Premoves

[zarinda]

Hello, this is good chess board, but I can not use premoves, for example I play with white pieces and I do a move and my pieces to disable it is good, But when my opponent thinking I want to do a premove but I do not how can I do it, so it is very important tool because in blitzkrieg game when play in 2 or 3 minutes this tool is very important.

[mganjoo]

Hi, thanks for checking out the library!

Pre-moves are a good application, but I do not have plans to add it to the core library as that involves state management, and this chessboard is not intended to maintain complex internal state.

However, I think it should be possible to implement pre-moves in your application using this library, assuming you manage state yourself in your application. Here's a potential way to do it:

(Assuming Player A = white, Player B = black)

• Start with turn = white (Player A). When Player A makes a move, then update your copy of the game state (FEN) accordingly. It is now Player B's turn to make a move.
• On Player B's board, set turn = black, so that Player B can make a move freely.
• On Player A's board, set turn = white, so that Player A can also move. This isn't a real move, though - just a pre-move. You can customize styles so that moves appear in a different color. A detailed set of CSS styling properties is available on the API page.

Now, you have to handle two different events (you can use a combination of movestart or movefinished for this - details on API page):

• For Player A (the person who can pre-move): when they move a piece, record the move in your application state, and also update board FEN for player A to reflect this move (we will revert this after Player B makes a move). Style board accordingly so that Player A knows that this is just a pre-move.
• For Player B (the person whose turn it is), when they move a piece, update board FEN for Player A.
• Immediately after that (or after a short delay), check if recorded move from Player A is valid:
• If the pre-move was valid, update game FEN again. Use this new FEN to change board display for both Player A and B. It is now B's turn again, so set turn = black.
• If the pre-move was not valid, then don't change the game FEN any further. Use the existing FEN to override board display for Player A, since their pre-move was ignored. Now it is Player A's turn, so set turn = white.

Let me know if the above makes sense! Closing issue.