14 files changed, 155 insertions, 45 deletions

diff --git a/src/location/maps/qgeocameratiles.cpp b/src/location/maps/qgeocameratiles.cpp
index 9258661b..a63420ed 100644
--- a/src/location/maps/qgeocameratiles.cpp
+++ b/src/location/maps/qgeocameratiles.cpp
@@ -58,6 +58,11 @@
 #include <cmath>
 
 QT_BEGIN_NAMESPACE
+#define ENABLE_PREFETCHING
+// larger values fetch a bigger set when the camera stops
+#define PREFETCH_FRUSTUM_SCALE 2.0
+// #define PREFETCH_NEIGHBOUR_LAYER
+#define PREFETCH_TWO_NEIGHBOUR_LAYERS
 
 struct Frustum
 {
@@ -91,9 +96,9 @@ public:
     int sideLength_;
 
     void updateMetadata();
-    void updateGeometry();
+    void updateGeometry(double viewExpansion = 1.0);
 
-    Frustum frustum() const;
+    Frustum frustum(double fieldOfViewGradient) const;
 
     class LengthSorter
     {
@@ -132,18 +137,78 @@ QGeoCameraTiles::~QGeoCameraTiles()
     delete d_ptr;
 }
 
+void QGeoCameraTiles::findPrefetchTiles()
+{
+#if defined(ENABLE_PREFETCHING)
+    Q_D(QGeoCameraTiles);
+
+    d->tiles_.clear();
+
+    // qDebug() << "prefetch called";
+    int zoom = static_cast<int>(floor(d->camera_.zoomLevel()));
+    d->intZoomLevel_ = zoom;
+    d->sideLength_ = 1 << d->intZoomLevel_;
+    d->updateGeometry(PREFETCH_FRUSTUM_SCALE);
+
+#if defined(PREFETCH_NEIGHBOUR_LAYER)
+    double zoomFraction = d->camera_.zoomLevel() - zoom;
+    int nearestNeighbourLayer = zoomFraction > 0.5 ? zoom + 1 : zoom - 1;
+    if (nearestNeighbourLayer <= d->maxZoom_ && nearestNeighbourLayer >= 0)
+    {
+        double oldZoom = d->camera_.zoomLevel();
+        d->intZoomLevel_ = nearestNeighbourLayer;
+        d->sideLength_ = 1 << d->intZoomLevel_;
+        d->camera_.setZoomLevel(d->intZoomLevel_);
+
+        // Approx heuristic, keeping total # prefetched tiles roughly independent of the
+        // fractional zoom level.
+        double neighbourScale = (1.0 + zoomFraction)/2.0;
+
+        d->updateGeometry(PREFETCH_FRUSTUM_SCALE * neighbourScale);
+        d->camera_.setZoomLevel(oldZoom);
+    }
+#elif defined(PREFETCH_TWO_NEIGHBOUR_LAYERS)
+ //   int size1 = d->tiles_.size();
+
+    // This is a simpler strategy, we just prefetch from layer above and below
+    // for the layer below we only use half the size as this fills the screen
+    double oldZoom = d->camera_.zoomLevel();
+    if (zoom > 0)
+    {
+        d->intZoomLevel_ = zoom-1;
+        d->sideLength_ = 1 << d->intZoomLevel_;
+        d->camera_.setZoomLevel(d->intZoomLevel_);
+        d->updateGeometry(0.5);
+    }
+ //   int size2 = d->tiles_.size();
+    if (zoom < d->maxZoom_)
+    {
+        d->intZoomLevel_ = zoom+1;
+        d->sideLength_ = 1 << d->intZoomLevel_;
+        d->camera_.setZoomLevel(d->intZoomLevel_);
+        d->updateGeometry(1.0);
+    }
+ //   qDebug() << "prefetched main tiles: " << size1 << " higher detail layer: " << d->tiles_.size() - size2 << " low detail layer: " << size2 - size1;
+    d->intZoomLevel_ = zoom;
+    d->sideLength_ = 1 << d->intZoomLevel_;
+    d->camera_.setZoomLevel(oldZoom);
+#endif
+#endif
+}
+
+
 void QGeoCameraTiles::setCamera(const QGeoCameraData &camera)
 {
     Q_D(QGeoCameraTiles);
 
     if (d->camera_ == camera)
         return;
-
     d->camera_ = camera;
 
     d->intZoomLevel_ = static_cast<int>(floor(d->camera_.zoomLevel()));
     d->sideLength_ = 1 << d->intZoomLevel_;
 
