package ij.gui;
import ij.*;
import java.awt.AWTEvent;

/**
* PlugIns or PlugInFilters that want to listen to changes in a GenericDialog
* without adding listeners for each dialog field should implementthis method.
* The dialogItemChanged method of a PlugIn or PlugInFilter can and should read
* the various dialog items by the appropriate GenericDialog methods like
* getNextNumber (items that are not read in the dialogItemChanged method will
* not be recorded by the Macro recorder).
*
* The PlugIn or PlugInFilter has to be added to the GenericDialog by
* its addDialogListener method:
* gd.addDialogListener(this);
*
*/
public interface DialogListener {

    /**
     * This method is invoked by a Generic Dialog if any of the inputs have changed
     *  (CANCEL does not trigger it; OK and running the dialog from a macro only
     *   trigger the first DialogListener added to a GenericDialog).
     * 
     * @param e   The event that has been generated by the user action in the dialog.
     *            Note that <code>e</code> is <code>null</code> if the
     *            dialogItemChanged method is called after the user has pressed the
     *            OK button or if the GenericDialog has read its parameters from a
     *            macro.
     * @param gd  A reference to the GenericDialog.
     * @return    Should be true if the dialog input is valid. False disables the
     *              OK button and preview (if any).
     */
    boolean dialogItemChanged(GenericDialog gd, AWTEvent e);
}
