Add Polygons(states) for registering many polygons at once

api/android-sdk-compose.api

@@ -84,6 +84,7 @@ public final class com.mapconductor.compose.polygon.LocalPolygonCollectorKt {
 }
 public final class com.mapconductor.compose.polygon.PolygonComponentKt {
   public static final void Polygon(com.mapconductor.compose.MapViewScope, com.mapconductor.core.polygon.PolygonState, androidx.compose.runtime.Composer, int);
+  public static final void Polygons(com.mapconductor.compose.MapViewScope, java.util.List<com.mapconductor.core.polygon.PolygonState>, androidx.compose.runtime.Composer, int);
   public static final void Polygon-YoVAMyA(com.mapconductor.compose.MapViewScope, java.util.List<? extends com.mapconductor.core.features.GeoPointInterface>, java.util.List<? extends java.util.List<? extends com.mapconductor.core.features.GeoPointInterface>>, java.lang.String, long, float, long, boolean, int, java.io.Serializable, kotlin.jvm.functions.Function1<? super com.mapconductor.core.polygon.PolygonEvent, kotlin.Unit>, androidx.compose.runtime.Composer, int, int, int);
   public static final void Polygon-IvR-a-0(com.mapconductor.compose.MapViewScope, com.mapconductor.core.features.GeoRectBounds, java.lang.String, long, float, long, boolean, int, java.io.Serializable, kotlin.jvm.functions.Function1<? super com.mapconductor.core.polygon.PolygonEvent, kotlin.Unit>, androidx.compose.runtime.Composer, int, int);
 }

src/main/java/com/mapconductor/compose/polygon/PolygonComponent.kt

@@ -3,6 +3,8 @@ package com.mapconductor.compose.polygon
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
@@ -14,6 +16,9 @@ import com.mapconductor.core.polygon.OnPolygonEventHandler
 import com.mapconductor.core.polygon.PolygonState
 import com.mapconductor.core.polygon.unionHolesInPlace
 import java.io.Serializable
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.flow.update
+import kotlinx.coroutines.withContext
 
 @Composable
 fun MapViewScope.Polygon(state: PolygonState) {
@@ -32,6 +37,57 @@ fun MapViewScope.Polygon(state: PolygonState) {
     }
 }
 
+/**
+ * Efficiently add many polygons without creating one Composable per polygon.
+ *
+ * The same shape as [com.mapconductor.compose.marker.Markers]: one effect diffs
+ * the list against the ids this call added last time and publishes the result
+ * in a single collector update.
+ */
+@Composable
+fun MapViewScope.Polygons(states: List<PolygonState>) {
+    val collector = LocalPolygonCollector.current
+    val prevIdsState = remember { mutableStateOf<Set<String>>(emptySet()) }
+
+    LaunchedEffect(states) {
+        withContext(Dispatchers.Default) {
+            val prevIds = prevIdsState.value
+            val nextIds = states.asSequence().map { it.id }.toSet()
+            val removedIds = prevIds - nextIds
+            // Union the holes once per newly added state, as Polygon(state) does.
+            for (state in states) {
+                if (state.id !in prevIds && state.holes.size > 1) {
+                    state.unionHolesInPlace()
+                }
+            }
+            prevIdsState.value = nextIds
+            // Merge only the ids this Polygons() owns, so several
+            // Polygons()/Polygon() can share one map's collector.
+            collector.flow.update { current ->
+                val next = current.toMutableMap()
+                for (id in removedIds) next.remove(id)
+                for (state in states) next[state.id] = state
+                next
+            }
+        }
+    }
+
+    DisposableEffect(Unit) {
+        onDispose {
+            // Remove only the polygons this Polygons() owns on dispose.
+            val ownIds = prevIdsState.value
+            if (ownIds.isNotEmpty()) {
+                collector.flow.update { current ->
+                    val next = current.toMutableMap()
+                    for (id in ownIds) next.remove(id)
+                    next
+                }
+            }
+            prevIdsState.value = emptySet()
+        }
+    }
+}
+
 @Composable
 fun MapViewScope.Polygon(
     points: List<GeoPointInterface>,