Adding NineTileBox widget

lib/widgets/nine_tile_box.dart

@@ -0,0 +1,138 @@
+import 'package:flutter/widgets.dart' as widgets;
+import 'package:meta/meta.dart';
+import '../sprite.dart';
+import 'dart:ui';
+
+class _Painter extends widgets.CustomPainter {
+  final Image image;
+  final double tileSize;
+  final double destTileSize;
+
+  _Painter(
+      {@required this.image,
+      @required this.tileSize,
+      @required this.destTileSize});
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    final topLeftCorner =
+        Sprite.fromImage(image, x: 0, y: 0, width: tileSize, height: tileSize);
+    final topRightCorner = Sprite.fromImage(image,
+        x: tileSize * 2, y: 0, width: tileSize, height: tileSize);
+
+    final bottomLeftCorner = Sprite.fromImage(image,
+        x: 0, y: 2 * tileSize, width: tileSize, height: tileSize);
+    final bottomRightCorner = Sprite.fromImage(image,
+        x: tileSize * 2, y: 2 * tileSize, width: tileSize, height: tileSize);
+
+    final topSide = Sprite.fromImage(image,
+        x: tileSize, y: 0, width: tileSize, height: tileSize);
+    final bottomSide = Sprite.fromImage(image,
+        x: tileSize, y: tileSize * 2, width: tileSize, height: tileSize);
+
+    final leftSide = Sprite.fromImage(image,
+        x: 0, y: tileSize, width: tileSize, height: tileSize);
+    final rightSide = Sprite.fromImage(image,
+        x: tileSize * 2, y: tileSize, width: tileSize, height: tileSize);
+
+    final middle = Sprite.fromImage(image,
+        x: tileSize, y: tileSize, width: tileSize, height: tileSize);
+
+    // Middle
+    for (var y = destTileSize;
+        y < size.height - destTileSize;
+        y = y + destTileSize) {
+      for (var x = destTileSize;
+          x < size.width - destTileSize;
+          x = x + destTileSize) {
+        middle.renderRect(
+            canvas, Rect.fromLTWH(x, y, destTileSize, destTileSize));
+      }
+    }
+
+    // Top and bottom side
+    for (var i = destTileSize;
+        i < size.width - destTileSize;
+        i = i + destTileSize) {
+      topSide.renderRect(
+          canvas, Rect.fromLTWH(i, 0, destTileSize, destTileSize));
+      bottomSide.renderRect(
+          canvas,
+          Rect.fromLTWH(
+              i, size.height - destTileSize, destTileSize, destTileSize));
+    }
+
+    // Left and right side
+    for (var i = destTileSize;
+        i < size.height - destTileSize;
+        i = i + destTileSize) {
+      leftSide.renderRect(
+          canvas, Rect.fromLTWH(0, i, destTileSize, destTileSize));
+      rightSide.renderRect(
+          canvas,
+          Rect.fromLTWH(
+              size.width - destTileSize, i, destTileSize, destTileSize));
+    }
+
+    // Corners
+    topLeftCorner.renderRect(
+        canvas, Rect.fromLTWH(0, 0, destTileSize, destTileSize));
+    topRightCorner.renderRect(
+        canvas,
+        Rect.fromLTWH(
+            size.width - destTileSize, 0, destTileSize, destTileSize));
+
+    bottomLeftCorner.renderRect(
+        canvas,
+        Rect.fromLTWH(
+            0, size.height - destTileSize, destTileSize, destTileSize));
+    bottomRightCorner.renderRect(
+        canvas,
+        Rect.fromLTWH(size.width - destTileSize, size.height - destTileSize,
+            destTileSize, destTileSize));
+  }
+
+  @override
+  bool shouldRepaint(_) => false;
+}
+
+class NineTileBox extends widgets.StatelessWidget {
+  final Image image;
+  final double tileSize;
+  final double destTileSize;
+  final double width;
+  final double height;
+
+  final widgets.Widget child;
+
+  final widgets.EdgeInsetsGeometry padding;
+
+  NineTileBox({
+    @required this.image,
+    @required this.tileSize,
+    @required this.destTileSize,
+    this.child,
+    this.width,
+    this.height,
+    this.padding,
+  });
+
+  @override
+  widgets.Widget build(widgets.BuildContext context) {
+    return widgets.Container(
+      width: width,
+      height: height,
+      child: widgets.CustomPaint(
+        painter: _Painter(
+          image: image,
+          tileSize: tileSize,
+          destTileSize: destTileSize,
+        ),
+        child: widgets.Container(
+          child: child,
+          padding: padding,
+        ),
+      ),
+    );
+  }
+}