SnapManager implementation using V8 Extras - {WIP}

third_party/WebKit/Source/core/page/scrolling/SnapCoordinator.cpp

 // Copyright 2016 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 "SnapCoordinator.h"
 
 #include "core/dom/Element.h"
 #include "core/dom/Node.h"
 #include "core/dom/NodeComputedStyle.h"
 #include "core/layout/LayoutBlock.h"
 #include "core/layout/LayoutBox.h"
 #include "core/layout/LayoutView.h"
 #include "core/style/ComputedStyle.h"
 #include "platform/LengthFunctions.h"
 
 namespace blink {
 
-SnapCoordinator::SnapCoordinator()
-    : m_snapContainers()
+SnapCoordinator* SnapCoordinator::create(Client* client)
+{
+    return new SnapCoordinator(client);
+}
+
+SnapCoordinator::SnapCoordinator(Client* client)
+    : m_client(client)
 {
 }
 
 SnapCoordinator::~SnapCoordinator() { }
 
-SnapCoordinator* SnapCoordinator::create()
-{
-    return new SnapCoordinator();
-}
-
 // Returns the scroll container that can be affected by this snap area.
 static LayoutBox* findSnapContainer(const LayoutBox& snapArea)
 {
     // According to the new spec https://drafts.csswg.org/css-scroll-snap/#snap-model
     // "Snap positions must only affect the nearest ancestor (on the element’s
     // containing block chain) scroll container".
     Element* viewportDefiningElement = snapArea.node()->document().viewportDefiningElement();
     LayoutBox* box = snapArea.containingBlock();
     while (box && !box->hasOverflowClip() && !box->isLayoutView() && box->node() != viewportDefiningElement)
         box = box->containingBlock();
@@ skipping 100 matching lines @@
             }
         }
     }
 
     if (didAddSnapAreaOffset)
         std::sort(result.begin(), result.end());
 
     return result;
 }
 
+
+
+void SnapCoordinator::notifyLayoutUpdated()
+{
+    // TODO(majidvp): This should be replaced with compositor worker precommit
+    for (const LayoutBox* container : m_snapContainers) {
+        ContainerNode& containerNode =  toContainerNode(*container->node());
+        SnapOffsets newOffsets;
+        newOffsets.horizontal = snapOffsets(containerNode, HorizontalScrollbar);
+        newOffsets.vertical = snapOffsets(containerNode, VerticalScrollbar);
+
+        // report only if it is different from the cached value
+        if (m_offsetMap.contains(container) && m_offsetMap.get(container) == newOffsets)
+            continue;
+        m_offsetMap.set(container, newOffsets);
+        if (m_client)
+            m_client->didUpdateSnapOffsets(*container, newOffsets);
+    }
+}
+
+
 #ifndef NDEBUG
 
 void SnapCoordinator::showSnapAreaMap()
 {
     for (auto& container : m_snapContainers)
         showSnapAreasFor(container);
 }
 
 void SnapCoordinator::showSnapAreasFor(const LayoutBox* container)
 {
     const char* prefix = "    ";
     container->node()->showNode();
     if (SnapAreaSet* snapAreas = container->snapAreas()) {
         for (auto& snapArea : *snapAreas) {
             snapArea->node()->showNode(prefix);
         }
     }
 }
 
 #endif
 
+bool operator==(const SnapOffsets& a, const SnapOffsets& b)
+{
+    return a.horizontal == b.horizontal && a.vertical == b.vertical;
+}
+
 } // namespace blink