[WIP] bounding boxes

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

@@ -43,6 +43,8 @@ public class GeodeticMapCoordinates private constructor(public val latitude: Dou
     }
 }
 
+internal typealias Gmc = GeodeticMapCoordinates
+
 
 //public interface GeoToScreenConversion {
 //    public fun getScreenX(gmc: GeodeticMapCoordinates): Double

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

@@ -0,0 +1,35 @@
+package centre.sciprog.maps
+
+import kotlin.math.max
+import kotlin.math.min
+
+class GmcBox(val a: GeodeticMapCoordinates, val b: GeodeticMapCoordinates)
+
+fun GmcBox(latitudes: ClosedFloatingPointRange<Double>, longitudes: ClosedFloatingPointRange<Double>) = GmcBox(
+    Gmc.ofRadians(latitudes.start, longitudes.start),
+    Gmc.ofRadians(latitudes.endInclusive, longitudes.endInclusive)
+)
+
+val GmcBox.center
+    get() = GeodeticMapCoordinates.ofRadians(
+        (a.latitude + b.latitude) / 2,
+        (a.longitude + b.longitude) / 2
+    )
+
+val GmcBox.left get() = min(a.longitude, b.longitude)
+val GmcBox.right get() = max(a.longitude, b.longitude)
+
+val GmcBox.top get() = max(a.latitude, b.latitude)
+val GmcBox.bottom get() = min(a.latitude, b.latitude)
+
+/**
+ * Compute a minimal bounding box including all given boxes
+ */
+fun Iterable<GmcBox>.wrapAll(): GmcBox {
+    //TODO optimize computation
+    val minLat = minOf { it.bottom }
+    val maxLat = maxOf { it.top }
+    val minLong = minOf { it.left }
+    val maxLong = maxOf { it.right }
+    return GmcBox(maxLat..maxLat, minLong..maxLong)
+}

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

@@ -9,9 +9,15 @@ import androidx.compose.ui.graphics.vector.VectorPainter
 import androidx.compose.ui.graphics.vector.rememberVectorPainter
 import androidx.compose.ui.unit.IntSize
 import centre.sciprog.maps.GeodeticMapCoordinates
+import centre.sciprog.maps.GmcBox
+import centre.sciprog.maps.wrapAll
 
 //TODO replace zoom range with zoom-based representation change
-sealed class MapFeature(val zoomRange: IntRange)
+sealed class MapFeature(val zoomRange: IntRange) {
+    abstract fun getBoundingBox(zoom: Int): GmcBox
+}
+
+fun Iterable<MapFeature>.computeBoundingBox(zoom: Int): GmcBox = map { it.getBoundingBox(zoom) }.wrapAll()
 
 internal fun Pair<Double, Double>.toCoordinates() = GeodeticMapCoordinates.ofDegrees(first, second)
 
@@ -20,35 +26,46 @@ internal val defaultZoomRange = 1..18
 /**
  * A feature that decides what to show depending on the zoom value (it could change size of shape)
  */
-class MapFeatureSelector(val selector: (zoom: Int) -> MapFeature) : MapFeature(defaultZoomRange)
+class MapFeatureSelector(val selector: (zoom: Int) -> MapFeature) : MapFeature(defaultZoomRange) {
+    override fun getBoundingBox(zoom: Int): GmcBox = selector(zoom).getBoundingBox(zoom)
+
+}
 
 class MapCircleFeature(
     val center: GeodeticMapCoordinates,
     zoomRange: IntRange = defaultZoomRange,
     val size: Float = 5f,
     val color: Color = Color.Red,
-) : MapFeature(zoomRange)
+) : MapFeature(zoomRange) {
+    override fun getBoundingBox(zoom: Int): GmcBox = GmcBox(center, center)
+}
 
 class MapLineFeature(
     val a: GeodeticMapCoordinates,
     val b: GeodeticMapCoordinates,
     zoomRange: IntRange = defaultZoomRange,
     val color: Color = Color.Red,
-) : MapFeature(zoomRange)
+) : MapFeature(zoomRange) {
+    override fun getBoundingBox(zoom: Int): GmcBox = GmcBox(a, b)
+}
 
 class MapTextFeature(
     val position: GeodeticMapCoordinates,
     val text: String,
     zoomRange: IntRange = defaultZoomRange,
     val color: Color = Color.Red,
-) : MapFeature(zoomRange)
+) : MapFeature(zoomRange) {
+    override fun getBoundingBox(zoom: Int): GmcBox = GmcBox(position, position)
+}
 
 class MapBitmapImageFeature(
     val position: GeodeticMapCoordinates,
     val image: ImageBitmap,
     val size: IntSize = IntSize(15, 15),
     zoomRange: IntRange = defaultZoomRange,
-) : MapFeature(zoomRange)
+) : MapFeature(zoomRange) {
+    override fun getBoundingBox(zoom: Int): GmcBox = GmcBox(position, position)
+}
 
 
 class MapVectorImageFeature internal constructor(
@@ -56,7 +73,9 @@ class MapVectorImageFeature internal constructor(
     val painter: VectorPainter,
     val size: Size,
     zoomRange: IntRange = defaultZoomRange,
-) : MapFeature(zoomRange)
+) : MapFeature(zoomRange) {
+    override fun getBoundingBox(zoom: Int): GmcBox = GmcBox(position, position)
+}
 
 @Composable
 fun MapVectorImageFeature(