENABLE_CSSOM_OVERSCROLL_BEHAVIOR",
>+                "longhands": [
>+                    "overscroll-behavior-x",
>+                    "overscroll-behavior-y"
>+                ]
>+            },
>+            "specification": {
>+                "url": "https://wicg.github.io/overscroll-behavior/#propdef-overscroll-behavior"
>+            }
>+        },
>+        "overscroll-behavior-x": {
>+            "codegen-properties": {
>+                "enable-if": "ENABLE_CSSOM_OVERSCROLL_BEHAVIOR"
>+            },
>+            "values": [
>+                "contain",
>+                "none",
>+                "auto"
>+            ],
>+            "specification": {
>+                "url": "https://wicg.github.io/overscroll-behavior/#propdef-overscroll-behavior-x"
>+            }
>+        },
>+        "overscroll-behavior-y": {
>+            "codegen-properties": {
>+                "enable-if": "ENABLE_CSSOM_OVERSCROLL_BEHAVIOR"
>+            },
>+            "values": [
>+                "contain",
>+                "none",
>+                "auto"
>+            ],
>+            "specification": {
>+                "url": "https://wicg.github.io/overscroll-behavior/#propdef-overscroll-behavior-y"
>+            }
>+        },
>         "padding": {
>             "codegen-properties": {
>                 "longhands": [
>diff --git a/Source/WebCore/css/CSSValueKeywords.in b/Source/WebCore/css/CSSValueKeywords.in
>index c71c74fcb5c..a52a9a50edb 100644
>--- a/Source/WebCore/css/CSSValueKeywords.in
>+++ b/Source/WebCore/css/CSSValueKeywords.in
>@@ -1356,6 +1356,11 @@ scroll-position
> manipulation
> #endif
> 
>+#if defined(ENABLE_CSSOM_OVERSCROLL_BEHAVIOR) && ENABLE_CSSOM_OVERSCROLL_BEHAVIOR
>+// overscroll-behavior
>+// contain
>+#endif
>+
> // hanging-punctuation
> allow-end
> first
>diff --git a/Source/WebCore/css/parser/CSSParserFastPaths.cpp b/Source/WebCore/css/parser/CSSParserFastPaths.cpp
>index 54595d84e3e..34773f7953d 100644
>--- a/Source/WebCore/css/parser/CSSParserFastPaths.cpp
>+++ b/Source/WebCore/css/parser/CSSParserFastPaths.cpp
>@@ -608,6 +608,11 @@ bool CSSParserFastPaths::isValidKeywordPropertyAndValue(CSSPropertyID propertyId
>         return valueID == CSSValueVisible || valueID == CSSValueHidden || valueID == CSSValueScroll || valueID == CSSValueAuto || valueID == CSSValueOverlay;
>     case CSSPropertyOverflowY: // visible | hidden | scroll | auto | overlay | -webkit-paged-x | -webkit-paged-y
>         return valueID == CSSValueVisible || valueID == CSSValueHidden || valueID == CSSValueScroll || valueID == CSSValueAuto || valueID == CSSValueOverlay || valueID == CSSValueWebkitPagedX || valueID == CSSValueWebkitPagedY;
>+#if ENABLE(CSSOM_OVERSCROLL_BEHAVIOR)
>+    case CSSPropertyOverscrollBehaviorX:
>+    case CSSPropertyOverscrollBehaviorY:
>+        return valueID == CSSValueContain || valueID == CSSValueNone || valueID == CSSValueAuto;
>+#endif
>     case CSSPropertyBreakAfter:
>     case CSSPropertyBreakBefore:
>         return valueID == CSSValueAuto || valueID == CSSValueAvoid || valueID == CSSValueAvoidPage || valueID == CSSValuePage || valueID == CSSValueLeft || valueID == CSSValueRight || valueID == CSSValueRecto || valueID == CSSValueVerso || valueID == CSSValueAvoidColumn || valueID == CSSValueColumn;