+    d->tiles_.clear();
     d->updateGeometry();
 }
 
@@ -155,6 +220,7 @@ void QGeoCameraTiles::setScreenSize(const QSize &size)
         return;
 
     d->screenSize_ = size;
+    d->tiles_.clear();
     d->updateGeometry();
 }
 
@@ -188,6 +254,7 @@ void QGeoCameraTiles::setTileSize(int tileSize)
         return;
 
     d->tileSize_ = tileSize;
+    d->tiles_.clear();
     d->updateGeometry();
 }
 
@@ -205,6 +272,7 @@ void QGeoCameraTiles::setMaximumZoomLevel(int maxZoom)
         return;
 
     d->maxZoom_ = maxZoom;
+    d->tiles_.clear();
     d->updateGeometry();
 }
 
@@ -239,12 +307,11 @@ void QGeoCameraTilesPrivate::updateMetadata()
     tiles_ = newTiles;
 }
 
-void QGeoCameraTilesPrivate::updateGeometry()
+void QGeoCameraTilesPrivate::updateGeometry(double viewExpansion)
 {
-    tiles_.clear();
-
     // Find the frustum from the camera / screen / viewport information
-    Frustum f = frustum();
+    // The larger frustum when stationary is a form of prefetching
+    Frustum f = frustum(viewExpansion);
 
     // Find the polygon where the frustum intersects the plane of the map
     Polygon footprint = frustumFootprint(f);
@@ -263,7 +330,7 @@ void QGeoCameraTilesPrivate::updateGeometry()
     }
 }
 
-Frustum QGeoCameraTilesPrivate::frustum() const
+Frustum QGeoCameraTilesPrivate::frustum(double fieldOfViewGradient) const
 {
     QDoubleVector3D center = sideLength_ * QGeoProjection::coordToMercator(camera_.center());
     center.setZ(0.0);
@@ -294,16 +361,16 @@ Frustum QGeoCameraTilesPrivate::frustum() const
     // this assumes that viewSize = 2*nearPlane x 2*nearPlane
 
     if (aspectRatio > 1.0) {
-        hn = 2 * nearPlane;
+        hn = 2 * fieldOfViewGradient * nearPlane;
         wn = hn * aspectRatio;
 
-        hf = 2 * farPlane;
+        hf = 2 * fieldOfViewGradient * farPlane;
         wf = hf * aspectRatio;
     } else {
-        wn = 2 * nearPlane;
+        wn = 2 * fieldOfViewGradient * nearPlane;
         hn = wn / aspectRatio;
 
-        wf = 2 * farPlane;
+        wf = 2 * fieldOfViewGradient * farPlane;
         hf = wf / aspectRatio;
     }
 
diff --git a/src/location/maps/qgeocameratiles_p.h b/src/location/maps/qgeocameratiles_p.h
index dfc8cdf3..30571f72 100644
--- a/src/location/maps/qgeocameratiles_p.h
+++ b/src/location/maps/qgeocameratiles_p.h
@@ -82,6 +82,7 @@ public:
     void setMapType(const QGeoMapType &mapType);
 
     QSet<QGeoTileSpec> tiles() const;
+    void findPrefetchTiles();
 
 private:
     QGeoCameraTilesPrivate *d_ptr;
diff --git a/src/location/maps/qgeomap.cpp b/src/location/maps/qgeomap.cpp
index 7001c7c7..ad81fd13 100644
--- a/src/location/maps/qgeomap.cpp
+++ b/src/location/maps/qgeomap.cpp
@@ -129,6 +129,11 @@ void QGeoMap::setCameraData(const QGeoCameraData &cameraData)
     mapData_->setCameraData(cameraData);
 }
 
+void QGeoMap::cameraStopped()
+{
+    mapData_->prefetchData();
+}
+
 QGeoCameraData QGeoMap::cameraData() const
 {
     return mapData_->cameraData();
diff --git a/src/location/maps/qgeomap_p.h b/src/location/maps/qgeomap_p.h
index 34771fe4..a16ad7d6 100644
--- a/src/location/maps/qgeomap_p.h
+++ b/src/location/maps/qgeomap_p.h
@@ -108,6 +108,7 @@ public:
 
 public Q_SLOTS:
     void update();
+    void cameraStopped(); // optional hint for prefetch
 
