content/browser/geolocation/win7_location_provider_win.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "content/browser/geolocation/win7_location_provider_win.h"
   6
   7 #include <algorithm>
   8 #include <cmath>
   9
  10 #include "base/bind.h"
  11 #include "base/compiler_specific.h"
  12 #include "base/logging.h"
  13 #include "base/message_loop.h"
  14
  15 namespace content {
  16 namespace {
  17
  18 const int kPollPeriodMovingMillis = 500;
  19 // Poll less frequently whilst stationary.
  20 const int kPollPeriodStationaryMillis = kPollPeriodMovingMillis * 3;
  21 // Reading must differ by more than this amount to be considered movement.
  22 const int kMovementThresholdMeters = 20;
  23
  24 // This algorithm is reused from the corresponding code in the Gears project
  25 // and is also used in gps_location_provider_linux.cc
  26 // The arbitrary delta is decreased (Gears used 100 meters); if we need to
  27 // decrease it any further we'll likely want to do some smarter filtering to
  28 // remove GPS location jitter noise.
  29 bool PositionsDifferSiginificantly(const Geoposition& position_1,
  30                                    const Geoposition& position_2) {
  31   const bool pos_1_valid = position_1.Validate();
  32   if (pos_1_valid != position_2.Validate())
  33     return true;
  34   if (!pos_1_valid) {
  35     DCHECK(!position_2.Validate());
  36     return false;
  37   }
  38   double delta = std::sqrt(
  39       std::pow(std::fabs(position_1.latitude - position_2.latitude), 2) +
  40       std::pow(std::fabs(position_1.longitude - position_2.longitude), 2));
  41   // Convert to meters. 1 minute of arc of latitude (or longitude at the
  42   // equator) is 1 nautical mile or 1852m.
  43   delta *= 60 * 1852;
  44   return delta > kMovementThresholdMeters;
  45 }
  46 }
  47
  48 Win7LocationProvider::Win7LocationProvider(Win7LocationApi* api)
  49     : ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)) {
  50   DCHECK(api != NULL);
  51   api_.reset(api);
  52 }
  53
  54 Win7LocationProvider::~Win7LocationProvider() {
  55   api_.reset();
  56 }
  57
  58 bool Win7LocationProvider::StartProvider(bool high_accuracy){
  59   if (api_ == NULL)
  60     return false;
  61   api_->SetHighAccuracy(high_accuracy);
  62   if (!weak_factory_.HasWeakPtrs())
  63     ScheduleNextPoll(0);
  64   return true;
  65 }
  66
  67 void Win7LocationProvider::StopProvider() {
  68   weak_factory_.InvalidateWeakPtrs();
  69 }
  70
  71 void Win7LocationProvider::GetPosition(Geoposition* position) {
  72   DCHECK(position);
  73   *position = position_;
  74 }
  75
  76 void Win7LocationProvider::UpdatePosition() {
  77   ScheduleNextPoll(0);
  78 }
  79
  80 void Win7LocationProvider::DoPollTask() {
  81   Geoposition new_position;
  82   api_->GetPosition(&new_position);
  83   const bool differ = PositionsDifferSiginificantly(position_, new_position);
  84   ScheduleNextPoll(differ ? kPollPeriodMovingMillis :
  85                             kPollPeriodStationaryMillis);
  86   if (differ || new_position.error_code != Geoposition::ERROR_CODE_NONE) {
  87     // Update if the new location is interesting or we have an error to report
  88     position_ = new_position;
  89     UpdateListeners();
  90   }
  91 }
  92
  93 void Win7LocationProvider::ScheduleNextPoll(int interval) {
  94   MessageLoop::current()->PostDelayedTask(
  95       FROM_HERE,
  96       base::Bind(&Win7LocationProvider::DoPollTask, weak_factory_.GetWeakPtr()),
  97       base::TimeDelta::FromMilliseconds(interval));
  98 }
  99
 100 LocationProviderBase* NewSystemLocationProvider() {
 101   Win7LocationApi* api = Win7LocationApi::Create();
 102   if (api == NULL)
 103     return NULL; // API not supported on this machine.
 104   return new Win7LocationProvider(api);
 105 }
 106
 107 }  // namespace content