Center label for polygons

lib/src/layer/polygon_layer.dart

@@ -1,6 +1,7 @@
 import 'dart:math';
 import 'dart:ui';
 
+import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_map/flutter_map.dart';
 import 'package:flutter_map/src/map/map.dart';
@@ -35,6 +36,8 @@ class Polygon {
  final Color borderColor;
  final bool disableHolesBorder;
  final bool isDotted;
+ final String label;
+ final TextStyle labelStyle;
  LatLngBounds boundingBox;
 
  Polygon({
@@ -45,9 +48,9 @@ class Polygon {
  this.borderColor = const Color(0xFFFFFF00),
  this.disableHolesBorder = false,
  this.isDotted = false,
- }) : holeOffsetsList = null == holePointsList || holePointsList.isEmpty
-  ? null
-   : List.generate(holePointsList.length, (_) => []);
+  this.label,
+ this.labelStyle = const TextStyle(),
+ }) : holeOffsetsList = null == holePointsList || holePointsList.isEmpty ? null : List.generate(holePointsList.length, (_) => []);
 }
 
 class PolygonLayerWidget extends StatelessWidget {
@@ -66,8 +69,7 @@ class PolygonLayer extends StatelessWidget {
  final MapState map;
  final Stream stream;
 
- PolygonLayer(this.polygonOpts, this.map, this.stream)
- : super(key: polygonOpts.key);
+ PolygonLayer(this.polygonOpts, this.map, this.stream) : super(key: polygonOpts.key);
 
  @override
  Widget build(BuildContext context) {
@@ -95,8 +97,7 @@ class PolygonLayer extends StatelessWidget {
  }
  }
 
- if (polygonOpts.polygonCulling &&
- !polygon.boundingBox.isOverlapping(map.bounds)) {
+ if (polygonOpts.polygonCulling && !polygon.boundingBox.isOverlapping(map.bounds)) {
  // skip this polygon as it's offscreen
  continue;
  }
@@ -105,11 +106,9 @@ class PolygonLayer extends StatelessWidget {
 
  if (null != polygon.holePointsList) {
  for (var i = 0, len = polygon.holePointsList.length; i < len; ++i) {
- _fillOffsets(
- polygon.holeOffsetsList[i], polygon.holePointsList[i]);
+ _fillOffsets(polygon.holeOffsetsList[i], polygon.holePointsList[i]);
  }
  }
-
  polygons.add(
  CustomPaint(
  painter: PolygonPainter(polygon),
@@ -132,8 +131,7 @@ class PolygonLayer extends StatelessWidget {
  var point = points[i];
 
  var pos = map.project(point);
- pos = pos.multiplyBy(map.getZoomScale(map.zoom, map.zoom)) -
- map.getPixelOrigin();
+ pos = pos.multiplyBy(map.getZoomScale(map.zoom, map.zoom)) - map.getPixelOrigin();
  offsets.add(Offset(pos.x.toDouble(), pos.y.toDouble()));
  if (i > 0) {
  offsets.add(Offset(pos.x.toDouble(), pos.y.toDouble()));
@@ -166,21 +164,17 @@ class PolygonPainter extends CustomPainter {
 
  if (polygonOpt.isDotted) {
  var spacing = polygonOpt.borderStrokeWidth * 1.5;
- _paintDottedLine(
- canvas, polygonOpt.offsets, borderRadius, spacing, borderPaint);
+ _paintDottedLine(canvas, polygonOpt.offsets, borderRadius, spacing, borderPaint);
 
- if (!polygonOpt.disableHolesBorder &&
- null != polygonOpt.holeOffsetsList) {
+ if (!polygonOpt.disableHolesBorder && null != polygonOpt.holeOffsetsList) {
  for (var offsets in polygonOpt.holeOffsetsList) {
- _paintDottedLine(
- canvas, offsets, borderRadius, spacing, borderPaint);
+ _paintDottedLine(canvas, offsets, borderRadius, spacing, borderPaint);
  }
  }
  } else {
  _paintLine(canvas, polygonOpt.offsets, borderRadius, borderPaint);
 
- if (!polygonOpt.disableHolesBorder &&
- null != polygonOpt.holeOffsetsList) {
+ if (!polygonOpt.disableHolesBorder && null != polygonOpt.holeOffsetsList) {
  for (var offsets in polygonOpt.holeOffsetsList) {
  _paintLine(canvas, offsets, borderRadius, borderPaint);
  }
@@ -189,8 +183,7 @@ class PolygonPainter extends CustomPainter {
  }
  }
 
- void _paintDottedLine(Canvas canvas, List<Offset> offsets, double radius,
- double stepLength, Paint paint) {
+ void _paintDottedLine(Canvas canvas, List<Offset> offsets, double radius, double stepLength, Paint paint) {
  var startDistance = 0.0;
  for (var i = 0; i < offsets.length - 1; i++) {
  var o0 = offsets[i];
@@ -204,15 +197,12 @@ class PolygonPainter extends CustomPainter {
  canvas.drawCircle(offset, radius, paint);
  distance += stepLength;
  }
- startDistance = distance < totalDistance
- ? stepLength - (totalDistance - distance)
- : distance - totalDistance;
+ startDistance = distance < totalDistance ? stepLength - (totalDistance - distance) : distance - totalDistance;
  }
  canvas.drawCircle(offsets.last, radius, paint);
  }
 
- void _paintLine(
- Canvas canvas, List<Offset> offsets, double radius, Paint paint) {
+ void _paintLine(Canvas canvas, List<Offset> offsets, double radius, Paint paint) {
  canvas.drawPoints(PointMode.lines, [...offsets, offsets[0]], paint);
  for (var offset in offsets) {
  canvas.drawCircle(offset, radius, paint);
@@ -239,9 +229,10 @@ class PolygonPainter extends CustomPainter {
  var path = Path();
  path.addPolygon(polygonOpt.offsets, true);
  canvas.drawPath(path, paint);
-
+ if (polygonOpt.label != null) {
+ _paintText(canvas, polygonOpt.offsets);
+ }
  _paintBorder(canvas);
-
  canvas.restore();
  } else {
  canvas.clipRect(rect);
@@ -250,13 +241,35 @@ class PolygonPainter extends CustomPainter {
  ..color = polygonOpt.color;
 
  var path = Path();
+
  path.addPolygon(polygonOpt.offsets, true);
  canvas.drawPath(path, paint);
-
+ if (polygonOpt.label != null) {
+ _paintText(canvas, polygonOpt.offsets);
+ }
  _paintBorder(canvas);
  }
  }
 
+ void _paintText(Canvas canvas, List<Offset> points) {
+ var dx = points.map((e) => e.dx).toList().fold(0.0, (previousValue, element) => previousValue + element) / points.length;
+ var dy = points.map((e) => e.dy).toList().fold(0.0, (previousValue, element) => previousValue + element) / points.length;
+
+ final textSpan = TextSpan(text: polygonOpt.label, style: polygonOpt.labelStyle);
+ final textPainter = TextPainter(
+ text: textSpan,
+ textAlign: TextAlign.center,
+ textDirection: TextDirection.ltr,
+ );
+ textPainter.layout(minWidth: 0, maxWidth: dx);
+ dx = dx - textPainter.width / 2;
+
+ textPainter.paint(
+ canvas,
+ Offset(dx, dy),
+ );
+ }
+
  @override
  bool shouldRepaint(PolygonPainter other) => false;