Fix motion event orientation handling for styluses.

ui/events/blink/blink_event_util.cc

 // 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.
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include "ui/events/blink/blink_event_util.h"
 
 #include <cmath>
@@ skipping 85 matching lines @@
   float major_radius = event.GetTouchMajor(pointer_index) / 2.f;
   float minor_radius = event.GetTouchMinor(pointer_index) / 2.f;
 
   DCHECK_LE(minor_radius, major_radius);
   DCHECK_IMPLIES(major_radius, minor_radius);
 
   float orientation_deg = event.GetOrientation(pointer_index) * 180.f / M_PI;
   DCHECK_GE(major_radius, 0);
   DCHECK_GE(minor_radius, 0);
   DCHECK_GE(major_radius, minor_radius);
+  // Orientation lies in [-90, 90] for a touch screen or pad and in [-180, 180]
+  // for a stylus.
   // Allow a small bound tolerance to account for floating point conversion.
-  DCHECK_GT(orientation_deg, -90.01f);
-  DCHECK_LT(orientation_deg, 90.01f);
+  DCHECK_GT(orientation_deg, -180.01f);

[jdduke (slow), 2015/05/28 15:01:45]

I spoke offline with mustaq/tdresser. We decided it might be simplest for us to
proceed with this solution, however, we should restrict the validation to match
the Android spec. So this will look like:

if (event.GetToolType(pointer_index) == MotionEvent::TOOL_TYPE_STYLUS) {
  *insert code you have now*
} else {
  * insert old [90, 90] validation code *
}

[USE eero AT chromium.org, 2015/05/29 10:49:30]

Done.

+  DCHECK_LT(orientation_deg, 180.01f);
+  if (orientation_deg >= 90.f)

[jdduke (slow), 2015/05/28 15:01:45]

Let's make this a strict inequality (>, <).

[USE eero AT chromium.org, 2015/05/29 10:49:30]

Actually, this one should not be a strict inequality.
According to the TouchEvent spec, rotationAngle must be less than (and not equal
to) 90.

+    orientation_deg -= 180.f;
+  if (orientation_deg <= -90.f)

[USE eero AT chromium.org, 2015/05/29 10:49:30]

But this should be a strict inequality.
Done.

+    orientation_deg += 180.f;
   if (orientation_deg >= 0) {
     // The case orientation_deg == 0 is handled here on purpose: although the
     // 'else' block is equivalent in this case, we want to pass the 0 value
     // unchanged (and 0 is the default value for many devices that don't
     // report elliptical touches).
     touch.radiusX = minor_radius;
     touch.radiusY = major_radius;
     touch.rotationAngle = orientation_deg;
   } else {
     touch.radiusX = major_radius;
@@ skipping 175 matching lines @@
 }
 
 WebGestureEvent CreateWebGestureEventFromGestureEventData(
     const GestureEventData& data) {
   return CreateWebGestureEvent(data.details, data.time - base::TimeTicks(),
                                gfx::PointF(data.x, data.y),
                                gfx::PointF(data.raw_x, data.raw_y), data.flags);
 }
 
 }  // namespace ui