Make PointerEvent coordinates fractional for touch

third_party/WebKit/Source/core/events/MouseRelatedEvent.h

Index: third_party/WebKit/Source/core/events/MouseRelatedEvent.h
diff --git a/third_party/WebKit/Source/core/events/MouseRelatedEvent.h b/third_party/WebKit/Source/core/events/MouseRelatedEvent.h
index 6d90d75eaf845aba5b91e226656c5d2798e6d6e9..ac3d2cf5847780f931f3bcafd0b53fb4299d68ae 100644
--- a/third_party/WebKit/Source/core/events/MouseRelatedEvent.h
+++ b/third_party/WebKit/Source/core/events/MouseRelatedEvent.h
@@ -43,14 +43,24 @@ class CORE_EXPORT MouseRelatedEvent : public UIEventWithKeyState {
   };
   // Note that these values are adjusted to counter the effects of zoom, so that
   // values exposed via DOM APIs are invariant under zooming.
-  int screenX() const { return m_screenLocation.x(); }
-  int screenY() const { return m_screenLocation.y(); }
-  const IntPoint& screenLocation() const { return m_screenLocation; }
-  int clientX() const { return m_clientLocation.x().toInt(); }
-  int clientY() const { return m_clientLocation.y().toInt(); }
+  double screenX() const {
+    return isPointerEvent() ? m_screenLocation.x().toDouble()

[Rick Byers, 2016/10/12 14:09:54]

It seems odd that this pattern of conditional return values is necessary.  Can't
you just initialize the event in the first place to truncate to integers for
mouse events but not for pointer events?

[mustaq, 2016/10/12 16:00:01]

The problem here is that the initialization is done at MouseRelatedEvent
constructors where the vtable for the actual subclass being constructed (e.g.
MouseEvent or PointerEvent) is not "ready". As a result, all isXyzEvent()
functions return false.

+                            : m_screenLocation.x().toInt();
+  }
+  double screenY() const {
+    return isPointerEvent() ? m_screenLocation.y().toDouble()
+                            : m_screenLocation.y().toInt();
+  }
+  double clientX() const {
+    return isPointerEvent() ? m_clientLocation.x().toDouble()
+                            : m_clientLocation.x().toInt();
+  }
+  double clientY() const {
+    return isPointerEvent() ? m_clientLocation.y().toDouble()
+                            : m_clientLocation.y().toInt();
+  }
   int movementX() const { return m_movementDelta.x().toInt(); }
   int movementY() const { return m_movementDelta.y().toInt(); }
-  const LayoutPoint& clientLocation() const { return m_clientLocation; }
   int layerX();
   int layerY();
   int offsetX();
@@ -90,14 +100,14 @@ class CORE_EXPORT MouseRelatedEvent : public UIEventWithKeyState {
   MouseRelatedEvent(const AtomicString& type,
                     const MouseEventInit& initializer);
 
-  void initCoordinates(const LayoutPoint& clientLocation);
+  void initCoordinates(const double clientX, const double clientY);
   void receivedTarget() final;
 
   void computePageLocation();
   void computeRelativePosition();
 
   // Expose these so MouseEvent::initMouseEvent can set them.
-  IntPoint m_screenLocation;
+  LayoutPoint m_screenLocation;
   LayoutPoint m_clientLocation;
   LayoutPoint m_movementDelta;