You can browse the Java source code of the oval-drawing applets, but please respect the copyright of the author, Stuart Levy (slevy@ncsa.uiuc.edu), NCSA, University of Illinois, Urbana-Champaign, October 1997.

• Curve.java (applet/standalone-program wrapper),
• CurvePanel.java (another layer of wrapper, for embedding in other applets),
• CurveDrawer.java (does all the work),

Or, pick up the source and class files in oval.tar.gz.

By default the applet offers three menu choices, but these can be extended or replaced by applet parameters. They include settings parameters, which are strings of the form:

var=value   var=value   ...

Variables you can set are:

e=number

Set eccentricity; number should be between 0 and 1.

p=number

Set parameter p, the distance weighting for Descartes ovals, or distance product for Cassini ovals. Reasonable values are from .25 to 2.5.

curve=on or curve=off

Display the curve (as a fine gray line) or don't.

slider=on or slider=off

Display the slider for adjusting p.

cassini=on or cassini=off

Display Cassini (constant-product) ovals if on, Cartesian (constant-sum) ovals (ellipses if p=1) if off.

It's not necessary to set all variables in a settings string; variables not mentioned for a menu item will be unchanged when it's selected.

Click with the right mouse button on the drawing area to display the current settings in the Java console, suitable for pasting into appropriate applet parameter strings.

The available applet parameters are:

    <PARAM NAME="settings" VALUE="initial settings string">
    <PARAM NAME="menu1" VALUE="label for first menu item">
    <PARAM NAME="settings1" VALUE="settings to apply when this item selected">
    <PARAM NAME="menu2" VALUE="label for second menu item">
    <PARAM NAME="settings2" VALUE="settings to apply when selected">

and so on, for as many menui and settingsi as desired.

By default, the standard "Ellipse"/"Cartesian"/"Cassini" menu items appear after any items specified by applet parameters. To provide a menu containing only the specified entries, provide "clearmenu" as a parameter (value doesn't matter):

  <PARAM NAME="clearmenu" VALUE="">

As an example, you could re-create the default behavior with the following parameters:

  <APPLET CODEBASE="whatever" CODE="Curve.class">
    <PARAM NAME="clearmenu" VALUE="">
    <PARAM NAME="settings" VALUE="p=1 e=.5 slider=off curve=on cassini=off">
    <PARAM NAME="menu1" VALUE="Ellipse">
    <PARAM NAME="settings1" VALUE="p=1 slider=off cassini=off">
    <PARAM NAME="menu2" VALUE="Cartesian Oval">
    <PARAM NAME="settings2" VALUE="slider=on cassini=off">
    <PARAM NAME="menu3" VALUE="Cassini Oval">
    <PARAM NAME="settings3" VALUE="slider=on cassini=on">
    message to display for non-Java browsers here...
  </APPLET>