>@@ -851,6 +856,10 @@ bool CSSParserFastPaths::isKeywordPropertyID(CSSPropertyID propertyId)
>     case CSSPropertyOverflowWrap:
>     case CSSPropertyOverflowX:
>     case CSSPropertyOverflowY:
>+#if ENABLE(CSSOM_OVERSCROLL_BEHAVIOR)
>+    case CSSPropertyOverscrollBehaviorX:
>+    case CSSPropertyOverscrollBehaviorY:
>+#endif
>     case CSSPropertyPointerEvents:
>     case CSSPropertyPosition:
>     case CSSPropertyResize:
>diff --git a/Source/WebCore/rendering/style/RenderStyle.h b/Source/WebCore/rendering/style/RenderStyle.h
>index a208500f07b..fb1fad221b4 100644
>--- a/Source/WebCore/rendering/style/RenderStyle.h
>+++ b/Source/WebCore/rendering/style/RenderStyle.h
>@@ -332,6 +332,11 @@ public:
>     Overflow overflowInlineDirection() const { return isHorizontalWritingMode() ? overflowX() : overflowY(); }
>     Overflow overflowBlockDirection() const { return isHorizontalWritingMode() ? overflowY() : overflowX(); }
>     bool isOverflowVisible() const { return overflowX() == Overflow::Visible || overflowY() == Overflow::Visible; }
>+
>+#if ENABLE(CSSOM_OVERSCROLL_BEHAVIOR)
>+    OverscrollBehavior overscrollBehaviorX() const { return static_cast<OverscrollBehavior>(m_rareNonInheritedData->overscrollBehaviorX); }
>+    OverscrollBehavior overscrollBehaviorY() const { return static_cast<OverscrollBehavior>(m_rareNonInheritedData->overscrollBehaviorY); }
>+#endif
>     
>     Visibility visibility() const { return static_cast<Visibility>(m_inheritedFlags.visibility); }
>     VerticalAlign verticalAlign() const { return static_cast<VerticalAlign>(m_nonInheritedFlags.verticalAlign); }
>@@ -882,6 +887,10 @@ public:
> 
>     void setOverflowX(Overflow v) { m_nonInheritedFlags.overflowX =  static_cast<unsigned>(v); }
>     void setOverflowY(Overflow v) { m_nonInheritedFlags.overflowY = static_cast<unsigned>(v); }
>+#if ENABLE(CSSOM_OVERSCROLL_BEHAVIOR)
>+    void setOverscrollBehaviorX(OverscrollBehavior v) { SET_VAR(m_rareNonInheritedData, overscrollBehaviorX, static_cast<unsigned>(v)); }
>+    void setOverscrollBehaviorY(OverscrollBehavior v) { SET_VAR(m_rareNonInheritedData, overscrollBehaviorY, static_cast<unsigned>(v)); }
>+#endif
>     void setVisibility(Visibility v) { m_inheritedFlags.visibility = static_cast<unsigned>(v); }
>     void setVerticalAlign(VerticalAlign v) { m_nonInheritedFlags.verticalAlign = static_cast<unsigned>(v); }
>     void setVerticalAlignLength(Length&& length) { setVerticalAlign(VerticalAlign::Length); SET_VAR(m_boxData, m_verticalAlign, WTFMove(length)); }
>@@ -1425,6 +1434,10 @@ public:
>     // Initial values for all the properties
>     static Overflow initialOverflowX() { return Overflow::Visible; }
>     static Overflow initialOverflowY() { return Overflow::Visible; }
>+#if ENABLE(CSSOM_OVERSCROLL_BEHAVIOR)
>+    static OverscrollBehavior initialOverscrollBehaviorX() { return OverscrollBehavior::Auto; }
>+    static OverscrollBehavior initialOverscrollBehaviorY() { return OverscrollBehavior::Auto; }
>+#endif
>     static Clear initialClear() { return Clear::None; }
