simple_chess_board 1.3.0

A simple chess board widget which do not handle game state, but with several options for board orientation, adding arrows, and others.

A simple chess board widget, with several options.

Features

A simple chess board, where:

• you can configure the current position,
• you can configure each side type (e.g : we can drag pieces for white side, but block them for black side if we want to make an external engine move),
• you can show coordinates and player turn around the board,
• you define your own widget for processing with promotion piece selection,
• you can choose the orientation of the board (are Blacks at bottom ?),
• you can add arrows,
• you can choose colors,
• the common size will be the least of attributed width/height : if width > height => takes the allocated height, and the reverse if width < height (so for example, if you use it in a Row/Column, you can set the stretch alignment in the cross axis direction for a quite good layout/effect).

If you want to implement game logic, you can use the chess package.

Please, also notice, that when there is a pending promotion, you should prevent the user to reverse the board orientation. Otherwise the result can be quite ugly. This can easily be done by showing a modal over your interface when the user is invited to choose a promotion piece.

Getting started

To use SimpleChessBoard widget, add simple_chess_board as a dependency in your pubspec.yaml .

Usage

You can find a longer example in the example folder.

There's also a live example on Zap.

Simple example

SimpleChessBoard(
    engineThinking: false,
    fen: '8/8/8/4p1K1/2k1P3/8/8/8 b - - 0 1',
    onMove: ({required ShortMove move}){
        print('${move.from}|${move.to}|${move.promotion}')
    },
    orientation: BoardColor.black,
    whitePlayerType: PlayerType.human,
    blackPlayerType: PlayerType.computer,
    lastMoveToHighlight: BoardArrow(from: 'e2', to: 'e4', color: Colors.blueAccent),
    onPromote: () => PieceType.queen,
),

Handling promotion

You handle promotion in the function you give to the mandatory onPromote parameter. In this function you return the PieceType you want to use.

As an example:

SimpleChessBoard(
    engineThinking: false,
    fen: '1k6/p2KP3/1p6/8/4B3/8/8/8 w - - 0 1',
    onMove: ({required ShortMove move}){
        print('${move.from}|${move.to}|${move.promotion}')
    },
    orientation: BoardColor.white,
    whitePlayerType: PlayerType.human,
    blackPlayerType: PlayerType.computer,
    lastMoveToHighlight: BoardArrow(from: 'e2', to: 'e4', color: Colors.blueAccent),
        onPromote: () {
            return showDialog<PieceType>(
            context: context,
            builder: (_) {
                return AlertDialog(
                title: Text('Promotion'),
                content: Column(
                    mainAxisSize: MainAxisSize.min,
                    children: [
                            ListTile(
                                title: Text("Queen"),
                                onTap: () => navigator.pop(PieceType.queen),
                            ),
                            ListTile(
                                title: Text("Rook"),
                                onTap: () => navigator.pop(PieceType.rook),
                            ),
                            ListTile(
                                title: Text("Bishop"),
                                onTap: () => navigator.pop(PieceType.bishop),
                            ),
                            ListTile(
                                title: Text("Knight"),
                                onTap: () => navigator.pop(PieceType.knight),
                            ),
                        ],
                    ),
                );
            },
        );
    },
)

Parameters

• fen : board position in Forsyth-Edwards Notation. Example : rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1.
• orientation: says if Black side is at bottom or not. Give BoardColor.black if Blacks must be at bottom of the board, or BoardColor.white otherwise.
• whitePlayerType : if it is white turn and this is set to PlayerType.human, then the user will be able to move pieces. Either with the click method, or with the drag and drop method. Otherwise, if set to PlayerType.computer and it is white turn, then the user won't be able to move pieces.
• blackPlayerType : if it is black turn and this is set to PlayerType.human, then the user will be able to move pieces. Either with the click method, or with the drag and drop method. Otherwise, if set to PlayerType.computer and it is black turn, then the user won't be able to move pieces.
• onMove : the given function will be called whenever a move is done on board by the user (if he's allowed to move pieces). It has a single required parameter ShortMove move which carries data about from/to cells, as well as promotion type which is nullable. Notice that it's up to you to update the board or not based on the move you receive from this function. You can use the chess package to get the new position.
• onPromote: the given function is called whenever a promotion move is done on board by the user (if he's allowed to move pieces). You must return a Future<PieceType?>. The Future can wrap a null value in order to cancel. Otherwise, wrap a PieceType such as PieceType.queen.
• showCoordinatesZone (optionnal) : says if you want to show coordinates and player turn around the board. Give true for showing it, or false for removing it.
• lastMoveToHighlight (optionnal) : give data about the arrow to draw on the board, if any. You pass a BoardArrow with from/to cells String and color Color (such as BoardArrow(from: 'e2', to: 'e4', color: Colors.blueAccent)) if you want to draw an arrow, or null if you don't want any arrow on the board.
• engineThinking (optionnal) : says if you want to show a CircularProgressBar in order to indicate that an engine is trying to compute next move for example.

Project's repository

You can find the repository on Github.

Credits

• Using code from Flutter Chess board.
• Using code from Flutter Stateless Chess board.
• Using chess pieces definitions from Wikimedia Commons.