Implement CSS: scroll-boundary-behavior

third_party/WebKit/Source/core/input/ScrollManager.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 "core/input/ScrollManager.h"
 
 #include <memory>
 #include "core/dom/DOMNodeIds.h"
+#include "core/dom/NodeComputedStyle.h"
 #include "core/events/GestureEvent.h"
 #include "core/frame/BrowserControls.h"
 #include "core/frame/FrameView.h"
 #include "core/html/HTMLFrameOwnerElement.h"
 #include "core/input/EventHandler.h"
 #include "core/input/EventHandlingUtil.h"
 #include "core/layout/LayoutBlock.h"
 #include "core/layout/LayoutPart.h"
 #include "core/layout/api/LayoutViewItem.h"
 #include "core/loader/DocumentLoader.h"
@@ skipping 53 matching lines @@
          GetAutoscrollController()->MiddleClickAutoscrollInProgress();
 }
 
 AutoscrollController* ScrollManager::GetAutoscrollController() const {
   if (Page* page = frame_->GetPage())
     return &page->GetAutoscrollController();
   return nullptr;
 }
 
 void ScrollManager::RecomputeScrollChain(const Node& start_node,
+                                         const ScrollState& scroll_state,
                                          std::deque<int>& scroll_chain) {
   scroll_chain.clear();
 
   DCHECK(start_node.GetLayoutObject());
   LayoutBox* cur_box = start_node.GetLayoutObject()->EnclosingBox();
   Element* document_element = frame_->GetDocument()->documentElement();
+  bool x_dominated =
+      (std::abs(scroll_state.deltaX()) > std::abs(scroll_state.deltaY()));
 
   // Scrolling propagates along the containing block chain and ends at the
   // RootScroller element. The RootScroller element will have a custom
   // applyScroll callback that scrolls the frame or element.
   while (cur_box) {
     Node* cur_node = cur_box->GetNode();
     Element* cur_element = nullptr;
 
     // FIXME: this should reject more elements, as part of crbug.com/410974.
     if (cur_node && cur_node->IsElementNode()) {
       cur_element = ToElement(cur_node);
     } else if (cur_node && cur_node->IsDocumentNode()) {
       // In normal circumastances, the documentElement will be the root
       // scroller but the documentElement itself isn't a containing block,
       // that'll be the document node rather than the element.
       cur_element = document_element;
     }
 
     if (cur_element) {
       scroll_chain.push_front(DOMNodeIds::IdForNode(cur_element));
       if (IsViewportScrollingElement(*cur_element) ||
           cur_element == document_element)
         break;
+
+      if ((x_dominated &&
+           cur_element->GetComputedStyle()->ScrollBoundaryBehaviorX() !=
+               EScrollBoundaryBehavior::kAuto) ||
+          (!x_dominated &&
+           cur_element->GetComputedStyle()->ScrollBoundaryBehaviorY() !=
+               EScrollBoundaryBehavior::kAuto))
+        break;
     }
 
     cur_box = cur_box->ContainingBlock();
   }
 }
 
 bool ScrollManager::LogicalScroll(ScrollDirection direction,
                                   ScrollGranularity granularity,
                                   Node* start_node,
                                   Node* mouse_press_node) {
@@ skipping 60 matching lines @@
 void ScrollManager::SetFrameWasScrolledByUser() {
   if (DocumentLoader* document_loader = frame_->Loader().GetDocumentLoader())
     document_loader->GetInitialScrollState().was_scrolled_by_user = true;
 }
 
 void ScrollManager::CustomizedScroll(const Node& start_node,
                                      ScrollState& scroll_state) {
   if (scroll_state.FullyConsumed())
     return;
 
-  if (scroll_state.deltaX() || scroll_state.deltaY())
+  if (scroll_state.deltaX() || scroll_state.deltaY()) {
     frame_->GetDocument()->UpdateStyleAndLayoutIgnorePendingStylesheets();
+    if (current_scroll_chain_.empty())
+      RecomputeScrollChain(start_node, scroll_state, current_scroll_chain_);
+    scroll_state.SetScrollChain(current_scroll_chain_);
 
-  if (current_scroll_chain_.empty())
-    RecomputeScrollChain(start_node, current_scroll_chain_);
-  scroll_state.SetScrollChain(current_scroll_chain_);
-
-  scroll_state.distributeToScrollChainDescendant();
+    scroll_state.distributeToScrollChainDescendant();
+  }
 }
 
 void ScrollManager::ComputeScrollRelatedMetrics(
     uint32_t* non_composited_main_thread_scrolling_reasons,
     int* scroller_size) {
   // When scrolling on the main thread, the scrollableArea may or may not be
   // composited. Either way, we have recorded either the reasons stored in
   // its layer or the reason NonFastScrollableRegion from the compositor
   // side. Here we record scrolls that occurred on main thread due to a
   // non-composited scroller.
@@ skipping 445 matching lines @@
                                 &should_update_capture)) {
       if (should_update_capture)
         scrollbar_handling_scroll_gesture_ = scrollbar;
       return true;
     }
   }
   return false;
 }
 
 }  // namespace blink