 Q_SIGNALS:
     void cameraDataChanged(const QGeoCameraData &cameraData);
diff --git a/src/location/maps/qgeomapdata.cpp b/src/location/maps/qgeomapdata.cpp
index 955b426b..1f0d5cc6 100644
--- a/src/location/maps/qgeomapdata.cpp
+++ b/src/location/maps/qgeomapdata.cpp
@@ -119,7 +119,6 @@ int QGeoMapData::height() const
 void QGeoMapData::setCameraData(const QGeoCameraData &cameraData)
 {
     Q_D(QGeoMapData);
-
     if (cameraData == d->cameraData())
         return;
 
@@ -270,7 +269,13 @@ void QGeoMapDataPrivate::setCameraData(const QGeoCameraData &cameraData)
     }
 
     cameraData_.setCoordinateInterpolator(coordinateInterpolator_.toWeakRef());
-    map_->changeCameraData(oldCameraData);
+
+    // Do not call this expensive function if the width is 0, since it will get called
+    // anyway when it is resized to a width > 0.
+    // this is mainly an optimisation to the initalization of the geomap, which would otherwise
+    // call changeCameraData four or more times
+    if (width() > 0)
+        map_->changeCameraData(oldCameraData);
 }
 
 QGeoCameraData QGeoMapDataPrivate::cameraData() const
diff --git a/src/location/maps/qgeomapdata_p.h b/src/location/maps/qgeomapdata_p.h
index 42367ced..f1304ff9 100644
--- a/src/location/maps/qgeomapdata_p.h
+++ b/src/location/maps/qgeomapdata_p.h
@@ -106,6 +106,7 @@ public:
     QString pluginString();
     QGeoCameraCapabilities cameraCapabilities();
     QGeoMappingManagerEngine *engine();
+    virtual void prefetchData() = 0;
 
 protected:
     void setCoordinateInterpolator(QSharedPointer<QGeoCoordinateInterpolator> interpolator);
diff --git a/src/location/maps/qgeomapscene.cpp b/src/location/maps/qgeomapscene.cpp
index c8b39232..7aea014d 100644
--- a/src/location/maps/qgeomapscene.cpp
+++ b/src/location/maps/qgeomapscene.cpp
@@ -231,6 +231,16 @@ void QGeoMapScene::paintGL(QGLPainter *painter)
     d->paintGL(painter);
 }
 
+QSet<QGeoTileSpec> QGeoMapScene::texturedTiles()
+{
+    Q_D(QGeoMapScene);
+    QSet<QGeoTileSpec> textured;
+    foreach (const QGeoTileSpec &tile, d->textures_.keys()) {
+        textured += tile;
+    }
+    return textured;
+}
+
 QGeoMapScenePrivate::QGeoMapScenePrivate(QGeoMapScene *scene)
     : tileSize_(0),
       camera_(new QGLCamera()),
@@ -400,6 +410,8 @@ void QGeoMapScenePrivate::setScalingOnTextures()
 
 void QGeoMapScenePrivate::addTile(const QGeoTileSpec &spec, QSharedPointer<QGeoTileTexture> texture)
 {
+    if (!visibleTiles_.contains(spec)) // Don't add the geometry if it isn't visible
+        return;
     if (linearScaling_) {
         texture->texture->setBindOptions(texture->texture->bindOptions() |
                                          (QGLTexture2D::LinearFilteringBindOption));
diff --git a/src/location/maps/qgeomapscene_p.h b/src/location/maps/qgeomapscene_p.h
index 9ff7969d..d2baa99e 100644
--- a/src/location/maps/qgeomapscene_p.h
+++ b/src/location/maps/qgeomapscene_p.h
@@ -101,6 +101,7 @@ public:
     void paintGL(QGLPainter *painter);
 
     bool verticalLock() const;
+    QSet<QGeoTileSpec> texturedTiles();
 
