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#ifndef M_PI

#define M_PI 3.14159265358979323846

#endif

#define WORLD_SIZE 8

int world_map[WORLD_SIZE][WORLD_SIZE] = {

    { 1, 1, 1, 1, 6, 1, 1, 1 },

    { 1, 0, 0, 1, 0, 0, 0, 7 },

    { 1, 1, 0, 1, 0, 1, 1, 1 },

    { 6, 0, 0, 0, 0, 0, 0, 3 },

    { 1, 8, 8, 0, 8, 0, 8, 1 },

    { 2, 2, 0, 0, 8, 8, 7, 1 },

    { 3, 0, 0, 0, 0, 0, 0, 5 },

    { 2, 2, 2, 2, 7, 4, 4, 4 },

};

#define TEXTURE_SIZE 64

#define TEXTURE_BLOCK (TEXTURE_SIZE * TEXTURE_SIZE)

            : QWidget(parent)

            , angle(0.5)

            , playerPos(1.5, 1.5)

            , angleDelta(0)

            , moveDelta(0)

            , touchDevice(false) {

        // http://www.areyep.com/RIPandMCS-TextureLibrary.html

        textureImg.load(":/textures.png");

        textureImg = textureImg.convertToFormat(QImage::Format_ARGB32);

        Q_ASSERT(textureImg.width() == TEXTURE_SIZE * 2);

        Q_ASSERT(textureImg.bytesPerLine() == 4 * TEXTURE_SIZE * 2);

        textureCount = textureImg.height() / TEXTURE_SIZE;

        watch.start();

        ticker.start(25, this);

        setAttribute(Qt::WA_OpaquePaintEvent, true);

        setMouseTracking(false);

    }

        int interval = qBound(20, watch.elapsed(), 250);

        watch.start();

        angle += angleDelta * interval / 1000;

        qreal step = moveDelta * interval / 1000;

        qreal dx = cos(angle) * step;

        qreal dy = sin(angle) * step;

        QPointF pos = playerPos + 3 * QPointF(dx, dy);

        int xi = static_cast<int>(pos.x());

        int yi = static_cast<int>(pos.y());

        if (world_map[yi][xi] == 0)

            playerPos = playerPos + QPointF(dx, dy);

    }

        static QTime frameTick;

        static int totalFrame = 0;

        if (!(totalFrame & 31)) {

            int elapsed = frameTick.elapsed();

            frameTick.start();

            int fps = 32 * 1000 / (1 + elapsed);

            setWindowTitle(QString("Raycasting (%1 FPS)").arg(fps));

        }

        totalFrame++;

    }

        // setup the screen surface

        if (buffer.size() != bufferSize)

            buffer = QImage(bufferSize, QImage::Format_ARGB32);

        int bufw = buffer.width();

        int bufh = buffer.height();

        if (bufw <= 0 || bufh <= 0)

            return;

        // we intentionally cheat here, to avoid detach

        const uchar *ptr = buffer.bits();

        QRgb *start = (QRgb*)(ptr);

        QRgb stride = buffer.bytesPerLine() / 4;

        QRgb *finish = start + stride * bufh;

        // prepare the texture pointer

        const uchar *src = textureImg.bits();

        const QRgb *texsrc = reinterpret_cast<const QRgb*>(src);

        // cast all rays here

        qreal sina = sin(angle);

        qreal cosa = cos(angle);

        qreal u = cosa - sina;

        qreal v = sina + cosa;

        qreal du = 2 * sina / bufw;

        qreal dv = -2 * cosa / bufw;

        for (int ray = 0; ray < bufw; ++ray, u += du, v += dv) {

            // everytime this ray advances 'u' units in x direction,

            // it also advanced 'v' units in y direction

            qreal uu = (u < 0) ? -u : u;

            qreal vv = (v < 0) ? -v : v;

            qreal duu = 1 / uu;

            qreal dvv = 1 / vv;

            int stepx = (u < 0) ? -1 : 1;

            int stepy = (v < 0) ? -1 : 1;

            // the cell in the map that we need to check

            qreal px = playerPos.x();

            qreal py = playerPos.y();

            int mapx = static_cast<int>(px);

            int mapy = static_cast<int>(py);

            // the position and texture for the hit

            int texture = 0;

            qreal hitdist = 0.1;

            qreal texofs = 0;

            bool dark = false;

            // first hit at constant x and constant y lines

            qreal distx = (u > 0) ? (mapx + 1 - px) * duu : (px - mapx) * duu;

            qreal disty = (v > 0) ? (mapy + 1 - py) * dvv : (py - mapy) * dvv;

            // loop until we hit something

            while (texture <= 0) {

                if (distx > disty) {

                    // shorter distance to a hit in constant y line

                    hitdist = disty;

                    disty += dvv;

                    mapy += stepy;

                    texture = world_map[mapy][mapx];

                    if (texture > 0) {

                        dark = true;

                        if (stepy > 0) {

                            qreal ofs = px + u * (mapy - py) / v;

                            texofs = ofs - floor(ofs);

                        } else {

                            qreal ofs = px + u * (mapy + 1 - py) / v;

                            texofs = ofs - floor(ofs);

