DevicePoseProvider: be picky about locations (#1344)

* Only take updated location when it is of better quality

* Rename to AndroidLocation for clarification

* be pedantic about licenses

core/devicepose/src/main/java/de/mm20/launcher2/devicepose/DevicePoseProvider.kt

@@ -18,6 +18,8 @@ import kotlinx.coroutines.channels.awaitClose
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.callbackFlow
 import kotlinx.coroutines.flow.channelFlow
+import de.mm20.launcher2.ktx.foldOrNull
+import de.mm20.launcher2.ktx.isBetterThan
 import kotlinx.coroutines.flow.combine
 
 class DevicePoseProvider internal constructor(
@@ -37,10 +39,16 @@ class DevicePoseProvider internal constructor(
     }
 
     fun getLocation(minTimeMs: Long = 1000, minDistanceM: Float = 1f) = channelFlow {
+        fun updateLocation(update: Location?) {
+            if (update == null) return
+            if (!update.isBetterThan(lastLocation)) return
+            lastLocation = update
+            updateDeclination(update)
+            trySend(update)
+        }
+
         val locationCallback = LocationListenerCompat {
-            lastLocation = it
+            updateLocation(it)
-            updateDeclination(it)
-            trySend(it)
         }
 
         context.getSystemService<LocationManager>()
@@ -50,20 +58,14 @@ class DevicePoseProvider internal constructor(
                 val hasCoarseAccess =
                     context.checkPermission(Manifest.permission.ACCESS_COARSE_LOCATION)
 
-                val location =
+                val previousLocation =
-                    (if (hasFineAccess) this@runCatching.getLastKnownLocation(LocationManager.GPS_PROVIDER) else null)
+                    hasFineAccess.foldOrNull { getLastKnownLocation(LocationManager.GPS_PROVIDER) } ?:
-                        ?: if (hasCoarseAccess) this@runCatching.getLastKnownLocation(
+                    hasCoarseAccess.foldOrNull { getLastKnownLocation(LocationManager.NETWORK_PROVIDER) }
-                            LocationManager.NETWORK_PROVIDER
-                        ) else null
 
-                if (location != null) {
+                updateLocation(previousLocation)
-                    lastLocation = location
-                    updateDeclination(location)
-                    trySend(location)
-                }
 
                 if (hasFineAccess) {
-                    this@runCatching.requestLocationUpdates(
+                    requestLocationUpdates(
                         LocationManager.GPS_PROVIDER,
                         minTimeMs,
                         minDistanceM,
@@ -71,7 +73,7 @@ class DevicePoseProvider internal constructor(
                     )
                 }
                 if (hasCoarseAccess) {
-                    this@runCatching.requestLocationUpdates(
+                    requestLocationUpdates(
                         LocationManager.NETWORK_PROVIDER,
                         minTimeMs,
                         minDistanceM,

core/ktx/src/main/java/de/mm20/launcher2/ktx/AndroidLocation.kt

@@ -0,0 +1,37 @@
+package de.mm20.launcher2.ktx
+
+import kotlin.time.Duration.Companion.minutes
+import kotlin.time.Duration.Companion.nanoseconds
+
+import android.location.Location as AndroidLocation
+
+/* https://github.com/streetcomplete/StreetComplete/blob/master/app/src/main/java/de/westnordost/streetcomplete/util/location/LocationUtils.kt
+ * GPL-3.0-or-later
+ */
+fun AndroidLocation.isBetterThan(previous: AndroidLocation?): Boolean {
+    if (longitude.isNaN() || latitude.isNaN()) return false
+    if (previous == null) return true
+
+    val locationTimeDiff = elapsedRealtimeNanos.nanoseconds - previous.elapsedRealtimeNanos.nanoseconds
+    val isMuchNewer = locationTimeDiff > 2.minutes
+    val isMuchOlder = locationTimeDiff < (-2).minutes
+    val isNewer = locationTimeDiff.isPositive()
+
+    val accuracyDelta = accuracy - previous.accuracy
+    val isLessAccurate = accuracyDelta > 0f
+    val isMoreAccurate = accuracyDelta < 0f
+    val isMuchLessAccurate = accuracyDelta > 200f
+
+    val isFromSameProvider = provider == previous.provider
+
+    return when {
+        // the user has likely moved
+        isMuchNewer -> true
+        // If the new location is more than two minutes older, it must be worse
+        isMuchOlder -> false
+        isMoreAccurate -> true
+        isNewer && !isLessAccurate -> true
+        isNewer && !isMuchLessAccurate && isFromSameProvider -> true
+        else -> false
+    }
+}

core/ktx/src/main/java/de/mm20/launcher2/ktx/Boolean.kt

@@ -1,5 +1,14 @@
 package de.mm20.launcher2.ktx
 
-inline fun Boolean.toInt(): Int {
+fun Boolean.toInt(): Int {
     return if (this) 1 else 0
-}
+}
+
+fun <T> Boolean.fold(
+    whenTrue: () -> T,
+    otherwise: () -> T
+): T = if (this) whenTrue() else otherwise()
+
+fun <T> Boolean.foldOrNull(
+    whenTrue: () -> T
+): T? = fold(whenTrue) { null }