>     static DisplayType initialDisplay() { return DisplayType::Inline; }
>     static EUnicodeBidi initialUnicodeBidi() { return UBNormal; }
>diff --git a/Source/WebCore/rendering/style/RenderStyleConstants.h b/Source/WebCore/rendering/style/RenderStyleConstants.h
>index 283df645907..866f2eaf8e1 100644
>--- a/Source/WebCore/rendering/style/RenderStyleConstants.h
>+++ b/Source/WebCore/rendering/style/RenderStyleConstants.h
>@@ -261,6 +261,14 @@ enum class Overflow : uint8_t {
>     PagedY
> };
> 
>+#if ENABLE(CSSOM_OVERSCROLL_BEHAVIOR)
>+enum class OverscrollBehavior : uint8_t {
>+    Contain,
>+    None,
>+    Auto
>+};
>+#endif
>+
> enum class VerticalAlign : uint8_t {
>     Baseline,
>     Middle,
>diff --git a/Source/WebCore/rendering/style/StyleRareNonInheritedData.cpp b/Source/WebCore/rendering/style/StyleRareNonInheritedData.cpp
>index 0aeac9750c6..9b547db4e1e 100644
>--- a/Source/WebCore/rendering/style/StyleRareNonInheritedData.cpp
>+++ b/Source/WebCore/rendering/style/StyleRareNonInheritedData.cpp
>@@ -59,6 +59,10 @@ StyleRareNonInheritedData::StyleRareNonInheritedData()
> #if ENABLE(CSS_SCROLL_SNAP)
>     , scrollSnapPort(StyleScrollSnapPort::create())
>     , scrollSnapArea(StyleScrollSnapArea::create())
>+#endif
>+#if ENABLE(CSSOM_OVERSCROLL_BEHAVIOR)
>+    , overscrollBehaviorX(static_cast<unsigned>(RenderStyle::initialOverscrollBehaviorX()))
>+    , overscrollBehaviorY(static_cast<unsigned>(RenderStyle::initialOverscrollBehaviorY()))
> #endif
>     , willChange(RenderStyle::initialWillChange())
>     , mask(FillLayerType::Mask)
>@@ -135,6 +139,10 @@ inline StyleRareNonInheritedData::StyleRareNonInheritedData(const StyleRareNonIn
> #if ENABLE(CSS_SCROLL_SNAP)
>     , scrollSnapPort(o.scrollSnapPort)
>     , scrollSnapArea(o.scrollSnapArea)
>+#endif
>+#if ENABLE(CSSOM_OVERSCROLL_BEHAVIOR)
>+    , overscrollBehaviorX(o.overscrollBehaviorX)
>+    , overscrollBehaviorY(o.overscrollBehaviorY)
> #endif
>     , content(o.content ? o.content->clone() : nullptr)
>     , counterDirectives(o.counterDirectives ? std::make_unique<CounterDirectiveMap>(*o.counterDirectives) : nullptr)
>@@ -236,6 +244,10 @@ bool StyleRareNonInheritedData::operator==(const StyleRareNonInheritedData& o) c
> #if ENABLE(CSS_SCROLL_SNAP)
>         && scrollSnapPort == o.scrollSnapPort
>         && scrollSnapArea == o.scrollSnapArea
>+#endif
>+#if ENABLE(CSSOM_OVERSCROLL_BEHAVIOR)
>+        && overscrollBehaviorX == o.overscrollBehaviorX
>+        && overscrollBehaviorY == o.overscrollBehaviorY
> #endif
>         && contentDataEquivalent(o)
>         && arePointingToEqualData(counterDirectives, o.counterDirectives)
>diff --git a/Source/WebCore/rendering/style/StyleRareNonInheritedData.h b/Source/WebCore/rendering/style/StyleRareNonInheritedData.h
>index 089ccfa438c..26043d9bc08 100644
>--- a/Source/WebCore/rendering/style/StyleRareNonInheritedData.h
>+++ b/Source/WebCore/rendering/style/StyleRareNonInheritedData.h
>@@ -128,6 +128,11 @@ public:
>     DataRef<StyleScrollSnapArea> scrollSnapArea;
> #endif
> 
>+#if ENABLE(CSSOM_OVERSCROLL_BEHAVIOR)
>+    unsigned overscrollBehaviorX : 2; // OverscrollBehavior
>+    unsigned overscrollBehaviorY : 2; // OverscrollBehavior
>+#endif
>+
