/*
 * Created on May 31, 2005
 */
package org.flexdock.docking.floating.policy;

import org.flexdock.docking.Dockable;
import org.flexdock.docking.event.DockingEvent;

/**
 * This interface describes a set of method used to determine how floating
 * events should be handled. Classes implementing this interface should be
 * plugged into to the {@code FloatPolicyManager} to affect floating behavior of
 * the framework at runtime.
 * 
 * @author Christopher Butler
 */
public interface FloatPolicy {

    /**
     * Returns {@code true} if floating should be allowed for the specified
     * {@code Dockable}. This method will be invoked by the
     * {@code FloatPolicyManager} at the beginning of a drag operation to
     * determine whether or not floating support will be enabled for the
     * {@code Dockable} as a result of the drag. If this method returns
     * {@code false}, floating will not be allowed for the drag operation
     * against the specified {@code Dockable}.
     * 
     * @param dockable
     *            the {@code Dockable} to be checked for floating support
     * @return {@code true} if floating should be allowed for the specified
     *         {@code Dockable}; {@code false} otherwise.
     */
    boolean isFloatingAllowed(Dockable dockable);

    /**
     * Indicates whether floating should be allowed for the specified
     * {@code DockingEvent} at the end of a drag operation. The
     * {@code FloatPolicyManager} will catch all attempts to float a
     * {@code Dockable} at the end of a drag operation and invoke this method on
     * all installed {@code FloatPolicies}. If any of them returns
     * {@code false}, the docking operation will be canceled.
     * 
     * @param evt
     *            the {@code DockingEvent} to be checked for drop-to-float
     *            support
     * @return {@code true} if floating should be allowed for the specified
     *         {@code DockingEvent}; {@code false} otherwise.
     */
    boolean isFloatDropAllowed(DockingEvent evt);

    /**
     * Provides a default implementation of the FloatPolicy interface.
     * 
     * @author Christopher Butler
     */
    class NullFloatPolicy implements FloatPolicy {
        /**
         * Returns {@code true}.
         * 
         * @return {@code true}.
         * @see FloatPolicy#isFloatingAllowed(Dockable)
         */
        public boolean isFloatingAllowed(Dockable dockable) {
            return true;
        }

        /**
         * Returns {@code true}.
         * 
         * @return {@code true}.
         * @see FloatPolicy#isFloatDropAllowed(DockingEvent)
         */
        public boolean isFloatDropAllowed(DockingEvent evt) {
            return true;
        }
    }
}
