Move the coordinate <-> item position conversion to QGeoProjection

This patch simplifies the QGeoMap API removing all the API
necessary to convert to and from screen.
This is now demanded to a specific QGeoProjection class, that will
be independent of the map, except for using the same Geo projection
(currently only WebMercator, or EPSG:3857, although we use a sphere
instead of an ellipsoid, i believe)

The benefits are
- This relieves subclasses of QGeoMap from implementing a
GeoProjection API, especially since QtLocation currently supports
only WebMercator, and reimplementations would have to anyway
produce the same results as the inbuilt one.

- This avoids the several indirection steps previously necessary
to perform a map projection (qgeotiledmap -> private->mapscene->
private). Since these operation are quite frequent one per
map item coordinate at every redraw, shortening the indirection
chain is beneficial

- It simplifies the highly complex QGeoTiledMapScene, separating
all the logic that is not needed to draw the scene, but only
to perform geo coordinate <-> screen coordinate conversion

Change-Id: I9e3ca5280166f2d6430a32deb44c030d02d9d4e1
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

1 files changed, 8 insertions, 20 deletions

diff --git a/src/location/maps/qgeomap_p.h b/src/location/maps/qgeomap_p.h
index 09da93b4..b5e51014 100644
--- a/src/location/maps/qgeomap_p.h
+++ b/src/location/maps/qgeomap_p.h
@@ -51,6 +51,7 @@
 #include <QtLocation/private/qgeomaptype_p.h>
 #include <QtCore/QObject>
 #include <QtPositioning/private/qdoublevector2d_p.h>
+#include <QtLocation/private/qgeoprojection_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -84,28 +85,15 @@ public:
     void setActiveMapType(const QGeoMapType mapType);
     const QGeoMapType activeMapType() const;
 
-    virtual double minimumZoomAtViewportSize(int viewportWidth, int viewportHeight) const = 0;
-    virtual double maximumCenterLatitudeAtZoom(double zoomLevel) const = 0;
+    // returns the minimum zoom at the current viewport size
+    double minimumZoom() const;
+    double maximumCenterLatitudeAtZoom(double zoomLevel) const;
 
-    // The size of the underlying map, at the current zoom level. Unrelated to width()/height()/size().
-    virtual double mapWidth() const = 0;
-    virtual double mapHeight() const = 0;
+    // returns the size of the underlying map, at the current zoom level. Unrelated to width()/height()/size().
+    double mapWidth() const;
+    double mapHeight() const;
 
-    // Conversion methods for QGeoCoordinate <-> screen.
-    // This currently assumes that the "MapProjection" space is [0, 1][0, 1] for every type of possibly supported map projection
-    virtual QDoubleVector2D geoToMapProjection(const QGeoCoordinate &coordinate) const = 0;
-    virtual QGeoCoordinate mapProjectionToGeo(const QDoubleVector2D &projection) const = 0;
-
-    virtual QDoubleVector2D wrapMapProjection(const QDoubleVector2D &projection) const = 0;
-    virtual QDoubleVector2D unwrapMapProjection(const QDoubleVector2D &wrappedProjection) const = 0;
-
-    virtual QDoubleVector2D wrappedMapProjectionToItemPosition(const QDoubleVector2D &wrappedProjection) const = 0;
-    virtual QDoubleVector2D itemPositionToWrappedMapProjection(const QDoubleVector2D &itemPosition) const = 0;
-
-    // Convenience methods to avoid the chain itemPositionToWrappedProjection(wrapProjection(geoToProjection()))
-    // These also come with a default implementation that can, however, be overridden.
-    virtual QGeoCoordinate itemPositionToCoordinate(const QDoubleVector2D &pos, bool clipToViewport = true) const;
-    virtual QDoubleVector2D coordinateToItemPosition(const QGeoCoordinate &coordinate, bool clipToViewport = true) const;
+    const QGeoProjection &geoProjection() const;
 
     virtual void prefetchData();
     virtual void clearData();