>     std::unique_ptr<ContentData> content;
>     std::unique_ptr<CounterDirectiveMap> counterDirectives;
>     String altText;
>diff --git a/Source/WebKit/Configurations/FeatureDefines.xcconfig b/Source/WebKit/Configurations/FeatureDefines.xcconfig
>index dfa4a259773..e71d666aab4 100644
>--- a/Source/WebKit/Configurations/FeatureDefines.xcconfig
>+++ b/Source/WebKit/Configurations/FeatureDefines.xcconfig
>@@ -40,6 +40,8 @@ ENABLE_ACCELERATED_2D_CANVAS = ;
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING = $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING_$(WK_COCOA_TOUCH));
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING_cocoatouch = ENABLE_ACCELERATED_OVERFLOW_SCROLLING;
> 
>+ENABLE_CSSOM_OVERSCROLL_BEHAVIOR = ENABLE_CSSOM_OVERSCROLL_BEHAVIOR;
>+
> ENABLE_APPLE_PAY = $(ENABLE_APPLE_PAY_$(WK_PLATFORM_NAME));
> ENABLE_APPLE_PAY_iphoneos = ENABLE_APPLE_PAY;
> ENABLE_APPLE_PAY_iphonesimulator = ENABLE_APPLE_PAY;
>@@ -374,4 +376,4 @@ ENABLE_WIRELESS_PLAYBACK_TARGET = ENABLE_WIRELESS_PLAYBACK_TARGET;
> 
> ENABLE_XSLT = ENABLE_XSLT;
> 
>-FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>+FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_CSSOM_OVERSCROLL_BEHAVIOR) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>diff --git a/Source/WebKitLegacy/mac/Configurations/FeatureDefines.xcconfig b/Source/WebKitLegacy/mac/Configurations/FeatureDefines.xcconfig
>index dfa4a259773..e71d666aab4 100644
>--- a/Source/WebKitLegacy/mac/Configurations/FeatureDefines.xcconfig
>+++ b/Source/WebKitLegacy/mac/Configurations/FeatureDefines.xcconfig
>@@ -40,6 +40,8 @@ ENABLE_ACCELERATED_2D_CANVAS = ;
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING = $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING_$(WK_COCOA_TOUCH));
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING_cocoatouch = ENABLE_ACCELERATED_OVERFLOW_SCROLLING;
> 
>+ENABLE_CSSOM_OVERSCROLL_BEHAVIOR = ENABLE_CSSOM_OVERSCROLL_BEHAVIOR;
>+
> ENABLE_APPLE_PAY = $(ENABLE_APPLE_PAY_$(WK_PLATFORM_NAME));
> ENABLE_APPLE_PAY_iphoneos = ENABLE_APPLE_PAY;
> ENABLE_APPLE_PAY_iphonesimulator = ENABLE_APPLE_PAY;
>@@ -374,4 +376,4 @@ ENABLE_WIRELESS_PLAYBACK_TARGET = ENABLE_WIRELESS_PLAYBACK_TARGET;
> 
> ENABLE_XSLT = ENABLE_XSLT;
> 
>-FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>+FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_CSSOM_OVERSCROLL_BEHAVIOR) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>diff --git a/Source/cmake/WebKitFeatures.cmake b/Source/cmake/WebKitFeatures.cmake
>index 116e0d96974..67af6edd59b 100644
>--- a/Source/cmake/WebKitFeatures.cmake
>+++ b/Source/cmake/WebKitFeatures.cmake
>@@ -162,6 +162,7 @@ macro(WEBKIT_OPTION_BEGIN)
>     WEBKIT_OPTION_DEFINE(ENABLE_SERVICE_CONTROLS "Toggle service controls support" PRIVATE OFF)
>     WEBKIT_OPTION_DEFINE(ENABLE_SERVICE_WORKER "Toggle ServiceWorker support" PRIVATE OFF)
>     WEBKIT_OPTION_DEFINE(ENABLE_SMOOTH_SCROLLING "Toggle smooth scrolling" PRIVATE ON)
>+    WEBKIT_OPTION_DEFINE(ENABLE_CSSOM_OVERSCROLL_BEHAVIOR "Toggle CSSOM overscroll behavior support" PRIVATE ON)
>     WEBKIT_OPTION_DEFINE(ENABLE_SPEECH_SYNTHESIS "Toggle Speech Synthesis API support" PRIVATE OFF)
