Add scrollbar width style to ScrollableAreaParameters

https://bugs.webkit.org/show_bug.cgi?id=259017

Reviewed by Simon Fraser.

This patch adds scrollbarWidthStyle to ScrollableAreaParameters.
This is wired up to ScrollerPairMac to replace the hardcoded ScrollbarWidth::Auto.
This will allow a follow up to fix the thin value having no affect with composited scrolling.

This patch has no behaviour changes.

* Source/WebCore/page/scrolling/AsyncScrollingCoordinator.cpp:
(WebCore::AsyncScrollingCoordinator::setScrollingNodeScrollableAreaGeometry):
* Source/WebCore/page/scrolling/ScrollingCoordinatorTypes.h:
(WebCore::ScrollableAreaParameters::operator== const):
* Source/WebCore/page/scrolling/ScrollingTreeScrollingNode.h:
* Source/WebCore/page/scrolling/mac/ScrollerPairMac.mm:
(WebCore::ScrollerPairMac::scrollbarWidthStyle const):
* Source/WebCore/platform/ScrollTypes.h:
* Source/WebKit/Shared/WebCoreArgumentCoders.serialization.in:

Canonical link: https://commits.webkit.org/265907@main

Source/WebCore/page/scrolling/AsyncScrollingCoordinator.cpp

@@ -946,6 +946,7 @@ void AsyncScrollingCoordinator::setScrollingNodeScrollableAreaGeometry(Scrolling
     scrollParameters.horizontalNativeScrollbarVisibility = scrollableArea.horizontalNativeScrollbarVisibility();
     scrollParameters.verticalNativeScrollbarVisibility = scrollableArea.verticalNativeScrollbarVisibility();
     scrollParameters.useDarkAppearanceForScrollbars = scrollableArea.useDarkAppearanceForScrollbars();
+    scrollParameters.scrollbarWidthStyle = scrollableArea.scrollbarWidthStyle();
 
     scrollingNode->setScrollableAreaParameters(scrollParameters);
 

Source/WebCore/page/scrolling/ScrollingCoordinatorTypes.h

@@ -89,6 +89,8 @@ struct ScrollableAreaParameters {
 
     bool useDarkAppearanceForScrollbars { false };
 
+    ScrollbarWidth scrollbarWidthStyle { ScrollbarWidth::Auto };
+
     bool operator==(const ScrollableAreaParameters& other) const
     {
         return horizontalScrollElasticity == other.horizontalScrollElasticity
@@ -101,7 +103,8 @@ struct ScrollableAreaParameters {
             && allowsVerticalScrolling == other.allowsVerticalScrolling
             && horizontalNativeScrollbarVisibility == other.horizontalNativeScrollbarVisibility
             && verticalNativeScrollbarVisibility == other.verticalNativeScrollbarVisibility
-            && useDarkAppearanceForScrollbars == other.useDarkAppearanceForScrollbars;
+            && useDarkAppearanceForScrollbars == other.useDarkAppearanceForScrollbars
+            && scrollbarWidthStyle == other.scrollbarWidthStyle;
     }
 };
 

Source/WebCore/page/scrolling/ScrollingTreeScrollingNode.h

@@ -130,7 +130,9 @@ class WEBCORE_EXPORT ScrollingTreeScrollingNode : public ScrollingTreeNode {
 
     OverscrollBehavior horizontalOverscrollBehavior() const { return m_scrollableAreaParameters.horizontalOverscrollBehavior; }
     OverscrollBehavior verticalOverscrollBehavior() const { return m_scrollableAreaParameters.verticalOverscrollBehavior; }
-
+
+    ScrollbarWidth scrollbarWidthStyle() const { return m_scrollableAreaParameters.scrollbarWidthStyle; }
+
     virtual String scrollbarStateForOrientation(ScrollbarOrientation) const { return ""_s; }
 
     void scrollbarVisibilityDidChange(ScrollbarOrientation, bool);

Source/WebCore/page/scrolling/mac/ScrollerPairMac.mm

@@ -262,8 +262,7 @@ - (void)scrollerImpPair:(NSScrollerImpPair *)scrollerImpPair updateScrollerStyle
 
 ScrollbarWidth ScrollerPairMac::scrollbarWidthStyle() const
 {
-    // FIXME: This should be based on the element style. See <https://webkit.org/b/257430>
-    return ScrollbarWidth::Auto;
+    return m_scrollingNode.scrollbarWidthStyle();
 }
 
 ScrollerPairMac::Values ScrollerPairMac::valuesForOrientation(ScrollbarOrientation orientation)

Source/WebCore/platform/ScrollTypes.h

@@ -422,4 +422,13 @@ template<> struct EnumTraits<WebCore::ScrollbarOrientation> {
         WebCore::ScrollbarOrientation::Vertical
     >;
 };
+
+template<> struct EnumTraits<WebCore::ScrollbarWidth> {
+    using values = EnumValues<
+        WebCore::ScrollbarWidth,
+        WebCore::ScrollbarWidth::Auto,
+        WebCore::ScrollbarWidth::Thin,
+        WebCore::ScrollbarWidth::None
+    >;
+};
 } // namespace WTF

Source/WebKit/Shared/WebCoreArgumentCoders.serialization.in

@@ -1980,6 +1980,13 @@ header: <WebCore/ScrollTypes.h>
     ReplacedByCustomScrollbar
 };
 
+header: <WebCore/ScrollTypes.h>
+[CustomHeader] enum class WebCore::ScrollbarWidth : uint8_t {
+    Auto,
+    Thin,
+    None
+};
+
 header: <WebCore/ScrollingCoordinatorTypes.h>
 [CustomHeader] struct WebCore::ScrollableAreaParameters {
     WebCore::ScrollElasticity horizontalScrollElasticity;
@@ -1993,6 +2000,7 @@ header: <WebCore/ScrollingCoordinatorTypes.h>
     WebCore::NativeScrollbarVisibility horizontalNativeScrollbarVisibility;
     WebCore::NativeScrollbarVisibility verticalNativeScrollbarVisibility;
     bool useDarkAppearanceForScrollbars;
+    WebCore::ScrollbarWidth scrollbarWidthStyle;
 };
 
 header: <WebCore/ScrollingCoordinatorTypes.h>