Time for action – functionality of a tic-tac-toe board

We need to implement a function that will be called upon by clicking on any of the nine buttons on the board. It has to change the text of the button that was clicked on—either X or O—based on which player made the move; then, it has to check whether the move resulted in winning the game by the player (or a draw if no more moves are possible), and if the game ended, it should emit an appropriate signal, informing the environment about the event.

When the user clicks on a button, the clicked() signal is emitted. Connecting this signal to a custom slot lets us implement the mentioned functionality, but since the signal doesn't carry any parameters, how do we tell which button caused the slot to be triggered? We could connect each button to a separate slot but that's an ugly solution. Fortunately, there are two ways of working around this problem. When a slot is invoked, a pointer to the object that caused the signal to be sent is accessible...