 Q_SIGNALS:
     void newTilesVisible(const QSet<QGeoTileSpec> &newTiles);
diff --git a/src/location/maps/qgeotiledmapdata.cpp b/src/location/maps/qgeotiledmapdata.cpp
index 0d331625..c1a6bdff 100644
--- a/src/location/maps/qgeotiledmapdata.cpp
+++ b/src/location/maps/qgeotiledmapdata.cpp
@@ -149,10 +149,10 @@ QGeoTileRequestManager *QGeoTiledMapData::getRequestManager()
     return d->tileRequests_;
 }
 
-void QGeoTiledMapData::newTileFetched(QSharedPointer<QGeoTileTexture> texture)
+void QGeoTiledMapData::newTileFetched(const QGeoTileSpec &spec)
 {
     Q_D(QGeoTiledMapData);
-    d->newTileFetched(texture);
+    d->newTileFetched(spec);
 }
 
 QGeoTileCache *QGeoTiledMapData::tileCache()
@@ -180,6 +180,12 @@ void QGeoTiledMapData::changeCameraData(const QGeoCameraData &oldCameraData)
     d->changeCameraData(oldCameraData);
 }
 
+void QGeoTiledMapData::prefetchData()
+{
+    Q_D(QGeoTiledMapData);
+    d->prefetchTiles();
+}
+
 void QGeoTiledMapData::changeActiveMapType(const QGeoMapType mapType)
 {
     Q_D(QGeoTiledMapData);
@@ -263,6 +269,14 @@ QGeoTiledMappingManagerEngine *QGeoTiledMapDataPrivate::engine() const
     return engine_;
 }
 
+void QGeoTiledMapDataPrivate::prefetchTiles()
+{
+    cameraTiles_->findPrefetchTiles();
+
+    if (tileRequests_)
+        tileRequests_->requestTiles(cameraTiles_->tiles() - mapScene_->texturedTiles());
+}
+
 void QGeoTiledMapDataPrivate::changeCameraData(const QGeoCameraData &oldCameraData)
 {
     double lat = oldCameraData.center().latitude();
@@ -288,14 +302,14 @@ void QGeoTiledMapDataPrivate::changeCameraData(const QGeoCameraData &oldCameraDa
     }
 
     cameraTiles_->setCamera(cam);
-    visibleTiles_ = cameraTiles_->tiles();
 
     mapScene_->setCameraData(cam);
-    mapScene_->setVisibleTiles(visibleTiles_);
+    mapScene_->setVisibleTiles(cameraTiles_->tiles());
 
     if (tileRequests_) {
+        // don't request tiles that are already built and textured
         QList<QSharedPointer<QGeoTileTexture> > cachedTiles =
-                tileRequests_->requestTiles(visibleTiles_);
+                tileRequests_->requestTiles(cameraTiles_->tiles() - mapScene_->texturedTiles());
 
         foreach (const QSharedPointer<QGeoTileTexture> &tex, cachedTiles) {
             mapScene_->addTile(tex->spec, tex);
@@ -303,14 +317,12 @@ void QGeoTiledMapDataPrivate::changeCameraData(const QGeoCameraData &oldCameraDa
 
         if (!cachedTiles.isEmpty())
             map_->update();
-
     }
 }
 
 void QGeoTiledMapDataPrivate::changeActiveMapType(const QGeoMapType mapType)
 {
     cameraTiles_->setMapType(mapType);
-    visibleTiles_ = cameraTiles_->tiles();
 }
 
 void QGeoTiledMapDataPrivate::resized(int width, int height)
@@ -337,15 +349,18 @@ void QGeoTiledMapDataPrivate::resized(int width, int height)
     }
 }
 
-void QGeoTiledMapDataPrivate::newTileFetched(QSharedPointer<QGeoTileTexture> texture)
+void QGeoTiledMapDataPrivate::newTileFetched(const QGeoTileSpec &spec)
 {
-    mapScene_->addTile(texture->spec, texture);
-    map_->update();
+    // Only promote the texture up to GPU if it is visible
+    if (cameraTiles_->tiles().contains(spec)){
+        mapScene_->addTile(spec, engine_->getTileTexture(spec));
+        map_->update();
+    }
 }
 
