feat: add map `ScaleBarOverlay`

app/src/main/java/com/geeksville/mesh/ui/map/MapFragment.kt

@@ -30,6 +30,7 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.hapticfeedback.HapticFeedbackType
 import androidx.compose.ui.platform.ComposeView
 import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.platform.LocalHapticFeedback
 import androidx.compose.ui.platform.ViewCompositionStrategy
 import androidx.compose.ui.unit.dp
@@ -85,6 +86,7 @@ import org.osmdroid.views.overlay.mylocation.MyLocationNewOverlay
 import com.geeksville.mesh.model.map.clustering.RadiusMarkerClusterer
 import com.geeksville.mesh.util.addCopyright
 import com.geeksville.mesh.util.addMapEventListener
+import com.geeksville.mesh.util.addScaleBarOverlay
 import com.geeksville.mesh.util.createLatLongGrid
 import java.io.File
 import java.text.DateFormat
@@ -230,6 +232,7 @@ fun MapView(
     var myLocationOverlay: MyLocationNewOverlay? by remember { mutableStateOf(null) }
 
     val context = LocalContext.current
+    val density = LocalDensity.current
     val mPrefs = remember { context.getSharedPreferences(prefsName, Context.MODE_PRIVATE) }
 
     val haptic = LocalHapticFeedback.current
@@ -441,6 +444,7 @@ fun MapView(
         }
 
         addCopyright() // Copyright is required for certain map sources
+        addScaleBarOverlay(density)
         createLatLongGrid(false)
 
         invalidate()

app/src/main/java/com/geeksville/mesh/util/MapViewExtensions.kt

@@ -2,12 +2,17 @@ package com.geeksville.mesh.util
 
 import android.graphics.Color
 import android.graphics.Paint
+import android.graphics.Typeface
+import androidx.compose.ui.unit.Density
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
 import org.osmdroid.events.DelayedMapListener
 import org.osmdroid.events.MapListener
 import org.osmdroid.events.ScrollEvent
 import org.osmdroid.events.ZoomEvent
 import org.osmdroid.views.MapView
 import org.osmdroid.views.overlay.CopyrightOverlay
+import org.osmdroid.views.overlay.ScaleBarOverlay
 import org.osmdroid.views.overlay.gridlines.LatLonGridlineOverlay2
 
 /**
@@ -45,6 +50,23 @@ fun MapView.createLatLongGrid(enabled: Boolean) {
     }
 }
 
+fun MapView.addScaleBarOverlay(density: Density) {
+    if (overlays.none { it is ScaleBarOverlay }) {
+        val scaleBarOverlay = ScaleBarOverlay(this).apply {
+            setAlignBottom(true)
+            with(density) {
+                setScaleBarOffset(15.dp.toPx().toInt(), 40.dp.toPx().toInt())
+                setTextSize(12.sp.toPx())
+            }
+            textPaint.apply {
+                isAntiAlias = true
+                typeface = Typeface.DEFAULT_BOLD
+            }
+        }
+        overlays.add(scaleBarOverlay)
+    }
+}
+
 private const val INACTIVITY_DELAY_MILLIS = 500L
 fun MapView.addMapEventListener(onEvent: () -> Unit) {
     addMapListener(DelayedMapListener(object : MapListener {