From 52bd69e7c574edb388645fef622bf67f8067e6e3 Mon Sep 17 00:00:00 2001
From: Steven Schoen <steven@stevenschoen.com>
Date: Thu, 19 Jan 2023 14:38:11 -0500
Subject: [PATCH] perf: Make CameraPositionState and MarkerState stable (#254)

---
 .../maps/android/compose/CameraPositionState.kt       |  8 ++++----
 .../java/com/google/maps/android/compose/Marker.kt    | 11 +++++++----
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/maps-compose/src/main/java/com/google/maps/android/compose/CameraPositionState.kt b/maps-compose/src/main/java/com/google/maps/android/compose/CameraPositionState.kt
index 0e6c893b..ed63b737 100644
--- a/maps-compose/src/main/java/com/google/maps/android/compose/CameraPositionState.kt
+++ b/maps-compose/src/main/java/com/google/maps/android/compose/CameraPositionState.kt
@@ -110,16 +110,16 @@ public class CameraPositionState(
 
     // Used to perform side effects thread-safely.
     // Guards all mutable properties that are not `by mutableStateOf`.
-    private val lock = Any()
+    private val lock = Unit
 
     // The map currently associated with this CameraPositionState.
     // Guarded by `lock`.
-    private var map: GoogleMap? = null
+    private var map: GoogleMap? by mutableStateOf(null)
 
     // An action to run when the map becomes available or unavailable.
     // represents a mutually exclusive mutation to perform while holding `lock`.
     // Guarded by `lock`.
-    private var onMapChanged: OnMapChangedCallback? = null
+    private var onMapChanged: OnMapChangedCallback? by mutableStateOf(null)
 
     /**
      * Set [onMapChanged] to [callback], invoking the current callback's
@@ -133,7 +133,7 @@ public class CameraPositionState(
     // A token representing the current owner of any ongoing motion in progress.
     // Used to determine if map animation should stop when calls to animate end.
     // Guarded by `lock`.
-    private var movementOwner: Any? = null
+    private var movementOwner: Any? by mutableStateOf(null)
 
     /**
      * Used with [onMapChangedLocked] to execute one-time actions when a map becomes available
diff --git a/maps-compose/src/main/java/com/google/maps/android/compose/Marker.kt b/maps-compose/src/main/java/com/google/maps/android/compose/Marker.kt
index e61c88fa..cc25422c 100644
--- a/maps-compose/src/main/java/com/google/maps/android/compose/Marker.kt
+++ b/maps-compose/src/main/java/com/google/maps/android/compose/Marker.kt
@@ -18,6 +18,7 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.ComposeNode
 import androidx.compose.runtime.CompositionContext
 import androidx.compose.runtime.Immutable
+import androidx.compose.runtime.MutableState
 import androidx.compose.runtime.currentComposer
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
@@ -81,13 +82,15 @@ public class MarkerState(
         internal set
 
     // The marker associated with this MarkerState.
-    internal var marker: Marker? = null
+    private val markerState: MutableState<Marker?> = mutableStateOf(null)
+    internal var marker: Marker?
+        get() = markerState.value
         set(value) {
-            if (field == null && value == null) return
-            if (field != null && value != null) {
+            if (markerState.value == null && value == null) return
+            if (markerState.value != null && value != null) {
                 error("MarkerState may only be associated with one Marker at a time.")
             }
-            field = value
+            markerState.value = value
         }
 
     /**