change anchor API to MarkerAnchor

flutter_map/flutter_map.iml

@@ -5,6 +5,7 @@
     <content url="file://$MODULE_DIR$">
       <excludeFolder url="file://$MODULE_DIR$/../fleaflet/.pub" />
       <excludeFolder url="file://$MODULE_DIR$/../fleaflet/build" />
+      <excludeFolder url="file://$MODULE_DIR$/.dart_tool" />
       <excludeFolder url="file://$MODULE_DIR$/.pub" />
       <excludeFolder url="file://$MODULE_DIR$/build" />
       <excludeFolder url="file://$MODULE_DIR$/../leaflet_flutter/.pub" />

flutter_map/lib/src/layer/marker_layer.dart

@@ -8,19 +8,69 @@ class MarkerLayerOptions extends LayerOptions {
   MarkerLayerOptions({this.markers = const []});
 }
 
+class Anchor {
+  final double left;
+  final double top;
+
+  Anchor(this.left, this.top);
+
+  Anchor._(double width, double height, AnchorPos anchor)
+      : left = _leftOffset(width, anchor),
+        top = _topOffset(width, anchor);
+
+  static double _leftOffset(double width, AnchorPos anchor) {
+    switch (anchor) {
+      case AnchorPos.left:
+        return 0.0;
+      case AnchorPos.right:
+        return width;
+      case AnchorPos.top:
+      case AnchorPos.bottom:
+      case AnchorPos.center:
+      default:
+        return width / 2;
+    }
+  }
+
+  static double _topOffset(double height, AnchorPos anchor) {
+    switch (anchor) {
+      case AnchorPos.top:
+        return 0.0;
+      case AnchorPos.bottom:
+        return height;
+      case AnchorPos.left:
+      case AnchorPos.right:
+      case AnchorPos.center:
+      default:
+        return height / 2;
+    }
+  }
+}
+
+enum AnchorPos {
+  left,
+  right,
+  top,
+  bottom,
+  center,
+}
+
 class Marker {
   final LatLng point;
   final WidgetBuilder builder;
   final double width;
   final double height;
-  final List<double> anchor;
+  final Anchor _anchor;
+
   Marker({
     this.point,
     this.builder,
     this.width = 30.0,
     this.height = 30.0,
-    this.anchor = const [15.0, 15.0]
-  });
+    AnchorPos anchor,
+    Anchor anchorOverride,
+  }) : this._anchor =
+            anchorOverride ?? new Anchor._(width, height, anchor);
 }
 
 class MarkerLayer extends StatelessWidget {
@@ -42,8 +92,10 @@ class MarkerLayer extends StatelessWidget {
             new Positioned(
               width: markerOpt.width,
               height: markerOpt.height,
-              left: (pos.x - (markerOpt.width - markerOpt.anchor[0])).toDouble(),
-              top: (pos.y - (markerOpt.height - markerOpt.anchor[1])).toDouble(),
+              left: (pos.x - (markerOpt.width - markerOpt._anchor.left))
+                  .toDouble(),
+              top: (pos.y - (markerOpt.height - markerOpt._anchor.top))
+                  .toDouble(),
               child: markerOpt.builder(context),
             ),
           );

flutter_map_example/flutter_map_example.iml

@@ -3,6 +3,7 @@
   <component name="NewModuleRootManager" inherit-compiler-output="true">
     <exclude-output />
     <content url="file://$MODULE_DIR$">
+      <excludeFolder url="file://$MODULE_DIR$/.dart_tool" />
       <excludeFolder url="file://$MODULE_DIR$/.pub" />
       <excludeFolder url="file://$MODULE_DIR$/build" />
       <excludeFolder url="file://$MODULE_DIR$/../leaflet_flutter_example/.pub" />