Adding pref to store the user-selected proximity threshold.

components/proximity_auth/proximity_monitor_impl.cc

Index: components/proximity_auth/proximity_monitor_impl.cc
diff --git a/components/proximity_auth/proximity_monitor_impl.cc b/components/proximity_auth/proximity_monitor_impl.cc
index 202be9defe0de6ae3fb285a3e81bcb71d66a61c9..3326990757f29a9620207c5b6f135b56b218f06f 100644
--- a/components/proximity_auth/proximity_monitor_impl.cc
+++ b/components/proximity_auth/proximity_monitor_impl.cc
@@ -12,6 +12,8 @@
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/tick_clock.h"
 #include "base/time/time.h"
+#include "chrome/common/pref_names.h"
+#include "components/prefs/pref_service.h"
 #include "components/proximity_auth/logging/logging.h"
 #include "components/proximity_auth/metrics.h"
 #include "components/proximity_auth/proximity_monitor_observer.h"
@@ -34,13 +36,20 @@ const int kRssiThreshold = -70;
 // The weight of the most recent RSSI sample.
 const double kRssiSampleWeight = 0.3;
 
+// These are arbitrary labels displayed in the settings page for the user
+// to select. The correspondence to actual RSSI values is done in the
+// GetRssiThresholdFromPrefs().
+enum ProximityThreshold { kVeryClose = 0, kClose = 1, kFar = 2, kVeryFar = 3 };
+
 ProximityMonitorImpl::ProximityMonitorImpl(
     cryptauth::Connection* connection,
-    std::unique_ptr<base::TickClock> clock)
+    std::unique_ptr<base::TickClock> clock,
+    PrefService* pref_service)
     : connection_(connection),
       remote_device_is_in_proximity_(false),
       is_active_(false),
       clock_(std::move(clock)),
+      pref_service_(pref_service),
       polling_weak_ptr_factory_(this),
       weak_ptr_factory_(this) {
   if (device::BluetoothAdapterFactory::IsBluetoothSupported()) {
@@ -58,6 +67,7 @@ ProximityMonitorImpl::~ProximityMonitorImpl() {
 
 void ProximityMonitorImpl::Start() {
   is_active_ = true;
+  GetRssiThresholdFromPrefs();
   UpdatePollingState();
 }
 
@@ -206,4 +216,24 @@ void ProximityMonitorImpl::CheckForProximityStateChange() {
   }
 }
 
+void ProximityMonitorImpl::GetRssiThresholdFromPrefs() {
+  int pref_value =
+      pref_service_->GetInteger(prefs::kEasyUnlockProximityThreshold);
+  ProximityThreshold threshold = static_cast<ProximityThreshold>(pref_value);
+  switch (threshold) {

[Tim Song, 2017/07/07 21:48:24]

Add a default case as well.

[sacomoto, 2017/07/10 16:54:07]

Done.

+    case ProximityThreshold::kVeryClose:
+      rssi_threshold_ = -55;

[Tim Song, 2017/07/07 21:48:24]

I would spread out these values out a bit more. Perhaps something like:

{ -30, -50, -70, -85 }

This way we can cover more combinations of devices.

[sacomoto, 2017/07/10 16:54:07]

I spread it a bit more, but I think -30 is really unrealistic. 

+      return;
+    case ProximityThreshold::kClose:
+      rssi_threshold_ = -65;
+      return;
+    case ProximityThreshold::kFar:
+      rssi_threshold_ = -75;
+      return;
+    case ProximityThreshold::kVeryFar:
+      rssi_threshold_ = -85;
+      return;
+  }
+}
+
 }  // namespace proximity_auth