Fix #13097: Angle snapping impossible with WGS84 projection

git-svn-id: https://josm.openstreetmap.de/svn/trunk@18612 0c6e7542-c601-0410-84e7-c038aed88b3b

Author: taylor.smock

src/org/openstreetmap/josm/actions/mapmode/DrawSnapHelper.java

@@ -24,6 +24,7 @@
 import org.openstreetmap.josm.data.osm.Node;
 import org.openstreetmap.josm.data.osm.Way;
 import org.openstreetmap.josm.data.osm.WaySegment;
+import org.openstreetmap.josm.data.projection.ProjectionRegistry;
 import org.openstreetmap.josm.gui.MainApplication;
 import org.openstreetmap.josm.gui.MapView;
 import org.openstreetmap.josm.gui.MapViewState;
@@ -439,7 +440,7 @@ public EastNorth getSnapPoint(EastNorth p) {
         double de = p.east()-e0;
         double dn = p.north()-n0;
         double l = de*pe+dn*pn;
-        double delta = MainApplication.getMap().mapView.getDist100Pixel()/20;
+        double delta = MainApplication.getMap().mapView.getDist100Pixel() / (20 * ProjectionRegistry.getProjection().getMetersPerUnit());
         if (!absoluteFix && l < delta) {
             active = false;
             return p;

test/unit/org/openstreetmap/josm/actions/mapmode/DrawSnapHelperTest.java

@@ -0,0 +1,82 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.actions.mapmode;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotSame;
+
+import java.util.Arrays;
+import java.util.stream.Stream;
+
+import javax.swing.JCheckBoxMenuItem;
+
+import org.junit.jupiter.api.extension.RegisterExtension;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.openstreetmap.josm.data.coor.EastNorth;
+import org.openstreetmap.josm.data.coor.LatLon;
+import org.openstreetmap.josm.data.osm.DataSet;
+import org.openstreetmap.josm.data.osm.Node;
+import org.openstreetmap.josm.data.osm.Way;
+import org.openstreetmap.josm.data.osm.WaySegment;
+import org.openstreetmap.josm.data.projection.Projection;
+import org.openstreetmap.josm.data.projection.ProjectionRegistry;
+import org.openstreetmap.josm.data.projection.Projections;
+import org.openstreetmap.josm.gui.MainApplication;
+import org.openstreetmap.josm.gui.layer.OsmDataLayer;
+import org.openstreetmap.josm.testutils.JOSMTestRules;
+import org.openstreetmap.josm.tools.Utils;
+
+/**
+ * Test class for {@link DrawSnapHelper}
+ */
+class DrawSnapHelperTest {
+    @RegisterExtension
+    static JOSMTestRules rule = new JOSMTestRules().projection().main();
+
+    static Stream<Arguments> testNonRegression13097() {
+        return Stream.of(
+                Arguments.of(Projections.getProjectionByCode("EPSG:4326")), // WGS84 Geographic
+                Arguments.of(Projections.getProjectionByCode("EPSG:3857")) // Mercator
+        );
+    }
+
+    /**
+     * See #13097: Angle snapping impossible with WGS84 projection
+     */
+    @ParameterizedTest
+    @MethodSource
+    void testNonRegression13097(Projection projection) {
+        ProjectionRegistry.setProjection(projection);
+        DrawAction drawAction = new DrawAction();
+        DrawSnapHelper drawSnapHelper = new DrawSnapHelper(drawAction);
+        drawSnapHelper.setMenuCheckBox(new JCheckBoxMenuItem()); // Just needed to avoid an NPE in enableSnapping
+        drawSnapHelper.init(); // Needed to get the default angle snaps
+        drawSnapHelper.enableSnapping();
+        Way way1 = new Way();
+        Node node1 = new Node(new LatLon(39.1260035, -108.5624143));
+        Node node2 = new Node(new LatLon(39.1260973, -108.5622908));
+        way1.setNodes(Arrays.asList(node1, node2));
+        DataSet ds = new DataSet();
+        ds.addPrimitiveRecursive(way1);
+        ds.setSelected(way1, node2);
+        MainApplication.getLayerManager().addLayer(new OsmDataLayer(ds, "testNonRegression13097", null));
+        // We need to ensure that the mapView is zoomed in enough. This takes several zoom in events after we zoom to node2.
+        MainApplication.getMap().mapView.zoomTo(node2);
+        for (int i = 0; i < 4; i++) {
+            MainApplication.getMap().mapView.zoomIn();
+        }
+        drawAction.enterMode();
+        drawSnapHelper.setBaseSegment(new WaySegment(way1, 0));
+        EastNorth position = projection.latlon2eastNorth(new LatLon(39.1260263, -108.5621895));
+        double wayHeading = Utils.toDegrees(
+                assertDoesNotThrow(() -> way1.firstNode().getEastNorth(projection).heading(way1.lastNode().getEastNorth()))
+        );
+        drawSnapHelper.checkAngleSnapping(position, wayHeading, wayHeading + 90);
+        EastNorth snapPoint = drawSnapHelper.getSnapPoint(position);
+        // We can't really check the latlon -- 90 degrees is different based off of projection.
+        assertNotSame(position, snapPoint, "The snap point should not be the same as the original position");
+        assertEquals(90, Math.abs(wayHeading - Utils.toDegrees(node2.getEastNorth(projection).heading(snapPoint))), 1e-8);
+    }
+}