Add support for unitary tile cost in QGeoFileTileCache

This patch adds support for unitary pricing of tiles in the disk, memory
and texture caches.
This is done through a new enum in QAbstractGeoTileCache, "CostStrategy"
having two values, Unitary (new one) and ByteSize (the old way).

Using Unitary instead of ByteSize gives, as advantages:
- the ability to comply with the TOS of certain providers, who allow to
cache a fixed number of tiles, and not of bytes.
- even performance with different types of tiles, like lo vs hi res,
indexed vs satellite (which usually compresses much less).

This patch sets the Unitary mode to be the default for the mapbox plugin
since Mapbox is one of the providers whose TOS limit the amount of
cacheable tiles.
Therefore, the patch also modifies the mapbox plugin ".mapping.cache"
parameters to reflect the new behavior.
Since these parameters have been introduced with 5.8 (which is
unreleased), the change doesn't need to be backward compatible.

Change-Id: I76edd43900242885f24eb9f28e8c833538647edc
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/location/maps/qgeofiletilecache_p.h b/src/location/maps/qgeofiletilecache_p.h
index e850a13b..96fcf1ee 100644
--- a/src/location/maps/qgeofiletilecache_p.h
+++ b/src/location/maps/qgeofiletilecache_p.h
@@ -118,6 +118,9 @@ public:
     int textureUsage() const Q_DECL_OVERRIDE;
     void clearAll() Q_DECL_OVERRIDE;
     void clearMapId(const int mapId);
+    void setCostStrategy(CostStrategy costStrategy) Q_DECL_OVERRIDE;
+    CostStrategy costStrategy() Q_DECL_OVERRIDE;
+
 
     QSharedPointer<QGeoTileTexture> get(const QGeoTileSpec &spec) Q_DECL_OVERRIDE;
 
@@ -154,6 +157,7 @@ protected:
 
     int minTextureUsage_;
     int extraTextureUsage_;
+    CostStrategy costStrategy_;
 };
 
 QT_END_NAMESPACE