>     WEBKIT_OPTION_DEFINE(ENABLE_SPELLCHECK "Toggle Spellchecking support (requires Enchant)" PRIVATE OFF)
>     WEBKIT_OPTION_DEFINE(ENABLE_STREAMS_API "Toggle Streams API support" PRIVATE ON)
>diff --git a/Source/cmake/tools/vsprops/FeatureDefines.props b/Source/cmake/tools/vsprops/FeatureDefines.props
>index 4d42faa9b55..e5ab36bbfc9 100644
>--- a/Source/cmake/tools/vsprops/FeatureDefines.props
>+++ b/Source/cmake/tools/vsprops/FeatureDefines.props
>@@ -4,6 +4,7 @@
>     <ENABLE_3D_TRANSFORMS>ENABLE_3D_TRANSFORMS</ENABLE_3D_TRANSFORMS>
>     <ENABLE_ACCELERATED_2D_CANVAS />
>     <ENABLE_ACCELERATED_OVERFLOW_SCROLLING />
>+    <ENABLE_CSSOM_OVERSCROLL_BEHAVIOR>ENABLE_CSSOM_OVERSCROLL_BEHAVIOR</ENABLE_CSSOM_OVERSCROLL_BEHAVIOR>
>     <ENABLE_ATTACHMENT_ELEMENT>ENABLE_ATTACHMENT_ELEMENT</ENABLE_ATTACHMENT_ELEMENT>
>     <ENABLE_CHANNEL_MESSAGING>ENABLE_CHANNEL_MESSAGING</ENABLE_CHANNEL_MESSAGING>
>     <ENABLE_CSS3_CONDITIONAL_RULES>ENABLE_CSS3_CONDITIONAL_RULES</ENABLE_CSS3_CONDITIONAL_RULES>
>@@ -76,7 +77,7 @@
>   </PropertyGroup>
>   <ItemDefinitionGroup>
>     <ClCompile>
>-      <PreprocessorDefinitions>$(ENABLE_3D_TRANSFORMS);$(ENABLE_ACCELERATED_2D_CANVAS);$(ENABLE_ACCELERATED_OVERFLOW_SCROLLING);$(ENABLE_ATTACHMENT_ELEMENT);$(ENABLE_CHANNEL_MESSAGING);$(ENABLE_CSS3_CONDITIONAL_RULES);$(ENABLE_CSS_IMAGE_SET);$(ENABLE_CSS3_TEXT);$(ENABLE_CSS_BOX_DECORATION_BREAK);$(ENABLE_CSS_SHADERS);$(ENABLE_CSS_COMPOSITING);$(ENABLE_CSS_SELECTORS_LEVEL4);$(ENABLE_CSS_SHAPE_INSIDE);$(ENABLE_CSS_TRANSFORMS_ANIMATIONS_TRANSITIONS_UNPREFIXED);$(ENABLE_CURSOR_VISIBILITY);$(ENABLE_CUSTOM_SCHEME_HANDLER);$(ENABLE_DATAGRID);$(ENABLE_DATALIST_ELEMENT);$(ENABLE_DEVICE_ORIENTATION);$(ENABLE_DIRECTORY_UPLOAD);$(ENABLE_ENCRYPTED_MEDIA);$(ENABLE_FETCH_API);$(ENABLE_FILE_SYSTEM);$(ENABLE_FULLSCREEN_API);$(ENABLE_GAMEPAD);$(ENABLE_GEOLOCATION);$(ENABLE_HIGH_DPI_CANVAS);$(ENABLE_ICONDATABASE);$(ENABLE_INDEXED_DATABASE);$(ENABLE_INPUT_TYPE_COLOR);$(ENABLE_INPUT_SPEECH);$(ENABLE_INPUT_TYPE_DATE);$(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE);$(ENABLE_INPUT_TYPE_DATETIMELOCAL);$(ENABLE_INPUT_TYPE_MONTH);$(ENABLE_INPUT_TYPE_TIME);$(ENABLE_INPUT_TYPE_WEEK);$(ENABLE_INTL);$(ENABLE_LEGACY_CSS_VENDOR_PREFIXES);$(ENABLE_LEGACY_ENCRYPTED_MEDIA);$(ENABLE_LINK_PRERENDER);$(ENABLE_MATHML);$(ENABLE_METER_ELEMENT);$(ENABLE_MICRODATA);$(ENABLE_MOUSE_CURSOR_SCALE);$(ENABLE_NOTIFICATIONS);$(ENABLE_QUOTA);$(ENABLE_NAVIGATOR_CONTENT_UTILS);$(ENABLE_STREAMS_API);$(ENABLE_SCRIPTED_SPEECH);$(ENABLE_SHARED_WORKERS);$(ENABLE_MEDIA_CONTROLS_SCRIPT);$(ENABLE_MEDIA_SOURCE);$(ENABLE_MEDIA_STATISTICS);$(ENABLE_SQL_DATABASE);$(ENABLE_STYLE_SCOPED);$(ENABLE_SUBPIXEL_LAYOUT);$(ENABLE_SVG_DOM_OBJC_BINDINGS);$(ENABLE_SVG_FONTS);$(ENABLE_VIDEO);$(ENABLE_VIDEO_TRACK);$(ENABLE_WEB_AUDIO);$(ENABLE_WEBGL);$(ENABLE_WEBGPU);$(ENABLE_WEBVTT_REGIONS);$(ENABLE_XHR_TIMEOUT);$(ENABLE_XSLT);%(PreprocessorDefinitions)</PreprocessorDefinitions>
