Clicking King then clicking Rook should not castle

[hendley]

This is very unexpected and I have been burned by it many times.

There are many situations when I click / pick up my King to castle, then see that it is either bad to castle, or much better to move my rook, so I click / pick up my Rook instead, only to inadvertently castle!

I should only be able to castle by dragging my King to the destination square, or by clicking my King and then clicking the destination square.

[ornicar]

it's required for chess960.

[Happy0]

Perhaps at least some sort of visual hint could be added to indicate that clicking on the castle while the king is selected will result in castling.

[Unihedro]

@Happy0: There already is. The castle-able rook gets hover feedback when the king is selected or held.

[Unihedro]

linked #839