 QSet<QGeoTileSpec> QGeoTiledMapDataPrivate::visibleTiles()
 {
-    return visibleTiles_;
+    return cameraTiles_->tiles();
 }
 
 void QGeoTiledMapDataPrivate::paintGL(QGLPainter *painter)
diff --git a/src/location/maps/qgeotiledmapdata_p.h b/src/location/maps/qgeotiledmapdata_p.h
index 73fde8f1..db160fe9 100644
--- a/src/location/maps/qgeotiledmapdata_p.h
+++ b/src/location/maps/qgeotiledmapdata_p.h
@@ -82,10 +82,11 @@ public:
 
     void paintGL(QGLPainter *painter);
 
-    void newTileFetched(QSharedPointer<QGeoTileTexture> texture);
+    void newTileFetched(const QGeoTileSpec &spec);
 
     QGeoCoordinate screenPositionToCoordinate(const QPointF &pos, bool clipToViewport = true) const;
     QPointF coordinateToScreenPosition(const QGeoCoordinate &coordinate, bool clipToViewport = true) const;
+    void prefetchTiles();
 
     // Alternative to exposing this is to make tileFetched a slot, but then requestManager would
     // need to be a QObject
@@ -94,6 +95,7 @@ protected:
     void mapResized(int width, int height);
     void changeCameraData(const QGeoCameraData &oldCameraData);
     void changeActiveMapType(const QGeoMapType mapType);
+    void prefetchData();
 
 protected Q_SLOTS:
     virtual void evaluateCopyrights(const QSet<QGeoTileSpec> &visibleTiles);
diff --git a/src/location/maps/qgeotiledmapdata_p_p.h b/src/location/maps/qgeotiledmapdata_p_p.h
index e1d2d716..79af86fb 100644
--- a/src/location/maps/qgeotiledmapdata_p_p.h
+++ b/src/location/maps/qgeotiledmapdata_p_p.h
@@ -101,18 +101,17 @@ public:
     QGeoCoordinate screenPositionToCoordinate(const QPointF &pos) const;
     QPointF coordinateToScreenPosition(const QGeoCoordinate &coordinate) const;
 
-    void newTileFetched(QSharedPointer<QGeoTileTexture> texture);
+    void newTileFetched(const QGeoTileSpec &spec);
     QSet<QGeoTileSpec> visibleTiles();
 
     QGeoTiledMappingManagerEngine *engine() const;
+    void prefetchTiles();
 
 private:
     QGeoTiledMapData *map_;
     QGeoTileCache *cache_;
     QGeoTiledMappingManagerEngine *engine_;
 
-    QSet<QGeoTileSpec> visibleTiles_;
-
     QGeoCameraTiles *cameraTiles_;
     QGeoMapScene *mapScene_;
     Q_DISABLE_COPY(QGeoTiledMapDataPrivate)
diff --git a/src/location/maps/qgeotiledmappingmanagerengine.cpp b/src/location/maps/qgeotiledmappingmanagerengine.cpp
index 0a7b11b7..3dafc302 100644
--- a/src/location/maps/qgeotiledmappingmanagerengine.cpp
+++ b/src/location/maps/qgeotiledmappingmanagerengine.cpp
@@ -239,12 +239,10 @@ void QGeoTiledMappingManagerEngine::engineTileFinished(const QGeoTileSpec &spec,
 
     tileCache()->insert(spec, bytes, format, d->cacheHint_);
 
-    QSharedPointer<QGeoTileTexture> tile = tileCache()->get(spec);
-
     map = maps.constBegin();
     mapEnd = maps.constEnd();
     for (; map != mapEnd; ++map) {
-        (*map)->getRequestManager()->tileFetched(tile);
+        (*map)->getRequestManager()->tileFetched(spec);
     }
 }
 
diff --git a/src/location/maps/qgeotilerequestmanager.cpp b/src/location/maps/qgeotilerequestmanager.cpp
index 563df456..431a3c26 100644
--- a/src/location/maps/qgeotilerequestmanager.cpp
+++ b/src/location/maps/qgeotilerequestmanager.cpp
@@ -41,6 +41,7 @@
 #include "qgeotilerequestmanager_p.h"
 
 #include <QSharedPointer>
+#include <QDebug>
 #include "qgeotilespec.h"
 #include "qgeotiledmapdata_p.h"
 #include "qgeotiledmappingmanagerengine.h"
@@ -64,10 +65,9 @@ public:
 