>+      <PreprocessorDefinitions>$(ENABLE_3D_TRANSFORMS);$(ENABLE_ACCELERATED_2D_CANVAS);$(ENABLE_ACCELERATED_OVERFLOW_SCROLLING);$(ENABLE_CSSOM_OVERSCROLL_BEHAVIOR);$(ENABLE_ATTACHMENT_ELEMENT);$(ENABLE_CHANNEL_MESSAGING);$(ENABLE_CSS3_CONDITIONAL_RULES);$(ENABLE_CSS_IMAGE_SET);$(ENABLE_CSS3_TEXT);$(ENABLE_CSS_BOX_DECORATION_BREAK);$(ENABLE_CSS_SHADERS);$(ENABLE_CSS_COMPOSITING);$(ENABLE_CSS_SELECTORS_LEVEL4);$(ENABLE_CSS_SHAPE_INSIDE);$(ENABLE_CSS_TRANSFORMS_ANIMATIONS_TRANSITIONS_UNPREFIXED);$(ENABLE_CURSOR_VISIBILITY);$(ENABLE_CUSTOM_SCHEME_HANDLER);$(ENABLE_DATAGRID);$(ENABLE_DATALIST_ELEMENT);$(ENABLE_DEVICE_ORIENTATION);$(ENABLE_DIRECTORY_UPLOAD);$(ENABLE_ENCRYPTED_MEDIA);$(ENABLE_FETCH_API);$(ENABLE_FILE_SYSTEM);$(ENABLE_FULLSCREEN_API);$(ENABLE_GAMEPAD);$(ENABLE_GEOLOCATION);$(ENABLE_HIGH_DPI_CANVAS);$(ENABLE_ICONDATABASE);$(ENABLE_INDEXED_DATABASE);$(ENABLE_INPUT_TYPE_COLOR);$(ENABLE_INPUT_SPEECH);$(ENABLE_INPUT_TYPE_DATE);$(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE);$(ENABLE_INPUT_TYPE_DATETIMELOCAL);$(ENABLE_INPUT_TYPE_MONTH);$(ENABLE_INPUT_TYPE_TIME);$(ENABLE_INPUT_TYPE_WEEK);$(ENABLE_INTL);$(ENABLE_LEGACY_CSS_VENDOR_PREFIXES);$(ENABLE_LEGACY_ENCRYPTED_MEDIA);$(ENABLE_LINK_PRERENDER);$(ENABLE_MATHML);$(ENABLE_METER_ELEMENT);$(ENABLE_MICRODATA);$(ENABLE_MOUSE_CURSOR_SCALE);$(ENABLE_NOTIFICATIONS);$(ENABLE_QUOTA);$(ENABLE_NAVIGATOR_CONTENT_UTILS);$(ENABLE_STREAMS_API);$(ENABLE_SCRIPTED_SPEECH);$(ENABLE_SHARED_WORKERS);$(ENABLE_MEDIA_CONTROLS_SCRIPT);$(ENABLE_MEDIA_SOURCE);$(ENABLE_MEDIA_STATISTICS);$(ENABLE_SQL_DATABASE);$(ENABLE_STYLE_SCOPED);$(ENABLE_SUBPIXEL_LAYOUT);$(ENABLE_SVG_DOM_OBJC_BINDINGS);$(ENABLE_SVG_FONTS);$(ENABLE_VIDEO);$(ENABLE_VIDEO_TRACK);$(ENABLE_WEB_AUDIO);$(ENABLE_WEBGL);$(ENABLE_WEBGPU);$(ENABLE_WEBVTT_REGIONS);$(ENABLE_XHR_TIMEOUT);$(ENABLE_XSLT);%(PreprocessorDefinitions)</PreprocessorDefinitions>
>     </ClCompile>
>   </ItemDefinitionGroup>
>   <ItemGroup>
>@@ -92,6 +93,10 @@
>       <Value>$(ENABLE_ACCELERATED_OVERFLOW_SCROLLING)</Value>
>       <EnvironmentVariable>true</EnvironmentVariable>
>     </BuildMacro>
>+    <BuildMacro Include="ENABLE_CSSOM_OVERSCROLL_BEHAVIOR">
>+      <Value>$(ENABLE_CSSOM_OVERSCROLL_BEHAVIOR)</Value>
>+      <EnvironmentVariable>true</EnvironmentVariable>
>+    </BuildMacro>
>     <BuildMacro Include="ENABLE_ATTACHMENT_ELEMENT">
>       <Value>$(ENABLE_ATTACHMENT_ELEMENT)</Value>
>       <EnvironmentVariable>true</EnvironmentVariable>
>diff --git a/Source/cmake/tools/vsprops/FeatureDefinesCairo.props b/Source/cmake/tools/vsprops/FeatureDefinesCairo.props
>index 113aade5c8f..f2e91c136a1 100644
>--- a/Source/cmake/tools/vsprops/FeatureDefinesCairo.props
>+++ b/Source/cmake/tools/vsprops/FeatureDefinesCairo.props
>@@ -4,6 +4,7 @@
>     <ENABLE_3D_TRANSFORMS>ENABLE_3D_TRANSFORMS</ENABLE_3D_TRANSFORMS>
>     <ENABLE_ACCELERATED_2D_CANVAS />
>     <ENABLE_ACCELERATED_OVERFLOW_SCROLLING />
>+    <ENABLE_CSSOM_OVERSCROLL_BEHAVIOR>ENABLE_CSSOM_OVERSCROLL_BEHAVIOR</ENABLE_CSSOM_OVERSCROLL_BEHAVIOR>
>     <ENABLE_ATTACHMENT_ELEMENT>ENABLE_ATTACHMENT_ELEMENT</ENABLE_ATTACHMENT_ELEMENT>
>     <ENABLE_CHANNEL_MESSAGING>ENABLE_CHANNEL_MESSAGING</ENABLE_CHANNEL_MESSAGING>
>     <ENABLE_CSS3_CONDITIONAL_RULES>ENABLE_CSS3_CONDITIONAL_RULES</ENABLE_CSS3_CONDITIONAL_RULES>
>@@ -75,7 +76,7 @@
>   </PropertyGroup>
>   <ItemDefinitionGroup>
>     <ClCompile>
