Refactors DeviceOrientation to make it more extensible

content/browser/device_orientation/orientation.cc

+// Copyright (c) 2012 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.
+
+#include "content/browser/device_orientation/orientation.h"
+
+#include <cmath>
+
+#include "content/common/device_orientation_messages.h"
+
+namespace device_orientation {
+
+Orientation::Orientation()
+    : can_provide_alpha_(false),
+      can_provide_beta_(false),
+      can_provide_gamma_(false),
+      can_provide_absolute_(false) {
+}
+
+Orientation::~Orientation() {
+}
+
+IPC::Message* Orientation::CreateIPCMessage(int render_view_id) const {
+  DeviceOrientationMsg_Updated_Params params;
+  params.can_provide_alpha = can_provide_alpha_;
+  params.alpha = alpha_;
+  params.can_provide_beta = can_provide_beta_;
+  params.beta = beta_;
+  params.can_provide_gamma = can_provide_gamma_;
+  params.gamma = gamma_;
+  params.can_provide_absolute = can_provide_absolute_;
+  params.absolute = absolute_;
+
+  return new DeviceOrientationMsg_Updated(render_view_id, params);
+}
+
+// Returns true if two orientations are considered different enough that
+// observers should be notified of the new orientation.
+bool Orientation::ShouldFireEvent(const DeviceData* old_data) const {
+  scoped_refptr<const Orientation> old_orientation(
+      static_cast<const Orientation*>(old_data));
+
+  return IsElementSignificantlyDifferent(can_provide_alpha_,
+                                         old_orientation->can_provide_alpha(),
+                                         alpha_,
+                                         old_orientation->alpha()) ||
+        IsElementSignificantlyDifferent(can_provide_beta_,
+                                        old_orientation->can_provide_beta(),
+                                        beta_,
+                                        old_orientation->beta()) ||
+        IsElementSignificantlyDifferent(can_provide_gamma_,
+                                        old_orientation->can_provide_gamma(),
+                                        gamma_,
+                                        old_orientation->gamma()) ||
+        can_provide_absolute_ != old_orientation->can_provide_absolute() ||
+        absolute_ != old_orientation->absolute();
+}
+
+bool Orientation::IsElementSignificantlyDifferent(bool can_provide_element1,
+    bool can_provide_element2, double element1, double element2) {
+  const double kThreshold = 0.1;
+
+  if (can_provide_element1 != can_provide_element2)
+    return true;
+  if (can_provide_element1 && std::fabs(element1 - element2) >= kThreshold)
+    return true;
+  return false;
+}
+
+}  // namespace device_orientation