Make PointerEvent coordinates fractional for touch

third_party/WebKit/Source/core/events/MouseEvent.idl

 /*
  * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 // https://w3c.github.io/uievents/#interface-MouseEvent
 
 [
     Constructor(DOMString type, optional MouseEventInit eventInitDict),
     ConstructorCallWith=ScriptState,
 ] interface MouseEvent : UIEvent {
-    readonly attribute long             screenX;
-    readonly attribute long             screenY;
-    readonly attribute long             clientX;
-    readonly attribute long             clientY;
+    readonly attribute double           screenX;
+    readonly attribute double           screenY;
+    readonly attribute double           clientX;
+    readonly attribute double           clientY;
     readonly attribute boolean          ctrlKey;
     readonly attribute boolean          shiftKey;
     readonly attribute boolean          altKey;
     readonly attribute boolean          metaKey;
     readonly attribute short            button;
     readonly attribute unsigned short   buttons;
     readonly attribute EventTarget?     relatedTarget;
     boolean getModifierState(DOMString keyArg);
 
     // https://w3c.github.io/uievents/#idl-interface-MouseEvent-initializers
     // TODO(foolip): None of the initMouseEvent() arguments should be optional.
     [CallWith=ScriptState, Measure] void initMouseEvent([Default=Undefined] optional DOMString type,
                                                         [Default=Undefined] optional boolean bubbles,
                                                         [Default=Undefined] optional boolean cancelable,
                                                         [Default=Undefined] optional Window? view,
                                                         [Default=Undefined] optional long detail,
                                                         [Default=Undefined] optional long screenX,
                                                         [Default=Undefined] optional long screenY,
                                                         [Default=Undefined] optional long clientX,
                                                         [Default=Undefined] optional long clientY,
                                                         [Default=Undefined] optional boolean ctrlKey,
                                                         [Default=Undefined] optional boolean altKey,
                                                         [Default=Undefined] optional boolean shiftKey,
                                                         [Default=Undefined] optional boolean metaKey,
                                                         [Default=Undefined] optional unsigned short button,
                                                         [Default=Undefined] optional EventTarget? relatedTarget);
 
     // CSSOM View Module
     // http://dev.w3.org/csswg/cssom-view/#extensions-to-the-mouseevent-interface
-    // TODO(foolip): These attributes should be of type double, and the spec
-    // also redefines screenX/Y and clientX/Y as double.
+    // TODO(foolip): These attributes should be of type double.
     readonly attribute long pageX;
     readonly attribute long pageY;

[Rick Byers, 2016/10/13 19:08:21]

the Touch page* co-ordinates are double today, so we should upgrade those as
well here.

Maybe just do them all?  It seems weird to change some of the co-ordinates and
not others.  If there's a good reason to delay the ones below though (i.e. if it
complicates the CL much) then I'm OK doing them separately.

[mustaq, 2016/10/14 14:26:58]

Let's do them separately, to minimize MouseEvent related risks.

     [MeasureAs=MouseEventX] readonly attribute long x;
     [MeasureAs=MouseEventY] readonly attribute long y;
     [MeasureAs=MouseEventOffsetX] readonly attribute long offsetX;
     [MeasureAs=MouseEventOffsetY] readonly attribute long offsetY;
 
     // Pointer Lock
     // https://dvcs.w3.org/hg/pointerlock/raw-file/default/index.html#extensions-to-the-mouseevent-interface
     [MeasureAs=MouseEventMovementX] readonly attribute long movementX;
     [MeasureAs=MouseEventMovementY] readonly attribute long movementY;
 
     // Canvas Hit Regions
     // https://html.spec.whatwg.org/multipage/scripting.html#MouseEvent-partial
     [RuntimeEnabled=ExperimentalCanvasFeatures] readonly attribute DOMString? region;
 
     // Non-standard
     [MeasureAs=MouseEventFromElement] readonly attribute Node fromElement;
     [MeasureAs=MouseEventToElement] readonly attribute Node toElement;
     [MeasureAs=MouseEventWhich] readonly attribute long which;
     [Measure] readonly attribute long layerX;
     [Measure] readonly attribute long layerY;
 };