Re: [Geotools-gt2-users] Default Map Coordinates and MouseClicked

[Martin D. <mar...@te...>]

Casson Stallings a =E9crit :

> public void mouseClicked(MouseEvent event) {
>     java.awt.geom.Point2D pnt =3D null;
>     java.awt.geom.Point2D pnt2 =3D null;
>     GeoMouseEvent e =3D (GeoMouseEvent) event;
>     if (pnt !=3D null) {
>         try {
>                 pnt2 =3D e.getMapCoordinate(mapcs,pnt);
>                 jb.setText(pnt2.toString());
>             }
>         catch(TransformException te) {
>                 jb.setText("CS Transform Exception");
>                 System.err.println(te.getMessage());
>             }
>         repaint();
>         }
> }

I guess than in the above, 'getMapCoordinate' was really 'getCoordinate'=20
since the 'getMapCoordinate' method doesn't expect a CS argument.

'getCoordinate' is for getting the mouse location in some arbitrary CS,=20
which may or may not be the CS of yours data. The transformation will be=20
applied automatically as needed.

'getMapCoordinate' is for getting the mouse location in the CS used by=20
the renderer. In my understanding of what you are tring to do, all you=20
need to write is:

 > public void mouseClicked(MouseEvent event) {
 >     GeoMouseEvent e =3D (GeoMouseEvent) event;
 >     Point2D pnt =3D null;
 >     pnt =3D e.getMapCoordinate(pnt);
 >     jb.setText(pnt2.toString());
 > }

As a side note, if you want a nicer formatting of yours coordinate,=20
looks at the MouseCoordinateFormat class :).

However, the above will work only if the renderer is set to the proper=20
CS. I suggest that you try the following:

     System.out.println(renderer.getCoordinateSystem());

and verify if the renderer's CS is really the one you intented to be.

By default, the renderer is initialized with the same CS than the=20
underlying data. The problem is that current implementation of DataStore=20
in Geotools has no notion of CS, so the renderer is unable to guess what=20
the CS is and will often default to some cartesian CS, which are=20
probably not the one you wanted. The real fix is to set the DataStore's=20
CS to the one of yours data, but I don't know how to do this part (we=20
need to ask to DataStore specialists).



> 1.  Should I be setting the coordinate system to StatePlane using=20
> org.geotools.j2d.Renderer.setCoordinateSystem. If I do this just it jus=
t=20
> say what the coordinates are, or does it try to transform things?

We may try that, but I'm not sure how the renderer will react if it=20
believe that this CS is not the same one than the data CS. Is said=20
previously, the real fix is to specify the data CS, which should=20
probably be done at the DataStore level.



> 2. If I have the renderer set to a specific coordinate system, will dat=
a=20
> in other coordinate systems be automatically transformed, or do I=20
> need to build the transformation mannually?

All transformations are handled automatically, providing that the CS as=20
been set in the data of course.


> 3. If data is automatically transformed, how to I associate a coordinat=
e=20
> system with a dataset or datastore?

Thats the question! We need DataStore specialist advise here.


> 4. If I use GeoMouseEvent.getMapCoordinate(coordinate system, point) (I=
=20
> am not sure on the exact syntax.) Does this convert the coordinate from=
=20
> the Renderer map coordinates to the specified coordinate system coordin=
ates?

Yes. Note that the real syntax is:

    getCoordinate(CoordinateSystem, Point2D);

If you know that you want the data in the renderer's CS rather than an=20
arbitrary one, the following method is more convenient:

    getMapCoordinate(Point2D);

Hope its help :)

	Martin.