Fix visible region computation in QGeoProjectionWebMercator

Currently the visible region is calculated as the intersection between
the viewing frustum and the map plane clipped against the map extended
rectangle in mercator space (from -1 to 2 in x coords, 0 to 1 in y
coords).

The result is correct in the extended mercator space. However, this may
lead to overlapping coordinates when converted back to latitude and
longitude.

For this reason, this patch changes the clipping geometry to be the
map un-extended rectangle centered around the current map center.
The result is a geometry that never wraps around or overlaps, thus
removing the need for handling separately the case when the map
is fully visible when returning the visible region.

Task-number: QTBUG-57690
Change-Id: I8396c40a123ce94bff4388dfefbd8a694657b8bd
Reviewed-by: BogDan Vatra <bogdan@kdab.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/tests/auto/declarative_ui/tst_map.qml b/tests/auto/declarative_ui/tst_map.qml
index 846a621f..408bf96e 100644
--- a/tests/auto/declarative_ui/tst_map.qml
+++ b/tests/auto/declarative_ui/tst_map.qml
@@ -30,6 +30,7 @@ import QtQuick 2.0
 import QtTest 1.0
 import QtPositioning 5.5
 import QtLocation 5.9
+import QtLocation.Test 5.6
 
 Item {
     width:100
@@ -55,6 +56,10 @@ Item {
     property variant coordinate3: QtPositioning.coordinate(50, 50, 0)
     property variant coordinate4: QtPositioning.coordinate(80, 80, 0)
     property variant coordinate5: QtPositioning.coordinate(20, 180)
+    property variant coordinateCenterVisibleRegion: QtPositioning.coordinate(27, 77)
+    property variant coordinateVisible1: QtPositioning.coordinate(28, 77)
+    property variant coordinateVisible2: QtPositioning.coordinate(33, 79.1)
+    property variant coordinateVisible3: QtPositioning.coordinate(27, 80.5)
     property variant invalidCoordinate: QtPositioning.coordinate()
     property variant altitudelessCoordinate: QtPositioning.coordinate(50, 50)
     property bool allMapsReady: mapZoomOnCompleted.mapReady
@@ -84,6 +89,9 @@ Item {
         }
     }
 
+    Map { id: mapVisibleRegion; width: 800; height: 600;
+        center: coordinateCenterVisibleRegion; plugin: testPlugin; zoomLevel: 1.0 }
+
     Map {id: map; plugin: testPlugin; center: coordinate1; width: 100; height: 100}
     SignalSpy {id: mapCenterSpy; target: map; signalName: 'centerChanged'}
 
@@ -148,6 +156,39 @@ Item {
             compare(map.center.latitude, 12)
         }
 
+        function test_map_visible_region()
+        {
+            mapVisibleRegion.zoomLevel = 1.0
+            wait(50)
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible1))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible2))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible3))
+
+            mapVisibleRegion.zoomLevel = 1.88
+            verify(LocationTestHelper.waitForPolished(mapVisibleRegion))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible1))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible2))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible3))
+
+            mapVisibleRegion.zoomLevel = 2.12
+            verify(LocationTestHelper.waitForPolished(mapVisibleRegion))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible1))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible2))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible3))
+
+            mapVisibleRegion.zoomLevel = 2.5
+            verify(LocationTestHelper.waitForPolished(mapVisibleRegion))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible1))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible2))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible3))
+
+            mapVisibleRegion.zoomLevel = 2.7
+            verify(LocationTestHelper.waitForPolished(mapVisibleRegion))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible1))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible2))
+            verify(mapVisibleRegion.visibleRegion.contains(coordinateVisible3))
+        }
+
         function test_map_parameters()
         {
             // coordinate is set at map element declaration