                        }

                    }

                } else {

                    // shorter distance to a hit in constant x line

                    hitdist = distx;

                    distx += duu;

                    mapx += stepx;

                    texture = world_map[mapy][mapx];

                    if (texture > 0) {

                        if (stepx > 0) {

                            qreal ofs = py + v * (mapx - px) / u;

                            texofs = ofs - floor(ofs);

                        } else {

                            qreal ofs = py + v * (mapx + 1 - px) / u;

                            texofs = ceil(ofs) - ofs;

                        }

                    }

                }

            }

            // get the texture, note that the texture image

            // has two textures horizontally, "normal" vs "dark"

            int col = static_cast<int>(texofs * TEXTURE_SIZE);

            col = qBound(0, col, TEXTURE_SIZE - 1);

            texture = (texture - 1) % textureCount;

            const QRgb *tex = texsrc + TEXTURE_BLOCK * texture * 2 +

                              (TEXTURE_SIZE * 2 * col);

            if (dark)

                tex += TEXTURE_SIZE;

            // start from the texture center (horizontally)

            int h = static_cast<int>(bufw / hitdist / 2);

            int dy = (TEXTURE_SIZE << 12) / h;

            int p1 = ((TEXTURE_SIZE / 2) << 12) - dy;

            int p2 = p1 + dy;

            // start from the screen center (vertically)

            // y1 will go up (decrease), y2 will go down (increase)

            int y1 = bufh / 2;

            int y2 = y1 + 1;

            QRgb *pixel1 = start + y1 * stride + ray;

            QRgb *pixel2 = pixel1 + stride;

            // map the texture to the sliver

            while (y1 >= 0 && y2 < bufh && p1 >= 0) {

                *pixel1 = tex[p1 >> 12];

                *pixel2 = tex[p2 >> 12];

                p1 -= dy;

                p2 += dy;

                --y1;

                ++y2;

                pixel1 -= stride;

                pixel2 += stride;

            }

            // ceiling and floor

            for (; pixel1 > start; pixel1 -= stride)

                *pixel1 = qRgb(0, 0, 0);

            for (; pixel2 < finish; pixel2 += stride)

                *pixel2 = qRgb(96, 96, 96);

        }

        update(QRect(QPoint(0, 0), bufferSize));

    }

#if defined(Q_OS_WINCE_WM)

        touchDevice = true;

#elif defined(Q_OS_SYMBIAN)

        // FIXME: use HAL

        if (width() > 480 || height() > 480)

            touchDevice = true;

#else

        touchDevice = false;

#endif

        if (touchDevice) {

            if (width() < height()) {

                trackPad = QRect(0, height() / 2, width(), height() / 2);

                centerPad = QPoint(width() / 2, height() * 3 / 4);

                bufferSize = QSize(width(), height() / 2);

            } else {

                trackPad = QRect(width() / 2, 0, width() / 2, height());

                centerPad = QPoint(width() * 3 / 4, height() / 2);

                bufferSize = QSize(width() / 2, height());

            }

        } else {

            trackPad = QRect();

            bufferSize = size();

        }

        update();

   }

        updatePlayer();

        render();

        showFps();

    }

        QPainter p(this);

        p.setCompositionMode(QPainter::CompositionMode_Source);

        p.drawImage(event->rect(), buffer, event->rect());

        if (touchDevice && event->rect().intersects(trackPad)) {

            p.fillRect(trackPad, Qt::white);

            p.setPen(QPen(QColor(224, 224, 224), 6));

            int rad = qMin(trackPad.width(), trackPad.height()) * 0.3;

            p.drawEllipse(centerPad, rad, rad);

            p.setPen(Qt::NoPen);

            p.setBrush(Qt::gray);

            QPolygon poly;

            poly << QPoint(-30, 0);

            poly << QPoint(0, -40);

            poly << QPoint(30, 0);

            p.translate(centerPad);

            for (int i = 0; i < 4; ++i) {

                p.rotate(90);

                p.translate(0, 20 - rad);

                p.drawPolygon(poly);

                p.translate(0, rad - 20);

            }

        }

        p.end();

    }

        event->accept();

        if (event->key() == Qt::Key_Left)

            angleDelta = 1.3 * M_PI;

        if (event->key() == Qt::Key_Right)

            angleDelta = -1.3 * M_PI;

        if (event->key() == Qt::Key_Up)

            moveDelta = 2.5;

        if (event->key() == Qt::Key_Down)

            moveDelta = -2.5;

    }

        event->accept();

        if (event->key() == Qt::Key_Left)

            angleDelta = (angleDelta > 0) ? 0 : angleDelta;

        if (event->key() == Qt::Key_Right)

            angleDelta = (angleDelta < 0) ? 0 : angleDelta;

        if (event->key() == Qt::Key_Up)

            moveDelta = (moveDelta > 0) ? 0 : moveDelta;

        if (event->key() == Qt::Key_Down)

            moveDelta = (moveDelta < 0) ? 0 : moveDelta;

    }

        qreal dx = centerPad.x() - event->pos().x();

        qreal dy = centerPad.y() - event->pos().y();

        angleDelta = dx * 2 * M_PI / width();

        moveDelta = dy * 10 / height();

    }

        angleDelta = 0;

        moveDelta = 0;

    }