Compute effective touch action in StyleAdjuster.

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

Index: third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp
diff --git a/third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp b/third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp
index d561f3f6cb0dcfc2b8bc7f28686600aa54c3415c..77c9018c0cfc6f8f78e8d85f57822850ffea6e1f 100644
--- a/third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp
+++ b/third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp
@@ -35,6 +35,8 @@
 #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"
@@ -44,6 +46,7 @@
 #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"
@@ -368,6 +371,63 @@ static void AdjustStyleForDisplay(ComputedStyle& style,
   }
 }
 
+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.
+  if (style.ScrollsOverflow())
+    action |= TouchAction::kTouchActionPan;
+
+  // 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.
+  if (element && element == element->GetDocument().documentElement() &&
+      element->GetDocument().LocalOwner()) {
+    const ComputedStyle* frame_style =
+        element->GetDocument().LocalOwner()->GetComputedStyle();
+    if (frame_style) {
+      action =
+          frame_style->GetEffectiveTouchAction() | TouchAction::kTouchActionPan;

[flackr, 2017/06/19 15:45:42]

I still think it'd be cleaner to re-enable kTouchActionPan as the same for
scrollsoverflow and subframes. I.e. something like this:

bool is_child_document = element && element->GetDocument().documentElement() &&
element->GetDocument().LocalOwner()

if (is_child_document)
  action = frame_style->GetEffectiveTouchAction();

if (style.scrollsOverflow() || is_child_document)
  action |= kTouchActionPan

[sunxd, 2017/06/21 15:13:03]

Done.

+    }
+  }
+
+  // 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::kStyleSheetChange));

[flackr, 2017/06/19 15:45:42]

kStyleSheetChange is not the correct reason to set here. We should probably add
a reason, maybe something like "InheritedStyleFromParentFrame"?

[sunxd, 2017/06/21 15:13:03]

Done.

+    }
+  }
+}
+
 void StyleAdjuster::AdjustComputedStyle(
     ComputedStyle& style,
     const ComputedStyle& parent_style,
@@ -498,6 +558,7 @@ void StyleAdjuster::AdjustComputedStyle(
     if (parent_style.JustifyItemsPositionType() == kLegacyPosition)
       style.SetJustifyItems(parent_style.JustifyItems());
   }
-}
 
+  AdjustEffectiveTouchAction(style, parent_style, element);
+}
 }  // namespace blink