Simple prefetch scheme

Prefetches larger set of tiles when camera is stopped

QTBUG-25136

Prefetch implementation including zoom-level prefetching
Two prefetching options- pan buffer, or pan buffer for two nearest zoom levels
Code simplified by removing all three visibleTiles lists, so they can't go out of sync
Textures not promoted up the cache if they aren't visible when retrieved from server

Also: Prefetch on map initialize + optimisation

This ensures that the prefetch is called at the end of initialisation
Useful if the location is not already in disk cache. And makes no
difference if it is already in disk cache.
QTBUG-25786

Change-Id: Ife7c1d103f83695659f4534880268fa5afd8f7c7
Reviewed-by: Alex Wilson <alex.wilson@nokia.com>

1 files changed, 15 insertions, 12 deletions

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