>-      <PreprocessorDefinitions>$(ENABLE_3D_TRANSFORMS);$(ENABLE_ACCELERATED_2D_CANVAS);$(ENABLE_ACCELERATED_OVERFLOW_SCROLLING);$(ENABLE_ATTACHMENT_ELEMENT);$(ENABLE_CHANNEL_MESSAGING);$(ENABLE_CSS3_CONDITIONAL_RULES);$(ENABLE_CSS_IMAGE_SET);$(ENABLE_CSS3_TEXT);$(ENABLE_CSS_BOX_DECORATION_BREAK);$(ENABLE_CSS_SHADERS);$(ENABLE_CSS_COMPOSITING);$(ENABLE_CSS_SELECTORS_LEVEL4);$(ENABLE_CSS_SHAPE_INSIDE);$(ENABLE_CSS_TRANSFORMS_ANIMATIONS_TRANSITIONS_UNPREFIXED);$(ENABLE_CURSOR_VISIBILITY);$(ENABLE_CUSTOM_SCHEME_HANDLER);$(ENABLE_DATAGRID);$(ENABLE_DATALIST_ELEMENT);$(ENABLE_DEVICE_ORIENTATION);$(ENABLE_DIRECTORY_UPLOAD);$(ENABLE_ENCRYPTED_MEDIA);$(ENABLE_FETCH_API);$(ENABLE_FILE_SYSTEM);$(ENABLE_FULLSCREEN_API);$(ENABLE_GAMEPAD);$(ENABLE_GEOLOCATION);$(ENABLE_HIGH_DPI_CANVAS);$(ENABLE_ICONDATABASE);$(ENABLE_INDEXED_DATABASE);$(ENABLE_INPUT_TYPE_COLOR);$(ENABLE_INPUT_SPEECH);$(ENABLE_INPUT_TYPE_DATE);$(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE);$(ENABLE_INPUT_TYPE_DATETIMELOCAL);$(ENABLE_INPUT_TYPE_MONTH);$(ENABLE_INPUT_TYPE_TIME);$(ENABLE_INPUT_TYPE_WEEK);$(ENABLE_INTL);$(ENABLE_LEGACY_CSS_VENDOR_PREFIXES);$(ENABLE_LEGACY_ENCRYPTED_MEDIA);$(ENABLE_LINK_PRERENDER);$(ENABLE_MATHML);$(ENABLE_METER_ELEMENT);$(ENABLE_MICRODATA);$(ENABLE_MOUSE_CURSOR_SCALE);$(ENABLE_NOTIFICATIONS);$(ENABLE_QUOTA);$(ENABLE_NAVIGATOR_CONTENT_UTILS);$(ENABLE_SCRIPTED_SPEECH);$(ENABLE_SHARED_WORKERS);$(ENABLE_MEDIA_CONTROLS_SCRIPT);$(ENABLE_MEDIA_SOURCE);$(ENABLE_MEDIA_STATISTICS);$(ENABLE_SQL_DATABASE);$(ENABLE_STYLE_SCOPED);$(ENABLE_SUBPIXEL_LAYOUT);$(ENABLE_SVG_DOM_OBJC_BINDINGS);$(ENABLE_SVG_FONTS);$(ENABLE_VIDEO);$(ENABLE_VIDEO_TRACK);$(ENABLE_WEB_AUDIO);$(ENABLE_WEBGL);$(ENABLE_WEBVTT_REGIONS);$(ENABLE_XHR_TIMEOUT);$(ENABLE_XSLT);%(PreprocessorDefinitions)</PreprocessorDefinitions>
>+      <PreprocessorDefinitions>$(ENABLE_3D_TRANSFORMS);$(ENABLE_ACCELERATED_2D_CANVAS);$(ENABLE_ACCELERATED_OVERFLOW_SCROLLING);$(ENABLE_CSSOM_OVERSCROLL_BEHAVIOR);$(ENABLE_ATTACHMENT_ELEMENT);$(ENABLE_CHANNEL_MESSAGING);$(ENABLE_CSS3_CONDITIONAL_RULES);$(ENABLE_CSS_IMAGE_SET);$(ENABLE_CSS3_TEXT);$(ENABLE_CSS_BOX_DECORATION_BREAK);$(ENABLE_CSS_SHADERS);$(ENABLE_CSS_COMPOSITING);$(ENABLE_CSS_SELECTORS_LEVEL4);$(ENABLE_CSS_SHAPE_INSIDE);$(ENABLE_CSS_TRANSFORMS_ANIMATIONS_TRANSITIONS_UNPREFIXED);$(ENABLE_CURSOR_VISIBILITY);$(ENABLE_CUSTOM_SCHEME_HANDLER);$(ENABLE_DATAGRID);$(ENABLE_DATALIST_ELEMENT);$(ENABLE_DEVICE_ORIENTATION);$(ENABLE_DIRECTORY_UPLOAD);$(ENABLE_ENCRYPTED_MEDIA);$(ENABLE_FETCH_API);$(ENABLE_FILE_SYSTEM);$(ENABLE_FULLSCREEN_API);$(ENABLE_GAMEPAD);$(ENABLE_GEOLOCATION);$(ENABLE_HIGH_DPI_CANVAS);$(ENABLE_ICONDATABASE);$(ENABLE_INDEXED_DATABASE);$(ENABLE_INPUT_TYPE_COLOR);$(ENABLE_INPUT_SPEECH);$(ENABLE_INPUT_TYPE_DATE);$(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE);$(ENABLE_INPUT_TYPE_DATETIMELOCAL);$(ENABLE_INPUT_TYPE_MONTH);$(ENABLE_INPUT_TYPE_TIME);$(ENABLE_INPUT_TYPE_WEEK);$(ENABLE_INTL);$(ENABLE_LEGACY_CSS_VENDOR_PREFIXES);$(ENABLE_LEGACY_ENCRYPTED_MEDIA);$(ENABLE_LINK_PRERENDER);$(ENABLE_MATHML);$(ENABLE_METER_ELEMENT);$(ENABLE_MICRODATA);$(ENABLE_MOUSE_CURSOR_SCALE);$(ENABLE_NOTIFICATIONS);$(ENABLE_QUOTA);$(ENABLE_NAVIGATOR_CONTENT_UTILS);$(ENABLE_SCRIPTED_SPEECH);$(ENABLE_SHARED_WORKERS);$(ENABLE_MEDIA_CONTROLS_SCRIPT);$(ENABLE_MEDIA_SOURCE);$(ENABLE_MEDIA_STATISTICS);$(ENABLE_SQL_DATABASE);$(ENABLE_STYLE_SCOPED);$(ENABLE_SUBPIXEL_LAYOUT);$(ENABLE_SVG_DOM_OBJC_BINDINGS);$(ENABLE_SVG_FONTS);$(ENABLE_VIDEO);$(ENABLE_VIDEO_TRACK);$(ENABLE_WEB_AUDIO);$(ENABLE_WEBGL);$(ENABLE_WEBVTT_REGIONS);$(ENABLE_XHR_TIMEOUT);$(ENABLE_XSLT);%(PreprocessorDefinitions)</PreprocessorDefinitions>
