Qt Reference Documentation

# slippymap.cpp Example File

demos/embedded/lightmaps/slippymap.cpp

     /****************************************************************************
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     ** Contact: Nokia Corporation (qt-info@nokia.com)
     **
     ** This file is part of the demonstration applications of the Qt Toolkit.
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     ** General Public License version 2.1 requirements will be met:
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     ** rights. These rights are described in the Nokia Qt LGPL Exception
     ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
     **
     ** GNU General Public License Usage
     ** Alternatively, this file may be used under the terms of the GNU General
     ** Public License version 3.0 as published by the Free Software Foundation
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     ** file. Please review the following information to ensure the GNU General
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     #include <math.h>

     #include <QtGui>
     #include <QtNetwork>
     #include "slippymap.h"

     #ifndef M_PI
     #define M_PI 3.14159265358979323846
     #endif

     uint qHash(const QPoint& p)
     {
         return p.x() * 17 ^ p.y();
     }

     // tile size in pixels
     const int tdim = 256;

     QPointF tileForCoordinate(qreal lat, qreal lng, int zoom)
     {
         qreal zn = static_cast<qreal>(1 << zoom);
         qreal tx = (lng + 180.0) / 360.0;
         qreal ty = (1.0 - log(tan(lat * M_PI / 180.0) +
                               1.0 / cos(lat * M_PI / 180.0)) / M_PI) / 2.0;
         return QPointF(tx * zn, ty * zn);
     }

     qreal longitudeFromTile(qreal tx, int zoom)
     {
         qreal zn = static_cast<qreal>(1 << zoom);
         qreal lat = tx / zn * 360.0 - 180.0;
         return lat;
     }

     qreal latitudeFromTile(qreal ty, int zoom)
     {
         qreal zn = static_cast<qreal>(1 << zoom);
         qreal n = M_PI - 2 * M_PI * ty / zn;
         qreal lng = 180.0 / M_PI * atan(0.5 * (exp(n) - exp(-n)));
         return lng;
     }

     SlippyMap::SlippyMap(QObject *parent)
         : QObject(parent), width(400), height(300), zoom(15),
           latitude(59.9138204), longitude(10.7387413)
     {
         m_emptyTile = QPixmap(tdim, tdim);
         m_emptyTile.fill(Qt::lightGray);

         QNetworkDiskCache *cache = new QNetworkDiskCache;
         cache->setCacheDirectory(QDesktopServices::storageLocation
                                     (QDesktopServices::CacheLocation));
         m_manager.setCache(cache);
         connect(&m_manager, SIGNAL(finished(QNetworkReply*)),
                 this, SLOT(handleNetworkData(QNetworkReply*)));
     }

     void SlippyMap::invalidate()
     {
         if (width <= 0 || height <= 0)
             return;

         QPointF ct = tileForCoordinate(latitude, longitude, zoom);
         qreal tx = ct.x();
         qreal ty = ct.y();

         // top-left corner of the center tile
         int xp = width / 2 - (tx - floor(tx)) * tdim;
         int yp = height / 2 - (ty - floor(ty)) * tdim;

         // first tile vertical and horizontal
         int xa = (xp + tdim - 1) / tdim;
         int ya = (yp + tdim - 1) / tdim;
         int xs = static_cast<int>(tx) - xa;
         int ys = static_cast<int>(ty) - ya;

         // offset for top-left tile
         m_offset = QPoint(xp - xa * tdim, yp - ya * tdim);

         // last tile vertical and horizontal
         int xe = static_cast<int>(tx) + (width - xp - 1) / tdim;
         int ye = static_cast<int>(ty) + (height - yp - 1) / tdim;

         // build a rect
         m_tilesRect = QRect(xs, ys, xe - xs + 1, ye - ys + 1);

         if (m_url.isEmpty())
             download();

         emit updated(QRect(0, 0, width, height));
     }

     void SlippyMap::render(QPainter *p, const QRect &rect)
     {
         for (int x = 0; x <= m_tilesRect.width(); ++x)
             for (int y = 0; y <= m_tilesRect.height(); ++y) {
                 QPoint tp(x + m_tilesRect.left(), y + m_tilesRect.top());
                 QRect box = tileRect(tp);
                 if (rect.intersects(box)) {
                     if (m_tilePixmaps.contains(tp))
                         p->drawPixmap(box, m_tilePixmaps.value(tp));
                     else
                         p->drawPixmap(box, m_emptyTile);
                 }
             }
     }

     void SlippyMap::pan(const QPoint &delta)
     {
         QPointF dx = QPointF(delta) / qreal(tdim);
         QPointF center = tileForCoordinate(latitude, longitude, zoom) - dx;
         latitude = latitudeFromTile(center.y(), zoom);
         longitude = longitudeFromTile(center.x(), zoom);
         invalidate();
     }

     void SlippyMap::handleNetworkData(QNetworkReply *reply)
     {
         QImage img;
         QPoint tp = reply->request().attribute(QNetworkRequest::User).toPoint();
         QUrl url = reply->url();
         if (!reply->error())
             if (!img.load(reply, 0))
                 img = QImage();
         reply->deleteLater();
         m_tilePixmaps[tp] = QPixmap::fromImage(img);
         if (img.isNull())
             m_tilePixmaps[tp] = m_emptyTile;
         emit updated(tileRect(tp));

         // purge unused spaces
         QRect bound = m_tilesRect.adjusted(-2, -2, 2, 2);
         foreach(QPoint tp, m_tilePixmaps.keys())
         if (!bound.contains(tp))
             m_tilePixmaps.remove(tp);

         download();
     }

     void SlippyMap::download()
     {
         QPoint grab(0, 0);
         for (int x = 0; x <= m_tilesRect.width(); ++x)
             for (int y = 0; y <= m_tilesRect.height(); ++y) {
                 QPoint tp = m_tilesRect.topLeft() + QPoint(x, y);
                 if (!m_tilePixmaps.contains(tp)) {
                     grab = tp;
                     break;
                 }
             }
         if (grab == QPoint(0, 0)) {
             m_url = QUrl();
             return;
         }

         QString path = "http://tile.openstreetmap.org/%1/%2/%3.png";
         m_url = QUrl(path.arg(zoom).arg(grab.x()).arg(grab.y()));
         QNetworkRequest request;
         request.setUrl(m_url);
         request.setRawHeader("User-Agent", "Nokia (Qt) Graphics Dojo 1.0");
         request.setAttribute(QNetworkRequest::User, QVariant(grab));
         m_manager.get(request);
     }

     QRect SlippyMap::tileRect(const QPoint &tp)
     {
         QPoint t = tp - m_tilesRect.topLeft();
         int x = t.x() * tdim + m_offset.x();
         int y = t.y() * tdim + m_offset.y();
         return QRect(x, y, tdim, tdim);
     }