Working box by features

src/commonMain/kotlin/centre/sciprog/maps/GmcBox.kt

@@ -1,8 +1,8 @@
 package centre.sciprog.maps
 
-import kotlin.math.abs
-import kotlin.math.max
-import kotlin.math.min
+import androidx.compose.ui.unit.DpSize
+import centre.sciprog.maps.compose.MapFeature
+import kotlin.math.*
 
 class GmcBox(val a: GeodeticMapCoordinates, val b: GeodeticMapCoordinates)
 
@@ -28,9 +28,10 @@ val GmcBox.width get() = abs(a.longitude - b.longitude)
 val GmcBox.height get() = abs(a.latitude - b.latitude)
 
 /**
- * Compute a minimal bounding box including all given boxes
+ * Compute a minimal bounding box including all given boxes. Return null if collection is empty
  */
-fun Iterable<GmcBox>.wrapAll(): GmcBox {
+fun Collection<GmcBox>.wrapAll(): GmcBox? {
+    if (isEmpty()) return null
     //TODO optimize computation
     val minLat = minOf { it.bottom }
     val maxLat = maxOf { it.top }

src/commonMain/kotlin/centre/sciprog/maps/compose/MapFeature.kt

@@ -17,7 +17,7 @@ sealed class MapFeature(val zoomRange: IntRange) {
     abstract fun getBoundingBox(zoom: Int): GmcBox
 }
 
-fun Iterable<MapFeature>.computeBoundingBox(zoom: Int): GmcBox = map { it.getBoundingBox(zoom) }.wrapAll()
+fun Iterable<MapFeature>.computeBoundingBox(zoom: Int): GmcBox? = map { it.getBoundingBox(zoom) }.wrapAll()
 
 internal fun Pair<Double, Double>.toCoordinates() = GeodeticMapCoordinates.ofDegrees(first, second)
 

src/commonMain/kotlin/centre/sciprog/maps/compose/MapView.kt

@@ -12,6 +12,7 @@ import kotlin.math.min
 
 data class MapViewConfig(
     val zoomSpeed: Double = 1.0 / 3.0,
+    val inferViewBoxFromFeatures: Boolean = false
 )
 
 @Composable
@@ -62,27 +63,4 @@ fun MapView(
         MapViewPoint(box.center, zoom)
     }
     MapView(mapTileProvider, computeViewPoint, featuresBuilder.build(), onClick, config, modifier)
-}
-
-/**
- * Create a MapView with initial [MapViewPoint] inferred from features
- *
- * @param defaultZoom the zoom, for which the bounding box is computed
- */
-@Composable
-fun MapViewWithFeatures(
-    mapTileProvider: MapTileProvider,
-    features: Map<FeatureId, MapFeature> = emptyMap(),
-    onClick: (GeodeticMapCoordinates) -> Unit = {},
-    config: MapViewConfig = MapViewConfig(),
-    defaultZoom: Int = 1,
-    modifier: Modifier = Modifier.fillMaxSize(),
-    buildFeatures: @Composable (FeatureBuilder.() -> Unit),
-) {
-    val featuresBuilder = MapFeatureBuilder(features)
-    featuresBuilder.buildFeatures()
-    val featureSet = featuresBuilder.build()
-    if(featureSet.isEmpty()) error("Can't create `MapViewWithFeatures` from empty feature set")
-    val box: GmcBox = featureSet.values.map { it.getBoundingBox(defaultZoom) }.wrapAll()
-    MapView(mapTileProvider, box, features, onClick, config, modifier, buildFeatures)
 }

src/jvmMain/kotlin/Main.kt

@@ -10,7 +10,6 @@ import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.window.Window
 import androidx.compose.ui.window.application
 import centre.sciprog.maps.GeodeticMapCoordinates
-import centre.sciprog.maps.GmcBox
 import centre.sciprog.maps.MapViewPoint
 import centre.sciprog.maps.compose.*
 import io.ktor.client.HttpClient
@@ -41,7 +40,12 @@ fun App() {
         Column {
             //display click coordinates
             Text(coordinates?.toString() ?: "")
-            MapViewWithFeatures(mapTileProvider, onClick = { gmc: GeodeticMapCoordinates -> coordinates = gmc }) {
+            MapView(
+                mapTileProvider,
+                viewPoint,
+                onClick = { gmc -> coordinates = gmc },
+                config = MapViewConfig(inferViewBoxFromFeatures = true)
+            ) {
                 val pointOne = 55.568548 to 37.568604
                 val pointTwo = 55.929444 to 37.518434
 

src/jvmMain/kotlin/centre/sciprog/maps/compose/MapViewJvm.kt

@@ -20,10 +20,7 @@ import centre.sciprog.maps.*
 import mu.KotlinLogging
 import org.jetbrains.skia.Font
 import org.jetbrains.skia.Paint
-import kotlin.math.ceil
-import kotlin.math.floor
-import kotlin.math.log2
-import kotlin.math.pow
+import kotlin.math.*
 
 
 private fun Color.toPaint(): Paint = Paint().apply {
@@ -48,7 +45,21 @@ actual fun MapView(
 ) {
     var canvasSize by remember { mutableStateOf(DpSize(512.dp, 512.dp)) }
 
-    var viewPointOverride by remember { mutableStateOf<MapViewPoint?>(null) }
+    var viewPointOverride by remember { mutableStateOf<MapViewPoint?>(
+        if(config.inferViewBoxFromFeatures){
+            features.values.computeBoundingBox(1)?.let { box ->
+                val zoom = log2(
+                    min(
+                        canvasSize.width.value / box.width,
+                        canvasSize.height.value / box.height
+                    ) * PI / mapTileProvider.tileSize
+                )
+                MapViewPoint(box.center, zoom)
+            }
+        } else {
+            null
+        }
+    ) }
 
     val viewPoint by derivedStateOf { viewPointOverride ?: computeViewPoint(canvasSize) }