mac.diff

diff --git a/platform/macos/app/MapDocument.m b/platform/macos/app/MapDocument.m
index 42398ff..2f96522 100644
--- a/platform/macos/app/MapDocument.m
+++ b/platform/macos/app/MapDocument.m
@@ -99,6 +99,37 @@ NS_ARRAY_OF(id <MGLAnnotation>) *MBXFlattenedShapes(NS_ARRAY_OF(id <MGLAnnotatio
     [self.mapView addGestureRecognizer:pressGestureRecognizer];

     [self applyPendingState];
+
+    [self performSelector:@selector(addTestShape) withObject:nil afterDelay:1];
+}
+
+- (void)addTestShape {
+    CLLocationCoordinate2D center = self.mapView.centerCoordinate;
+    CLLocationCoordinate2D lineCoordinates[2] = {
+        CLLocationCoordinate2DMake(45, -122),
+        center
+    };
+    MGLPolyline *line = [MGLPolyline polylineWithCoordinates:lineCoordinates count:2];
+    [self.mapView addAnnotation:line];
+}
+
+- (void)mapView:(MGLMapView *)mapView cameraDidChangeAnimated:(BOOL)animated {
+//    update tail coordinate
+//    CLLocationCoordinate2D center = mapView.centerCoordinate;
+//    MGLPolyline *line = (MGLPolyline *)mapView.annotations.firstObject;
+//    CLLocationCoordinate2D *coordinates = malloc(2 * sizeof(CLLocationCoordinate2D));
+//    [line getCoordinates:coordinates range:NSMakeRange(0, 2)];
+//    coordinates[1] = center;
+//    [line setCoordinates:coordinates range:NSMakeRange(0, 2)];
+//    free(coordinates);
+
+    // append coordinate to tail
+    CLLocationCoordinate2D center = mapView.centerCoordinate;
+    MGLPolyline *line = (MGLPolyline *)mapView.annotations.firstObject;
+    CLLocationCoordinate2D *coordinates = malloc(1 * sizeof(CLLocationCoordinate2D));
+    coordinates[0] = center;
+    [line setCoordinates:coordinates range:NSMakeRange(line.pointCount, 1)];
+    free(coordinates);
 }

 - (NSWindow *)window {