first!

you should drag the king to the position where it will end up after castling.
If it doesn't work, that means you can't castle

Yeah as bastiaan says just move the king to where you want it to end up.

Remember you can't castle through check while in check or if the king/rook has already moved

thanks bastiaan.many many thanks.

bastiaan wrote:

you should drag the king to the position where it will end up after castling.
If it doesn't work, that means you can't castle

Just don't drag the rook instead, or you lose the opportunity to castle with that rook(and waste a move possible even hanging a pawn).

thank you very much