Compute effective touch action in StyleAdjuster.

third_party/WebKit/Source/core/input/TouchActionUtil.cpp

 // Copyright 2015 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/TouchActionUtil.h"
 
 #include "core/dom/Node.h"
+#include "core/dom/NodeComputedStyle.h"
 #include "core/html/HTMLFrameOwnerElement.h"
 #include "core/layout/LayoutBox.h"
 #include "core/layout/LayoutObject.h"
 
 namespace blink {
 namespace TouchActionUtil {
 
-namespace {
-
-// touch-action applies to all elements with both width AND height properties.
-// According to the CSS Box Model Spec
-// (http://dev.w3.org/csswg/css-box/#the-width-and-height-properties)
-// width applies to all elements but non-replaced inline elements, table rows,
-// and row groups and height applies to all elements but non-replaced inline
-// elements, table columns, and column groups.
-bool SupportsTouchAction(const LayoutObject& object) {
-  if (object.IsInline() && !object.IsAtomicInlineLevel())
-    return false;
-  if (object.IsTableRow() || object.IsLayoutTableCol())
-    return false;
-
-  return true;
-}
-
-const Node* ParentNodeAcrossFrames(const Node* cur_node) {
-  Node* parent_node = FlatTreeTraversal::Parent(*cur_node);
-  if (parent_node)
-    return parent_node;
-
-  if (cur_node->IsDocumentNode()) {
-    const Document* doc = ToDocument(cur_node);
-    return doc->LocalOwner();
-  }
-
-  return nullptr;
-}
-
-}  // namespace
-
 TouchAction ComputeEffectiveTouchAction(const Node& node) {
-  // Start by permitting all actions, then walk the elements supporting
-  // touch-action from the target node up to root document, exclude any
-  // prohibited actions at or below the element that supports them.
-  // I.e. pan-related actions are considered up to the nearest scroller,
-  // and zoom related actions are considered up to the root.
-  TouchAction effective_touch_action = TouchAction::kTouchActionAuto;
-  TouchAction handled_touch_actions = TouchAction::kTouchActionNone;
-  for (const Node* cur_node = &node; cur_node;
-       cur_node = ParentNodeAcrossFrames(cur_node)) {
-    if (LayoutObject* layout_object = cur_node->GetLayoutObject()) {
-      if (SupportsTouchAction(*layout_object)) {
-        TouchAction action = layout_object->Style()->GetTouchAction();
-        action |= handled_touch_actions;
-        effective_touch_action &= action;
-        if (effective_touch_action == TouchAction::kTouchActionNone)
-          break;
-      }
-
-      // If we've reached an ancestor that supports panning, stop allowing
-      // panning to be disabled.
-      if ((layout_object->IsBox() &&
-           ToLayoutBox(layout_object)->ScrollsOverflow()) ||
-          layout_object->IsLayoutView())
-        handled_touch_actions |= TouchAction::kTouchActionPan;
-    }
-  }
-  return effective_touch_action;
+  return node.GetComputedStyle()

[flackr, 2017/06/29 14:34:06]

Do some nodes have a null ComputedStyle? Maybe we still need to walk to the
nearest node which has a ComputedStyle.

[sunxd, 2017/06/29 15:21:19]

Done.

+             ? node.GetComputedStyle()->GetEffectiveTouchAction()
+             : TouchAction::kTouchActionAuto;
 }
 
 }  // namespace TouchActionUtil
 }  // namespace blink