From 4ebd5168946ec7cc41cbc92f6c10d05c55cdbc33 Mon Sep 17 00:00:00 2001
From: Rory Stephenson <rorystephenson@gmail.com>
Date: Mon, 19 Jun 2023 10:40:27 +0200
Subject: [PATCH] Pre-calculate Marker's Anchor

This allows Marker to accept the same anchor argument as MarkerLayer,
anchorPos, whilst still precalculating the Anchor so it isn't calculated
on every build.

Co-authored-by: Luka S <github@jaffaketchup.dev>
---
 example/lib/pages/markers.dart  |  9 +++------
 lib/src/layer/marker_layer.dart | 15 +++++++++------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/example/lib/pages/markers.dart b/example/lib/pages/markers.dart
index 2300ede69..df79fedc4 100644
--- a/example/lib/pages/markers.dart
+++ b/example/lib/pages/markers.dart
@@ -129,8 +129,7 @@ class MarkerPageState extends State<MarkerPage> {
                             47.18664724067855, -1.5436768515939427),
                         width: 64,
                         height: 64,
-                        anchor: Anchor.fromPos(
-                            AnchorPos.align(AnchorAlign.left), 64, 64),
+                        anchorPos: AnchorPos.align(AnchorAlign.left),
                         builder: (context) => const ColoredBox(
                           color: Colors.lightBlue,
                           child: Align(
@@ -144,8 +143,7 @@ class MarkerPageState extends State<MarkerPage> {
                             47.18664724067855, -1.5436768515939427),
                         width: 64,
                         height: 64,
-                        anchor: Anchor.fromPos(
-                            AnchorPos.align(AnchorAlign.right), 64, 64),
+                        anchorPos: AnchorPos.align(AnchorAlign.right),
                         builder: (context) => const ColoredBox(
                           color: Colors.pink,
                           child: Align(
@@ -158,8 +156,7 @@ class MarkerPageState extends State<MarkerPage> {
                         point: const LatLng(
                             47.18664724067855, -1.5436768515939427),
                         rotate: false,
-                        anchor: Anchor.fromPos(
-                            AnchorPos.align(AnchorAlign.center), 30, 30),
+                        anchorPos: AnchorPos.align(AnchorAlign.center),
                         builder: (context) =>
                             const ColoredBox(color: Colors.black),
                       ),
diff --git a/lib/src/layer/marker_layer.dart b/lib/src/layer/marker_layer.dart
index e523b4b9f..b94afdd89 100644
--- a/lib/src/layer/marker_layer.dart
+++ b/lib/src/layer/marker_layer.dart
@@ -10,11 +10,13 @@ import 'package:latlong2/latlong.dart';
 /// Can be defined exactly (using [AnchorPos.exactly] with an [Anchor]) or in
 /// a relative alignment (using [AnchorPos.align] with an [AnchorAlign]).
 class AnchorPos {
+  static const defaultAnchorPos = AnchorPos.align(AnchorAlign.center);
+
   final Anchor? anchor;
   final AnchorAlign? alignment;
 
-  AnchorPos.exactly(Anchor this.anchor) : alignment = null;
-  AnchorPos.align(AnchorAlign this.alignment) : anchor = null;
+  const AnchorPos.exactly(Anchor this.anchor) : alignment = null;
+  const AnchorPos.align(AnchorAlign this.alignment) : anchor = null;
 }
 
 /// Exact alignment for a [Marker.builder] widget relative to the center
@@ -26,7 +28,7 @@ class Anchor {
   final double left;
   final double top;
 
-  Anchor(this.left, this.top);
+  const Anchor(this.left, this.top);
 
   factory Anchor.fromPos(AnchorPos pos, double width, double height) {
     if (pos.anchor case final anchor?) return anchor;
@@ -131,11 +133,12 @@ class Marker {
     required this.builder,
     this.width = 30.0,
     this.height = 30.0,
-    this.anchor,
+    AnchorPos? anchorPos,
     this.rotate,
     this.rotateOrigin,
     this.rotateAlignment,
-  });
+  }) : anchor =
+            anchorPos == null ? null : Anchor.fromPos(anchorPos, width, height);
 }
 
 class MarkerLayer extends StatelessWidget {
@@ -202,7 +205,7 @@ class MarkerLayer extends StatelessWidget {
       // unlike the map coordinates.
       final anchor = marker.anchor ??
           Anchor.fromPos(
-            anchorPos ?? AnchorPos.align(AnchorAlign.center),
+            anchorPos ?? AnchorPos.defaultAnchorPos,
             marker.width,
             marker.height,
           );