2 files changed, 19 insertions, 6 deletions
diff --git a/src/location/maps/qgeoprojection.cpp b/src/location/maps/qgeoprojection.cpp
index 5aaf584b..319bf906 100644
--- a/src/location/maps/qgeoprojection.cpp
+++ b/src/location/maps/qgeoprojection.cpp
@@ -93,7 +93,9 @@ QGeoProjectionWebMercator::QGeoProjectionWebMercator()
       m_farPlane(0.0),
       m_halfWidth(0.0),
       m_halfHeight(0.0),
-      m_minimumUnprojectableY(0.0)
+      m_minimumUnprojectableY(0.0),
+      m_verticalEstateToSkip(0.0),
+      m_visibleRegionDirty(false)
 {
 }
 
@@ -299,6 +301,8 @@ bool QGeoProjectionWebMercator::isProjectable(const QDoubleVector2D &wrappedProj
 
 QList<QDoubleVector2D> QGeoProjectionWebMercator::visibleRegion() const
 {
+    if (m_visibleRegionDirty)
+        const_cast<QGeoProjectionWebMercator *>(this)->updateVisibleRegion();
     return m_visibleRegion;
 }
 
@@ -444,16 +448,22 @@ void QGeoProjectionWebMercator::setupCamera()
     const double elevationUpperBound = 90.0 - upperBoundEpsilon;
     const double maxRayElevation = qMin(elevationUpperBound - m_cameraData.tilt(), verticalHalfFOV);
     double maxHalfAperture = 0;
-    double verticalEstateToSkip = 0;
+    m_verticalEstateToSkip = 0;
     if (maxRayElevation < verticalHalfFOV) {
         maxHalfAperture = tan(QLocationUtils::radians(maxRayElevation));
-        verticalEstateToSkip = 1.0 - maxHalfAperture / m_aperture;
+        m_verticalEstateToSkip = 1.0 - maxHalfAperture / m_aperture;
     }
 
-    m_minimumUnprojectableY = verticalEstateToSkip * 0.5 * m_viewportHeight; // verticalEstateToSkip is relative to half aperture
+    m_minimumUnprojectableY = m_verticalEstateToSkip * 0.5 * m_viewportHeight; // m_verticalEstateToSkip is relative to half aperture
+    m_visibleRegionDirty = true;
+}
+
+void QGeoProjectionWebMercator::updateVisibleRegion()
+{
+    m_visibleRegionDirty = false;
 
-    QDoubleVector2D tl = viewportToWrappedMapProjection(QDoubleVector2D(-1, -1 + verticalEstateToSkip ));
-    QDoubleVector2D tr = viewportToWrappedMapProjection(QDoubleVector2D( 1, -1 + verticalEstateToSkip ));
+    QDoubleVector2D tl = viewportToWrappedMapProjection(QDoubleVector2D(-1, -1 + m_verticalEstateToSkip ));
+    QDoubleVector2D tr = viewportToWrappedMapProjection(QDoubleVector2D( 1, -1 + m_verticalEstateToSkip ));
     QDoubleVector2D bl = viewportToWrappedMapProjection(QDoubleVector2D(-1,  1 ));
     QDoubleVector2D br = viewportToWrappedMapProjection(QDoubleVector2D( 1,  1 ));
 
diff --git a/src/location/maps/qgeoprojection_p.h b/src/location/maps/qgeoprojection_p.h
index b17392b1..3a0dec1d 100644
--- a/src/location/maps/qgeoprojection_p.h
+++ b/src/location/maps/qgeoprojection_p.h
@@ -131,6 +131,7 @@ public:
 
 private:
     void setupCamera();
+    void updateVisibleRegion();
 
 public:
     struct Line2D
@@ -187,6 +188,7 @@ private:
     double           m_halfWidth;
     double           m_halfHeight;
     double           m_minimumUnprojectableY;
+    double           m_verticalEstateToSkip;
 
     // For the clipping region
     QDoubleVector3D  m_centerMercator;
@@ -199,6 +201,7 @@ private:
     Line2D           m_nearPlaneMapIntersection;
 
     QList<QDoubleVector2D> m_visibleRegion;
+    bool             m_visibleRegionDirty;
 
     Q_DISABLE_COPY(QGeoProjectionWebMercator)
 };