/*
 *                 Sun Public License Notice
 * 
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is available at
 * http://www.sun.com/
 * 
 * The Original Code is NetBeans. The Initial Developer of the Original
 * Code is Sun Microsystems, Inc. Portions Copyright 1997-2000 Sun
 * Microsystems, Inc. All Rights Reserved.
 */

package org.openide.explorer.view;

import java.awt.Component;
import java.awt.Insets;
import java.awt.Point;
import java.awt.dnd.Autoscroll;

import javax.swing.JViewport;


/** The support for autoscrolling in components contained in
* the viewport.
*
* @author Dafe Simonek
*/
final class AutoscrollSupport extends Object
    implements Autoscroll {

    // Attributes

    /** The component which we support with autoscrolling */
    Component comp;
    /** The viewport containing asociated component */
    JViewport viewport;
    /** The insets where autoscrolling is active */
    Insets insets;
    /** Base sizes of scrolling during one autoscroll operation */
    Insets scrollUnits;
    /** Insets to return from getAutoscrollInsets - insets
    * where autoscroll could potencionally occur */
    Insets autoscrollInsets;

    /** Creates a support for given component with given insets
    * where autoscrolling is active */
    AutoscrollSupport (Component comp, Insets insets) {
        this.comp = comp;
        this.insets = insets;
        this.scrollUnits = insets;
    }

    /** Performs autoscroll operation.
    */  
    public void autoscroll (Point cursorLoc) {
        JViewport viewport = getViewport();
        if (viewport == null)
            return;
        Point viewPos = viewport.getViewPosition();
        int viewHeight = viewport.getExtentSize().height;
        int viewWidth = viewport.getExtentSize().width;
        // perform scrolling
        if ((cursorLoc.y - viewPos.y) < insets.top) {
            // scroll up
            viewport.setViewPosition(
                new Point(viewPos.x,
                          Math.max(viewPos.y - scrollUnits.top, 0)));
        } else
            if ((viewPos.y + viewHeight - cursorLoc.y) < insets.bottom) {
                // scroll down
                viewport.setViewPosition(
                    new Point(viewPos.x,
                              Math.min(viewPos.y + scrollUnits.bottom,
                                       comp.getHeight() - viewHeight)));
            } else
                if ((cursorLoc.x - viewPos.x) < insets.left) {
                    // scroll left
                    viewport.setViewPosition(
                        new Point(Math.max(viewPos.x - scrollUnits.left, 0),
                                  viewPos.y));
                } else
                    if ((viewPos.x + viewWidth - cursorLoc.x) < insets.right) {
                        // scroll right
                        viewport.setViewPosition(
                            new Point(Math.min(viewPos.x + scrollUnits.right,
                                               comp.getWidth() - viewWidth),
                                      viewPos.y));
                    }
    }

    public Insets getAutoscrollInsets () {
        if (autoscrollInsets == null) {
            int height = comp.getHeight();
            int width = comp.getWidth();
            autoscrollInsets = new Insets(height, width,
                                          height, width);
        }
        return autoscrollInsets;
    }

    /** @return insets where autoscroll is active
    */  
    public Insets getInsets () {
        return insets;
    }

    /** Sets new active autoscroll insets
    */  
    public void setInsets (Insets insets) {
        this.insets = insets;
    }

    /** @return Scroll units for one autoscroll operation.
    */  
    public Insets getScrollUnits () {
        return scrollUnits;
    }

    /** Sets autoscroll scroll units.
    * When autoscroll(..) method is called, it will scroll the
    * component accordign to scroll unit in appropriate direction.
    * So, scrollUnits.top says how much (in pixels) the component
    * will autoscroll up etc...
    */  
    public void setScrollUnits (Insets scrollUnits) {
        this.scrollUnits = scrollUnits;
    }

    /** Getter for viewport of asociated component.
    * Can return null if component is not contained in any viewport.
    */
    JViewport getViewport () {
        if (viewport == null) {
            Component curComp = comp;
            while (!(curComp instanceof JViewport) && (curComp != null)) {
                curComp = comp.getParent();
            }
            viewport = (JViewport)curComp;
        }
        return viewport;
    }

}