Optimize QGeoProjectionWebMercator::wrappedMapProjectionToItemPosition

This patch bakes all the required linear transformations performed
in the method inside a 4x4 double matrix, removing 4 of the 5
instructions previously performed.

Autotest adaptations with compares instead of verifys have been
necessary due to small epsilons in the results.

Change-Id: I7795173a27812eb93a48e3175ad24fd546aeec04
Reviewed-by: Michal Klocek <michal.klocek@qt.io>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

2 files changed, 24 insertions, 12 deletions

diff --git a/src/location/maps/qgeoprojection.cpp b/src/location/maps/qgeoprojection.cpp
index 586dcb02..8cb7a748 100644
--- a/src/location/maps/qgeoprojection.cpp
+++ b/src/location/maps/qgeoprojection.cpp
@@ -185,12 +185,7 @@ QDoubleVector2D QGeoProjectionWebMercator::unwrapMapProjection(const QDoubleVect
 
 QDoubleVector2D QGeoProjectionWebMercator::wrappedMapProjectionToItemPosition(const QDoubleVector2D &wrappedProjection) const
 {
-    QDoubleVector3D pos = wrappedProjection * m_sideLength;
-    QDoubleVector2D res =  (m_transformation * pos).toVector2D();
-    res += QDoubleVector2D(1.0,1.0);
-    res *= 0.5;
-    res *= QDoubleVector2D(m_viewportWidth, m_viewportHeight);
-    return res;
+    return (m_transformation * wrappedProjection).toVector2D();
 }
 
 QDoubleVector2D QGeoProjectionWebMercator::itemPositionToWrappedMapProjection(const QDoubleVector2D &itemPosition) const
@@ -384,7 +379,24 @@ void QGeoProjectionWebMercator::setupCamera()
     QDoubleMatrix4x4 projectionMatrix;
     projectionMatrix.frustum(-m_halfWidth, m_halfWidth, -m_halfHeight, m_halfHeight, m_nearPlane, m_farPlane);
 
-    m_transformation = projectionMatrix * cameraMatrix;
+    /*
+     * The full transformation chain for m_transformation is:
+     * matScreen * matScreenFit * matShift *  projectionMatrix * cameraMatrix * matZoomLevelScale
+     * where:
+     * matZoomLevelScale = scale(m_sideLength, m_sideLength, 1.0)
+     * matShift = translate(1.0, 1.0, 0.0)
+     * matScreenFit = scale(0.5, 0.5, 1.0)
+     * matScreen = scale(m_viewportWidth, m_viewportHeight, 1.0)
+     */
+
+    QDoubleMatrix4x4 matScreenTransformation;
+    matScreenTransformation.scale(0.5 * m_viewportWidth, 0.5 * m_viewportHeight, 1.0);
+    matScreenTransformation(0,3) = 0.5 * m_viewportWidth;
+    matScreenTransformation(1,3) = 0.5 * m_viewportHeight;
+
+    m_transformation = matScreenTransformation *  projectionMatrix * cameraMatrix;
+    m_transformation.scale(m_sideLength, m_sideLength, 1.0);
+
     m_centerNearPlane = m_eye + m_viewNormalized;
     m_centerNearPlaneMercator = m_eyeMercator + m_viewNormalized * m_nearPlaneMercator;
 
diff --git a/tests/auto/declarative_ui/tst_map_item_details.qml b/tests/auto/declarative_ui/tst_map_item_details.qml
index ebaf1ea7..0c5f5c0b 100644
--- a/tests/auto/declarative_ui/tst_map_item_details.qml
+++ b/tests/auto/declarative_ui/tst_map_item_details.qml
@@ -439,7 +439,7 @@ Item {
             // move item edge onto dateline
             extMapRectDateline.topLeft.longitude = datelineCoordinate.longitude
             point = map.fromCoordinate(extMapRectDateline.topLeft)
-            verify(point.x == map.width / 2.0)
+            compare(point.x, map.width / 2.0)
             // drag item back onto dateline
             verify(LocationTestHelper.waitForPolished(map))
             visualInspectionPoint(inspectionTime)
@@ -463,7 +463,7 @@ Item {
             verify(extMapCircleDateline.center.longitude === 180)
             map.center = datelineCoordinate
             point = map.fromCoordinate(extMapCircleDateline.center)
-            verify(point.x == map.width / 2.0) // center of the screen
+            compare(point.x, map.width / 2.0) // center of the screen
             visualInspectionPoint()
             extMapCircleDateline.center.longitude = datelineCoordinateRight.longitude // -170, moving the circle to the right
             point = map.fromCoordinate(extMapCircleDateline.center)
@@ -533,12 +533,12 @@ Item {
             path[0].longitude = datelineCoordinate.longitude;
             extMapPolygonDateline.path = path;
             point = map.fromCoordinate(extMapPolygonDateline.path[0])
-            verify(point.x == map.width / 2.0)
+            compare(point.x, map.width / 2.0)
             path = extMapPolygonDateline.path;
             path[3].longitude = datelineCoordinate.longitude;
             extMapPolygonDateline.path = path;
             point = map.fromCoordinate(extMapPolygonDateline.path[3])
-            verify(point.x == map.width / 2.0)
+            compare(point.x, map.width / 2.0)
             verify(LocationTestHelper.waitForPolished(map))
             visualInspectionPoint(inspectionTime)
             mousePress(map, point.x + 5, point.y - 5)
@@ -575,7 +575,7 @@ Item {
             path[0].longitude = datelineCoordinate.longitude;
             extMapPolylineDateline.path = path;
             point = map.fromCoordinate(extMapPolylineDateline.path[0])
-            verify(point.x == map.width / 2.0)
+            compare(point.x, map.width / 2.0)
             map.removeMapItem(extMapPolylineDateline)
 
             // map route