Allow plugins to use alternative map projections

QtLocation mapping has always been geared around the WebMercator
projection. Some mapping SDKs support additional projections, such
as General Perspective (often called globe view or globe rendering).

The goal of this patch is to allow a plugin to provide such a view,
disabling WebMercator specific features, and redirecting API calls
to plugin-specific implementations.

In particular, this patch disables the rendering of Map Items
(QDeclarativeGeoMapItemBase and sons) for projections different from
WebMercator, with the exception of MapQuickItems.
MapQuickItems, in turn, lose the ability to draw "on the map", when
the projection is different from WebMercator. However, they can still
be used to add geolocated popups, buttons and other UI elements.

fitViewportToMapItems is also disabled, for both it can't be computed
and there wouldn't be any item to fit (with the exception of
mapquickitems)

Change-Id: I9fa2fdd01a35a078fc4663efc9d269c4ecaa3f41
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

1 files changed, 16 insertions, 12 deletions

diff --git a/src/location/declarativemaps/qdeclarativepolylinemapitem.cpp b/src/location/declarativemaps/qdeclarativepolylinemapitem.cpp
index 7c1b922f..90ed95e4 100644
--- a/src/location/declarativemaps/qdeclarativepolylinemapitem.cpp
+++ b/src/location/declarativemaps/qdeclarativepolylinemapitem.cpp
@@ -189,11 +189,11 @@ QList<QList<QDoubleVector2D> > QGeoMapPolylineGeometry::clipPath(const QGeoMap &
      * 2.1) recalculate the origin and geoLeftBound to prevent these parameters from ending in unprojectable areas
      * 2.2) ensure the left bound does not wrap around due to QGeoCoordinate <-> clipper conversions
      */
-
+    const QGeoProjectionWebMercator &p = static_cast<const QGeoProjectionWebMercator&>(map.geoProjection());
     srcOrigin_ = geoLeftBound_;
 
     double unwrapBelowX = 0;
-    leftBoundWrapped = map.geoProjection().wrapMapProjection(map.geoProjection().geoToMapProjection(geoLeftBound_));
+    leftBoundWrapped = p.wrapMapProjection(p.geoToMapProjection(geoLeftBound_));
     if (preserveGeometry_)
         unwrapBelowX = leftBoundWrapped.x();
 
@@ -203,7 +203,7 @@ QList<QList<QDoubleVector2D> > QGeoMapPolylineGeometry::clipPath(const QGeoMap &
     // 1)
     for (int i = 0; i < path.size(); ++i) {
         const QDoubleVector2D &coord = path.at(i);
-        QDoubleVector2D wrappedProjection = map.geoProjection().wrapMapProjection(coord);
+        QDoubleVector2D wrappedProjection = p.wrapMapProjection(coord);
 
         // We can get NaN if the map isn't set up correctly, or the projection
         // is faulty -- probably best thing to do is abort
@@ -226,7 +226,7 @@ QList<QList<QDoubleVector2D> > QGeoMapPolylineGeometry::clipPath(const QGeoMap &
 
     // 2)
     QList<QList<QDoubleVector2D> > clippedPaths;
-    const QList<QDoubleVector2D> &visibleRegion = map.geoProjection().projectableRegion();
+    const QList<QDoubleVector2D> &visibleRegion = p.projectableGeometry();
     if (visibleRegion.size()) {
         c2t::clip2tri clipper;
         clipper.addSubjectPath(QClipperUtils::qListToPath(wrappedPath), false);
@@ -265,18 +265,19 @@ void QGeoMapPolylineGeometry::pathToScreen(const QGeoMap &map,
                                            const QList<QList<QDoubleVector2D> > &clippedPaths,
                                            const QDoubleVector2D &leftBoundWrapped)
 {
+    const QGeoProjectionWebMercator &p = static_cast<const QGeoProjectionWebMercator&>(map.geoProjection());
     // 3) project the resulting geometry to screen position and calculate screen bounds
     double minX = qInf();
     double minY = qInf();
     double maxX = -qInf();
     double maxY = -qInf();
 
-    srcOrigin_ = map.geoProjection().mapProjectionToGeo(map.geoProjection().unwrapMapProjection(leftBoundWrapped));
-    QDoubleVector2D origin = map.geoProjection().wrappedMapProjectionToItemPosition(leftBoundWrapped);
+    srcOrigin_ = p.mapProjectionToGeo(p.unwrapMapProjection(leftBoundWrapped));
+    QDoubleVector2D origin = p.wrappedMapProjectionToItemPosition(leftBoundWrapped);
     for (const QList<QDoubleVector2D> &path: clippedPaths) {
         QDoubleVector2D lastAddedPoint;
         for (int i = 0; i < path.size(); ++i) {
-            QDoubleVector2D point = map.geoProjection().wrappedMapProjectionToItemPosition(path.at(i));
+            QDoubleVector2D point = p.wrappedMapProjectionToItemPosition(path.at(i));
 
             point = point - origin; // (0,0) if point == geoLeftBound_
 
@@ -722,12 +723,13 @@ void QDeclarativePolylineMapItem::afterViewportChanged(const QGeoMapViewportChan
 */
 void QDeclarativePolylineMapItem::regenerateCache()
 {
-    if (!map())
+    if (!map() || map()->geoProjection().projectionType() != QGeoProjection::ProjectionWebMercator)
         return;
+    const QGeoProjectionWebMercator &p = static_cast<const QGeoProjectionWebMercator&>(map()->geoProjection());
     geopathProjected_.clear();
     geopathProjected_.reserve(geopath_.path().size());
     for (const QGeoCoordinate &c : geopath_.path())
-        geopathProjected_ << map()->geoProjection().geoToMapProjection(c);
+        geopathProjected_ << p.geoToMapProjection(c);
 }
 
 /*!
@@ -735,9 +737,10 @@ void QDeclarativePolylineMapItem::regenerateCache()
 */
 void QDeclarativePolylineMapItem::updateCache()
 {
-    if (!map())
+    if (!map() ||  map()->geoProjection().projectionType() != QGeoProjection::ProjectionWebMercator)
         return;
-    geopathProjected_ << map()->geoProjection().geoToMapProjection(geopath_.path().last());
+    const QGeoProjectionWebMercator &p = static_cast<const QGeoProjectionWebMercator&>(map()->geoProjection());
+    geopathProjected_ << p.geoToMapProjection(geopath_.path().last());
 }
 
 /*!
@@ -745,7 +748,8 @@ void QDeclarativePolylineMapItem::updateCache()
 */
 void QDeclarativePolylineMapItem::updatePolish()
 {
-    if (!map() || geopath_.path().length() == 0)
+    if (!map() || geopath_.path().length() == 0
+            || map()->geoProjection().projectionType() != QGeoProjection::ProjectionWebMercator)
         return;
 
     QScopedValueRollback<bool> rollback(updatingGeometry_);