Compute effective touch action in StyleAdjuster.

third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc.
  * All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
@@ skipping 17 matching lines @@
  * Boston, MA 02110-1301, USA.
  */
 
 #include "core/css/resolver/StyleAdjuster.h"
 
 #include "core/HTMLNames.h"
 #include "core/SVGNames.h"
 #include "core/dom/ContainerNode.h"
 #include "core/dom/Document.h"
 #include "core/dom/Element.h"
+#include "core/dom/NodeComputedStyle.h"
+#include "core/dom/StyleChangeReason.h"
 #include "core/frame/LocalFrameView.h"
 #include "core/frame/Settings.h"
 #include "core/frame/UseCounter.h"
 #include "core/html/HTMLIFrameElement.h"
 #include "core/html/HTMLImageElement.h"
 #include "core/html/HTMLInputElement.h"
 #include "core/html/HTMLPlugInElement.h"
 #include "core/html/HTMLTableCellElement.h"
 #include "core/html/HTMLTextAreaElement.h"
+#include "core/layout/LayoutObject.h"
 #include "core/layout/LayoutTheme.h"
 #include "core/style/ComputedStyle.h"
 #include "core/style/ComputedStyleConstants.h"
 #include "core/svg/SVGSVGElement.h"
 #include "platform/Length.h"
 #include "platform/transforms/TransformOperations.h"
 #include "platform/wtf/Assertions.h"
 
 namespace blink {
 
@@ skipping 304 matching lines @@
       UseCounter::Count(document,
                         WebFeature::kFlexboxPercentagePaddingVertical);
     }
     if (style.MarginBefore().IsPercentOrCalc() ||
         style.MarginAfter().IsPercentOrCalc()) {
       UseCounter::Count(document, WebFeature::kFlexboxPercentageMarginVertical);
     }
   }
 }
 
+static void AdjustEffectiveTouchAction(ComputedStyle& style,
+                                       const ComputedStyle& parent_style,
+                                       Element* element) {
+  TouchAction action = parent_style.GetEffectiveTouchAction();
+
+  bool is_svg_root = element && element->IsSVGElement() &&
+                     isSVGSVGElement(*element) && element->parentNode() &&
+                     !element->parentNode()->IsSVGElement();
+  bool is_non_replaced_inline_elements =
+      style.IsDisplayInlineType() &&
+      !(style.IsDisplayReplacedType() || is_svg_root ||
+        isHTMLImageElement(element));
+  bool is_table_row_or_column = style.IsDisplayTableRowOrColumnType();
+
+  // According to W3C specs, touch actions are only supported by elements that
+  // support both the CSS width and height properties.
+  // See https://www.w3.org/TR/pointerevents/#the-touch-action-css-property.
+  if (is_non_replaced_inline_elements || is_table_row_or_column) {
+    style.SetEffectiveTouchAction(action);
+    return;
+  }
+
+  // The effective touch action is the intersection of the touch-action values
+  // of the current element and all of its ancestors up to the one that
+  // implements the gesture. Since panning is implemented by the scroller it is
+  // re-enabled for scrolling elements.
+  // The panning-restricted cancellation should also apply to iframes, so we
+  // allow (panning & local touch action) on the first descendant element of a
+  // iframe element.
+  bool is_child_document =
+      element && element == element->GetDocument().documentElement() &&
+      element->GetDocument().LocalOwner();
+
+  if (is_child_document) {
+    const ComputedStyle* frame_style =
+        element->GetDocument().LocalOwner()->GetComputedStyle();
+    if (frame_style)

[flackr, 2017/06/21 15:24:34]

Is it possible for frame_style to be null? This is coming from an "ancestor"
element so it should already have computed style shouldn't it?

[sunxd, 2017/06/22 17:22:55]

In many webkit_unit_tests, e.g. PrintContextFrameTest.WithScrolledSubframe,
computing child's properties can trigger a nullptr here. I think the reason is
that a lot of the tests do not call UpdateAllLifecyclePhases. I don't know
whether we should fix this (add a TODO now and fix it with a new patch, as there
are too many test failures) or we add a guarding if-condition here.

+      action = frame_style->GetEffectiveTouchAction();
+  }
+
+  if (style.ScrollsOverflow() || is_child_document)
+    action |= TouchAction::kTouchActionPan;
+
+  // Apply the adjusted parent effective touch actions.
+  style.SetEffectiveTouchAction(style.GetTouchAction() & action);
+
+  if (element && element->IsFrameOwnerElement() &&
+      ToHTMLFrameOwnerElement(element)->contentDocument()) {
+    Element* content_document_element =
+        ToHTMLFrameOwnerElement(element)->contentDocument()->documentElement();
+    if (content_document_element) {
+      content_document_element->SetNeedsStyleRecalc(
+          kSubtreeStyleChange,
+          StyleChangeReasonForTracing::Create(
+              StyleChangeReason::kInheritedStyleChangeFromParentFrame));
+    }
+  }
+}
+
 void StyleAdjuster::AdjustComputedStyle(
     ComputedStyle& style,
     const ComputedStyle& parent_style,
     const ComputedStyle& layout_parent_style,
     Element* element) {
   if (style.Display() != EDisplay::kNone) {
     if (element && element->IsHTMLElement())
       AdjustStyleForHTMLElement(style, ToHTMLElement(*element));
 
     // Per the spec, position 'static' and 'relative' in the top layer compute
@@ skipping 110 matching lines @@
   if (style.GetPosition() == EPosition::kSticky)
     style.SetSubtreeIsSticky(true);
 
   // If the inherited value of justify-items includes the 'legacy' keyword,
   // 'auto' computes to the the inherited value.  Otherwise, 'auto' computes to
   // 'normal'.
   if (style.JustifyItemsPosition() == kItemPositionAuto) {
     if (parent_style.JustifyItemsPositionType() == kLegacyPosition)
       style.SetJustifyItems(parent_style.JustifyItems());
   }
+
+  AdjustEffectiveTouchAction(style, parent_style, element);
 }
-
 }  // namespace blink