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# Putting It All Together: the `CoordDemoApplet`

The Horizon package comes with an example applet called `CoordDemoApplet` (located in the `examples/CoordDemo` directory). This applet illustrates how a dataset's metadata can be converted into an instance of `CoordinateSystem` which is then used to display coordinate positions of pixels pointed to by the mouse pointer in a display of the data. This section highlights portions of that applet, in particular, the `PosTrackerViewer` class which displays the data, to show how the coordinate and metadata classes are used to display coordinate positions.

- The Viewer: Getting and Displaying Positions
  - The `ImageDisplayMap` Class
  - Configuring the `ImageDisplayMap` Object
  - Updating the coordinate display
- The Viewable: Loading the Proper Metadata