Compute snap offsets according to CSS Scroll Snap Spec Level 1

third_party/WebKit/Source/core/dom/Document.cpp

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index f05f277465d432d8b9a6bc5a7f928ba1b961aeee..5c1f0aa6a81e27e8dab5a4f13959aa809e79dd84 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -194,6 +194,7 @@
 #include "core/page/PointerLockController.h"
 #include "core/page/scrolling/RootScroller.h"
 #include "core/page/scrolling/ScrollingCoordinator.h"
+#include "core/page/scrolling/SnapCoordinator.h"
 #include "core/svg/SVGDocumentExtensions.h"
 #include "core/svg/SVGScriptElement.h"
 #include "core/svg/SVGTitleElement.h"
@@ -1625,6 +1626,9 @@ void Document::inheritHtmlAndBodyElementStyles(StyleRecalcChange change)
         columnGap = overflowStyle->columnGap();
     }
 
+    ScrollSnapType snapType = overflowStyle->getScrollSnapType();
+    const LengthPoint& snapDestination = overflowStyle->scrollSnapDestination();
+
     RefPtr<ComputedStyle> documentStyle = layoutView()->mutableStyle();
     if (documentStyle->getWritingMode() != rootWritingMode
         || documentStyle->direction() != rootDirection
@@ -1633,7 +1637,9 @@ void Document::inheritHtmlAndBodyElementStyles(StyleRecalcChange change)
         || documentStyle->imageRendering() != imageRendering
         || documentStyle->overflowX() != overflowX
         || documentStyle->overflowY() != overflowY
-        || documentStyle->columnGap() != columnGap) {
+        || documentStyle->columnGap() != columnGap
+        || documentStyle->getScrollSnapType() != snapType
+        || documentStyle->scrollSnapDestination() != snapDestination) {
         RefPtr<ComputedStyle> newStyle = ComputedStyle::clone(*documentStyle);
         newStyle->setWritingMode(rootWritingMode);
         newStyle->setDirection(rootDirection);
@@ -1643,6 +1649,8 @@ void Document::inheritHtmlAndBodyElementStyles(StyleRecalcChange change)
         newStyle->setOverflowX(overflowX);
         newStyle->setOverflowY(overflowY);
         newStyle->setColumnGap(columnGap);
+        newStyle->setScrollSnapType(snapType);
+        newStyle->setScrollSnapDestination(snapDestination);
         layoutView()->setStyle(newStyle);
         setupFontBuilder(*newStyle);
     }
@@ -5520,6 +5528,14 @@ bool Document::threadedParsingEnabledForTesting()
     return s_threadedParsingEnabledForTesting;
 }
 
+SnapCoordinator* Document::snapCoordinator()
+{
+    if (RuntimeEnabledFeatures::cssScrollSnapPointsEnabled() && !m_snapCoordinator)
+        m_snapCoordinator = SnapCoordinator::create();
+
+    return m_snapCoordinator.get();
+}
+
 void Document::setContextFeatures(ContextFeatures& features)
 {
     m_contextFeatures = &features;
@@ -5960,6 +5976,7 @@ DEFINE_TRACE(Document)
     visitor->trace(m_canvasFontCache);
     visitor->trace(m_intersectionObserverController);
     visitor->trace(m_intersectionObserverData);
+    visitor->trace(m_snapCoordinator);
     Supplementable<Document>::trace(visitor);
     TreeScope::trace(visitor);
     ContainerNode::trace(visitor);