Fix 1-pixel lines between squares

In window widths or heigths that are not divisible by 8, the chess board
would contain lines between the squares (since the contraints of the
chess board rows would contain non-integer constraints).

With this commit, we calculate margins manually, in order to constrict
the chess board to widths and heights that are divisible by 8.

lib/chess/chess_board.dart

@@ -1,4 +1,5 @@
 import 'dart:developer';
+import 'dart:math' as math;
 
 import 'package:flutter/material.dart';
 import 'package:mchess/chess_bloc/chess_bloc.dart';
@@ -42,11 +43,36 @@ class ChessBoard extends StatelessWidget {
   Widget build(BuildContext context) {
     log("ChessBoard's build()");
 
+    return LayoutBuilder(builder: (context, constraints) {
+      /*We calculate the margins manually, because otherwise we would have 
+      lines that are 1 pixel wide between the squares (which is ugly)*/
+      int smallerSize =
+          math.min(constraints.maxWidth.toInt(), constraints.maxHeight.toInt());
+      int desiredSize = smallerSize - smallerSize % 8;
+      int verticalMargin = constraints.maxHeight.toInt() - desiredSize;
+      int verticalMarginTop = verticalMargin ~/ 2;
+      int verticalMarginBottom = verticalMargin - verticalMarginTop;
+      int horizontalMargin = constraints.maxWidth.toInt() - desiredSize;
+      int horizontalMarginLeft = horizontalMargin ~/ 2;
+      int horizontalMarginRight = horizontalMargin - horizontalMarginLeft;
       return Container(
-      decoration: const BoxDecoration(
+        margin: EdgeInsets.only(
-          boxShadow: [BoxShadow(color: Colors.black, offset: Offset(10, 10))]),
+          left: horizontalMarginLeft.toDouble(),
+          right: horizontalMarginRight.toDouble(),
+          top: verticalMarginTop.toDouble(),
+          bottom: verticalMarginBottom.toDouble(),
+        ),
+        child: FittedBox(
+          fit: BoxFit.contain,
+          child: Container(
+            decoration: const BoxDecoration(boxShadow: [
+              BoxShadow(color: Colors.black, offset: Offset(10, 10))
+            ]),
             child: _buildBoard(bState.bottomColor == ChessColor.black),
+          ),
+        ),
       );
+    });
   }
 
   Row _buildChessRow(int rowNo, bool flipped) {

lib/pages/chess_game.dart

@@ -1,15 +1,12 @@
-import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:go_router/go_router.dart';
 import 'package:mchess/chess_bloc/chess_bloc.dart';
 
 import 'package:mchess/chess/chess_board.dart';
-import 'package:mchess/chess/turn_indicator_widget.dart';
 import 'package:mchess/chess_bloc/promotion_bloc.dart';
 import 'package:mchess/utils/chess_utils.dart';
 import 'package:mchess/utils/widgets/promotion_dialog.dart';
-import 'package:mchess/utils/widgets/server_log_widget.dart';
 import 'package:uuid/uuid.dart';
 
 class ChessGame extends StatefulWidget {
@@ -36,13 +33,8 @@ class _ChessGameState extends State<ChessGame> {
   Widget build(BuildContext context) {
     return Scaffold(
       body: Center(
-        child: FittedBox(
+        child: Container(
-          fit: BoxFit.contain,
+          margin: const EdgeInsets.all(10),
-          child: Column(
-            children: [
-              if (kDebugMode) const ServerLogWidget(textColor: Colors.white),
-              Container(
-                margin: const EdgeInsets.all(20),
           child: BlocListener<PromotionBloc, PromotionState>(
             listener: (context, state) {
               if (state.showPromotionDialog) {
@@ -58,10 +50,6 @@ class _ChessGameState extends State<ChessGame> {
             ),
           ),
         ),
-              if (kDebugMode) const TurnIndicator(),
-            ],
-          ),
-        ),
       ),
       floatingActionButton: FloatingActionButton(
         onPressed: () {