>     </ClCompile>
>   </ItemDefinitionGroup>
>   <ItemGroup>
>@@ -91,6 +92,10 @@
>       <Value>$(ENABLE_ACCELERATED_OVERFLOW_SCROLLING)</Value>
>       <EnvironmentVariable>true</EnvironmentVariable>
>     </BuildMacro>
>+    <BuildMacro Include="ENABLE_CSSOM_OVERSCROLL_BEHAVIOR">
>+      <Value>$(ENABLE_CSSOM_OVERSCROLL_BEHAVIOR)</Value>
>+      <EnvironmentVariable>true</EnvironmentVariable>
>+    </BuildMacro>
>     <BuildMacro Include="ENABLE_ATTACHMENT_ELEMENT">
>       <Value>$(ENABLE_ATTACHMENT_ELEMENT)</Value>
>       <EnvironmentVariable>true</EnvironmentVariable>
>diff --git a/Tools/Scripts/webkitperl/FeatureList.pm b/Tools/Scripts/webkitperl/FeatureList.pm
>index 6c9060d020d..967908a6384 100644
>--- a/Tools/Scripts/webkitperl/FeatureList.pm
>+++ b/Tools/Scripts/webkitperl/FeatureList.pm
>@@ -118,6 +118,7 @@ my (
>     $resolutionMediaQuerySupport,
>     $scriptedSpeechSupport,
>     $serviceWorkerSupport,
>+    $cssomOverscrollBehaviorSupport,
>     $subtleCrypto,
>     $svgFontsSupport,
>     $systemMallocSupport,
>@@ -337,6 +338,9 @@ my @features = (
>     { option => "service-worker", desc => "Toggle Service Worker support",
>       define => "ENABLE_SERVICE_WORKER", value => \$serviceWorkerSupport },
> 
>+    { option => "cssom-overscroll-behavior", desc => "Toggle CSSOM Overscroll Behavior",
>+      define => "ENABLE_CSSOM_OVERSCROLL_BEHAVIOR", value => \$cssomOverscrollBehaviorSupport },
>+
>     { option => "subtle-crypto", desc => "Toggle WebCrypto Subtle-Crypto support",
>       define => "ENABLE_SUBTLE_CRYPTO", value => \$subtleCrypto },
> 
>diff --git a/Tools/TestWebKitAPI/Configurations/FeatureDefines.xcconfig b/Tools/TestWebKitAPI/Configurations/FeatureDefines.xcconfig
>index dfa4a259773..e71d666aab4 100644
>--- a/Tools/TestWebKitAPI/Configurations/FeatureDefines.xcconfig
>+++ b/Tools/TestWebKitAPI/Configurations/FeatureDefines.xcconfig
>@@ -40,6 +40,8 @@ ENABLE_ACCELERATED_2D_CANVAS = ;
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING = $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING_$(WK_COCOA_TOUCH));
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING_cocoatouch = ENABLE_ACCELERATED_OVERFLOW_SCROLLING;
> 
>+ENABLE_CSSOM_OVERSCROLL_BEHAVIOR = ENABLE_CSSOM_OVERSCROLL_BEHAVIOR;
>+
> ENABLE_APPLE_PAY = $(ENABLE_APPLE_PAY_$(WK_PLATFORM_NAME));
> ENABLE_APPLE_PAY_iphoneos = ENABLE_APPLE_PAY;
> ENABLE_APPLE_PAY_iphonesimulator = ENABLE_APPLE_PAY;
>@@ -374,4 +376,4 @@ ENABLE_WIRELESS_PLAYBACK_TARGET = ENABLE_WIRELESS_PLAYBACK_TARGET;
> 
> ENABLE_XSLT = ENABLE_XSLT;
> 
>-FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>+FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_CSSOM_OVERSCROLL_BEHAVIOR) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>-- 
>2.18.0
>

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