tictactoe.cpp Example File

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 #include <QtGui>

 #include "tictactoe.h"

 TicTacToe::TicTacToe(QWidget *parent)
     : QWidget(parent)
 {
 }

 QSize TicTacToe::minimumSizeHint() const
 {
     return QSize(200, 200);
 }

 QSize TicTacToe::sizeHint() const
 {
     return QSize(200, 200);
 }

 void TicTacToe::setState(const QString &newState)
 {
     turnNumber = 0;
     myState = "---------";
     int position = 0;
     while (position < 9 && position < newState.length()) {
         QChar mark = newState.at(position);
         if (mark == Cross || mark == Nought) {
             ++turnNumber;
             myState.replace(position, 1, mark);
         }
         position++;
     }
     update();
 }

 QString TicTacToe::state() const
 {
     return myState;
 }

 void TicTacToe::clearBoard()
 {
     myState = "---------";
     turnNumber = 0;
     update();
 }

 void TicTacToe::mousePressEvent(QMouseEvent *event)
 {
     if (turnNumber == 9) {
         clearBoard();
         update();
     } else {
         for (int position = 0; position < 9; ++position) {
             QRect cell = cellRect(position / 3, position % 3);
             if (cell.contains(event->pos())) {
                 if (myState.at(position) == Empty) {
                     if (turnNumber % 2 == 0)
                         myState.replace(position, 1, Cross);
                     else
                         myState.replace(position, 1, Nought);
                     ++turnNumber;
                     update();
                 }
             }
         }
     }
 }

 void TicTacToe::paintEvent(QPaintEvent * /* event */)
 {
     QPainter painter(this);
     painter.setRenderHint(QPainter::Antialiasing);

     painter.setPen(QPen(Qt::darkGreen, 1));
     painter.drawLine(cellWidth(), 0, cellWidth(), height());
     painter.drawLine(2 * cellWidth(), 0, 2 * cellWidth(), height());
     painter.drawLine(0, cellHeight(), width(), cellHeight());
     painter.drawLine(0, 2 * cellHeight(), width(), 2 * cellHeight());

     painter.setPen(QPen(Qt::darkBlue, 2));

     for (int position = 0; position < 9; ++position) {
         QRect cell = cellRect(position / 3, position % 3);

         if (myState.at(position) == Cross) {
             painter.drawLine(cell.topLeft(), cell.bottomRight());
             painter.drawLine(cell.topRight(), cell.bottomLeft());
         } else if (myState.at(position) == Nought) {
             painter.drawEllipse(cell);
         }
     }

     painter.setPen(QPen(Qt::yellow, 3));

     for (int position = 0; position < 9; position = position + 3) {
         if (myState.at(position) != Empty
                 && myState.at(position + 1) == myState.at(position)
                 && myState.at(position + 2) == myState.at(position)) {
             int y = cellRect((position / 3), 0).center().y();
             painter.drawLine(0, y, width(), y);
             turnNumber = 9;
         }
     }

     for (int position = 0; position < 3; ++position) {
         if (myState.at(position) != Empty
                 && myState.at(position + 3) == myState.at(position)
                 && myState.at(position + 6) == myState.at(position)) {
             int x = cellRect(0, position).center().x();
             painter.drawLine(x, 0, x, height());
             turnNumber = 9;
         }
     }
     if (myState.at(0) != Empty && myState.at(4) == myState.at(0)
             && myState.at(8) == myState.at(0)) {
         painter.drawLine(0, 0, width(), height());
         turnNumber = 9;
     }
     if (myState.at(2) != Empty && myState.at(4) == myState.at(2)
             && myState.at(6) == myState.at(2)) {
         painter.drawLine(0, height(), width(), 0);
         turnNumber = 9;
     }
 }

 QRect TicTacToe::cellRect(int row, int column) const
 {
     const int HMargin = width() / 30;
     const int VMargin = height() / 30;
     return QRect(column * cellWidth() + HMargin,
                  row * cellHeight() + VMargin,
                  cellWidth() - 2 * HMargin,
                  cellHeight() - 2 * VMargin);
 }