tictactoe.cpp Example File
^{designer/taskmenuextension/tictactoe.cpp}

    /****************************************************************************
    **
    ** Copyright (C) 2005-2006 Trolltech ASA. All rights reserved.
    **
    ** This file is part of the documentation of the Qt Toolkit.
    **
    ** This file may be used under the terms of the GNU General Public
    ** License version 2.0 as published by the Free Software Foundation
    ** and appearing in the file LICENSE.GPL included in the packaging of
    ** this file.  Please review the following information to ensure GNU
    ** General Public Licensing requirements will be met:
    ** http://www.trolltech.com/products/qt/opensource.html
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    ** review the following information:
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    ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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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;
        for (int position = 0; position < 9; ++position) {
            if (newState.at(position) != Empty)
                ++turnNumber;
        }
        myState = newState;
        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 *)
    {
        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);
    }