How to add tooltip to Gmap.Net polygon? - tooltip

Question

I'm using Gmap.net great tools for enable mapping in my .net 4 desktop application.
I'm adding polygons on form load event. But I can not set tooltip text for polygons.
any idea?

Answer 1

The only way to do it that I found is add a marker on the same overlay, and trigger its IsVisible property when the polygon is entered:
var gm = new GMapControl();
GMapOverlay polyOverlay = new GMapOverlay("polygons");
List<PointLatLng> points = new List<PointLatLng>();
points.Add(new PointLatLng(53.0, 10.0));
points.Add(new PointLatLng(53.0, 11.0));
points.Add(new PointLatLng(54.0, 11.0));
points.Add(new PointLatLng(54.0, 10.0));
var polygon = new GMapPolygon(points, "mypolygon");
polygon.Fill = new SolidBrush(Color.FromArgb(50, Color.Red));
polygon.Stroke = new Pen(Color.Red, 1);
polygon.IsHitTestVisible = true;
Controls.Add(gm);
gm.Overlays.Add(polyOverlay);
polyOverlay.Polygons.Add(polygon);
polyOverlay.Markers.Add(new GMarkerCross(new PointLatLng(53.5, 10.5)) { ToolTipText = "Test me", IsVisible = false, ToolTipMode = MarkerTooltipMode.Always });
gm.OnPolygonEnter += (poly) => polyOverlay.Markers.First().IsVisible = true;
gm.OnPolygonLeave += (poly) => polyOverlay.Markers.First().IsVisible = false;
Instead of GMarkerCross you could use a GMarkerGoogle with an empty Bitmap. Note: GMarkerGoogleType.none results in a System.ArgumentNullException when the mouse enters the polygon.

Answer 2

There is another way to add a ToolTip to a Polygon: Add a label to the form, and hide it in the Load event. Define your Polygon with a name in the usual way, and make sure to set IsHitTestVisible. Add handlers for the OnPolygonEnter and OnPolygonLeave.
Dim points As New List(Of PointLatLng)()
points.Add(New PointLatLng(48.866383, 2.323575))
points.Add(New PointLatLng(48.863868, 2.321554))
points.Add(New PointLatLng(48.861017, 2.33003))
points.Add(New PointLatLng(48.863727, 2.331918))
Dim polygon As New GMapPolygon(points, "Jardin des Tuileries")
polygon.Fill = New SolidBrush(Color.FromArgb(30, Color.Red))
polygon.Stroke = New Pen(Color.Red, 1)
polygon.IsHitTestVisible = True
ovlPolygons.Polygons.Add(polygon)
Private Sub myMap_OnPolygonEnter(item As GMapPolygon) Handles myMap.OnPolygonEnter
Label1.BringToFront()
Label1.Show()
Label1.Text = item.Name
Label1.Location = New Point(MousePosition.X - Me.Left, MousePosition.Y - Me.Top)
End Sub
Private Sub myMap_OnPolygonLeave(item As GMapPolygon) Handles myMap.OnPolygonLeave
Label1.Hide()
End Sub