Unwrap longitude in Mapbox GL when needed

This is in order to keep parity with Qt visual expectations.

Change-Id: Iea758483972e53b8f42e352401390d95dd1c1407
Reviewed-by: Paolo Angelelli <paolo.angelelli@qt.io>

1 files changed, 24 insertions, 3 deletions

diff --git a/src/plugins/geoservices/mapboxgl/qmapboxglstylechange.cpp b/src/plugins/geoservices/mapboxgl/qmapboxglstylechange.cpp
index 2d3850e1..70502e70 100644
--- a/src/plugins/geoservices/mapboxgl/qmapboxglstylechange.cpp
+++ b/src/plugins/geoservices/mapboxgl/qmapboxglstylechange.cpp
@@ -62,13 +62,24 @@ QString getId(QDeclarativeGeoMapItemBase *mapItem)
     return QStringLiteral("QDeclarativeGeoMapItemBase-") + QString::number(quint64(mapItem));
 }
 
+// Mapbox GL supports geometry segments that spans above 180 degrees in
+// longitude. To keep visual expectations in parity with Qt, we need to adapt
+// the coordinates to always use the shortest path when in ambiguity.
+bool geoRectangleCrossesDateLine(const QGeoRectangle &rect) {
+    return rect.topLeft().longitude() > rect.bottomRight().longitude();
+}
+
 QMapbox::Feature featureFromMapRectangle(QDeclarativeRectangleMapItem *mapItem)
 {
     const QGeoRectangle *rect = static_cast<const QGeoRectangle *>(&mapItem->geoShape());
     QMapbox::Coordinate bottomLeft { rect->bottomLeft().latitude(), rect->bottomLeft().longitude() };
-    QMapbox::Coordinate bottomRight { rect->bottomRight().latitude(), rect->bottomRight().longitude() };
     QMapbox::Coordinate topLeft { rect->topLeft().latitude(), rect->topLeft().longitude() };
+    QMapbox::Coordinate bottomRight { rect->bottomRight().latitude(), rect->bottomRight().longitude() };
     QMapbox::Coordinate topRight { rect->topRight().latitude(), rect->topRight().longitude() };
+    if (geoRectangleCrossesDateLine(*rect)) {
+        bottomRight.second += 360.0;
+        topRight.second += 360.0;
+    }
     QMapbox::CoordinatesCollections geometry { { { bottomLeft, bottomRight, topRight, topLeft, bottomLeft } } };
 
     return QMapbox::Feature(QMapbox::Feature::PolygonType, geometry, {}, getId(mapItem));
@@ -78,8 +89,13 @@ QMapbox::Feature featureFromMapPolygon(QDeclarativePolygonMapItem *mapItem)
 {
     const QGeoPath *path = static_cast<const QGeoPath *>(&mapItem->geoShape());
     QMapbox::Coordinates coordinates;
+    const bool crossesDateline = geoRectangleCrossesDateLine(path->boundingGeoRectangle());
     for (const QGeoCoordinate &coordinate : path->path()) {
-        coordinates << QMapbox::Coordinate { coordinate.latitude(), coordinate.longitude() };
+        if (!coordinates.empty() && crossesDateline && qAbs(coordinate.longitude() - coordinates.last().second) > 180.0) {
+            coordinates << QMapbox::Coordinate { coordinate.latitude(), coordinate.longitude() + (coordinate.longitude() >= 0 ? -360.0 : 360.0) };
+        } else {
+            coordinates << QMapbox::Coordinate { coordinate.latitude(), coordinate.longitude() };
+        }
     }
     coordinates.append(coordinates.first());
     QMapbox::CoordinatesCollections geometry { { coordinates } };
@@ -91,8 +107,13 @@ QMapbox::Feature featureFromMapPolyline(QDeclarativePolylineMapItem *mapItem)
 {
     const QGeoPath *path = static_cast<const QGeoPath *>(&mapItem->geoShape());
     QMapbox::Coordinates coordinates;
+    const bool crossesDateline = geoRectangleCrossesDateLine(path->boundingGeoRectangle());
     for (const QGeoCoordinate &coordinate : path->path()) {
-        coordinates << QMapbox::Coordinate { coordinate.latitude(), coordinate.longitude() };
+        if (!coordinates.empty() && crossesDateline && qAbs(coordinate.longitude() - coordinates.last().second) > 180.0) {
+            coordinates << QMapbox::Coordinate { coordinate.latitude(), coordinate.longitude() + (coordinate.longitude() >= 0 ? -360.0 : 360.0) };
+        } else {
+            coordinates << QMapbox::Coordinate { coordinate.latitude(), coordinate.longitude() };
+        }
     }
     QMapbox::CoordinatesCollections geometry { { coordinates } };