     QHash<QGeoTileSpec, int> retries_;
     QHash<QGeoTileSpec, QSharedPointer<RetryFuture> > futures_;
-    QSet<QGeoTileSpec> visible_;
     QSet<QGeoTileSpec> requested_;
 
-    void tileFetched(QSharedPointer<QGeoTileTexture> texture);
+    void tileFetched(const QGeoTileSpec &spec);
 };
 
 QGeoTileRequestManager::QGeoTileRequestManager(QGeoTiledMapData *map)
@@ -86,10 +86,10 @@ QList<QSharedPointer<QGeoTileTexture> > QGeoTileRequestManager::requestTiles(con
     return d->requestTiles(tiles);
 }
 
-void QGeoTileRequestManager::tileFetched(QSharedPointer<QGeoTileTexture> texture)
+void QGeoTileRequestManager::tileFetched(const QGeoTileSpec &spec)
 {
     Q_D(QGeoTileRequestManager);
-    d->tileFetched(texture);
+    d->tileFetched(spec);
 }
 
 void QGeoTileRequestManager::tileError(const QGeoTileSpec &tile, const QString &errorString)
@@ -110,8 +110,10 @@ QGeoTileRequestManagerPrivate::~QGeoTileRequestManagerPrivate()
 QList<QSharedPointer<QGeoTileTexture> > QGeoTileRequestManagerPrivate::requestTiles(const QSet<QGeoTileSpec> &tiles)
 {
     QSet<QGeoTileSpec> cancelTiles = requested_ - tiles;
-    QSet<QGeoTileSpec> requestTiles = tiles - visible_ - requested_;
+    QSet<QGeoTileSpec> requestTiles = tiles - requested_;
     QSet<QGeoTileSpec> cached;
+//    int tileSize = tiles.size();
+//    int newTiles = requestTiles.size();
 
     typedef QSet<QGeoTileSpec>::const_iterator iter;
 
@@ -136,13 +138,14 @@ QList<QSharedPointer<QGeoTileTexture> > QGeoTileRequestManagerPrivate::requestTi
 
     requestTiles -= cached;
 
-    visible_ = tiles;
-
     requested_ -= cancelTiles;
     requested_ += requestTiles;
 
+//    qDebug() << "required # tiles: " << tileSize << ", new tiles: " << newTiles << ", total server requests: " << requested_.size();
+
     if (!requestTiles.isEmpty() || !cancelTiles.isEmpty()) {
         if (engine) {
+//            qDebug() << "new server requests: " << requestTiles.size() << ", server cancels: " << cancelTiles.size();
             engine->updateTileRequests(map_, requestTiles, cancelTiles);
 
             // Remove any cancelled tiles from the error retry hash to avoid
@@ -159,12 +162,12 @@ QList<QSharedPointer<QGeoTileTexture> > QGeoTileRequestManagerPrivate::requestTi
     return cachedTex;
 }
 
-void QGeoTileRequestManagerPrivate::tileFetched(QSharedPointer<QGeoTileTexture> texture)
+void QGeoTileRequestManagerPrivate::tileFetched(const QGeoTileSpec &spec)
 {
-    map_->newTileFetched(texture);
-    requested_.remove(texture->spec);
-    retries_.remove(texture->spec);
-    futures_.remove(texture->spec);
+    map_->newTileFetched(spec);
+    requested_.remove(spec);
+    retries_.remove(spec);
+    futures_.remove(spec);
 }
 
 // Represents a tile that needs to be retried after a certain period of time
diff --git a/src/location/maps/qgeotilerequestmanager_p.h b/src/location/maps/qgeotilerequestmanager_p.h
index 3f394de8..47d1b08a 100644
--- a/src/location/maps/qgeotilerequestmanager_p.h
+++ b/src/location/maps/qgeotilerequestmanager_p.h
@@ -76,7 +76,7 @@ public:
     QList<QSharedPointer<QGeoTileTexture> > requestTiles(const QSet<QGeoTileSpec> &tiles);
 
     void tileError(const QGeoTileSpec &tile, const QString &errorString);
-    void tileFetched(QSharedPointer<QGeoTileTexture> texture);
+    void tileFetched(const QGeoTileSpec &spec);
 private:
     QGeoTileRequestManagerPrivate *d_ptr;
     Q_DECLARE_PRIVATE(QGeoTileRequestManager)