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	/*
	* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package sun.awt;

	import java.awt.ScrollPane;
	import java.awt.Insets;
	import java.awt.Adjustable;
	import java.awt.event.MouseWheelEvent;

	import sun.util.logging.PlatformLogger;

	/*
	* ScrollPaneWheelScroller is a helper class for implmenenting mouse wheel
	* scrolling on a java.awt.ScrollPane. It contains only static methods.
	* No objects of this class may be instantiated, thus it is declared abstract.
	*/
	public abstract class ScrollPaneWheelScroller {

	private static final PlatformLogger log = PlatformLogger.getLogger("sun.awt.ScrollPaneWheelScroller");

	private ScrollPaneWheelScroller() {}

	/*
	* Called from ScrollPane.processMouseWheelEvent()
	*/
	public static void handleWheelScrolling(ScrollPane sp, MouseWheelEvent e) {
	if (log.isLoggable(PlatformLogger.Level.FINER)) {
	log.finer("x = " + e.getX() + ", y = " + e.getY() + ", src is " + e.getSource());
	}
	int increment = 0;

	if (sp != null && e.getScrollAmount() != 0) {
	Adjustable adj = getAdjustableToScroll(sp);
	if (adj != null) {
	increment = getIncrementFromAdjustable(adj, e);
	if (log.isLoggable(PlatformLogger.Level.FINER)) {
	log.finer("increment from adjustable(" + adj.getClass() + ") : " + increment);
	}
	scrollAdjustable(adj, increment);
	}
	}
	}

	/*
	* Given a ScrollPane, determine which Scrollbar should be scrolled by the
	* mouse wheel, if any.
	*/
	public static Adjustable getAdjustableToScroll(ScrollPane sp) {
	int policy = sp.getScrollbarDisplayPolicy();

	// if policy is display always or never, use vert
	if (policy == ScrollPane.SCROLLBARS_ALWAYS \|\|
	policy == ScrollPane.SCROLLBARS_NEVER) {
	if (log.isLoggable(PlatformLogger.Level.FINER)) {
	log.finer("using vertical scrolling due to scrollbar policy");
	}
	return sp.getVAdjustable();

	}
	else {

	Insets ins = sp.getInsets();
	int vertScrollWidth = sp.getVScrollbarWidth();

	if (log.isLoggable(PlatformLogger.Level.FINER)) {
	log.finer("insets: l = " + ins.left + ", r = " + ins.right +
	", t = " + ins.top + ", b = " + ins.bottom);
	log.finer("vertScrollWidth = " + vertScrollWidth);
	}

	// Check if scrollbar is showing by examining insets of the
	// ScrollPane
	if (ins.right >= vertScrollWidth) {
	if (log.isLoggable(PlatformLogger.Level.FINER)) {
	log.finer("using vertical scrolling because scrollbar is present");
	}
	return sp.getVAdjustable();
	}
	else {
	int horizScrollHeight = sp.getHScrollbarHeight();
	if (ins.bottom >= horizScrollHeight) {
	if (log.isLoggable(PlatformLogger.Level.FINER)) {
	log.finer("using horiz scrolling because scrollbar is present");
	}
	return sp.getHAdjustable();
	}
	else {
	if (log.isLoggable(PlatformLogger.Level.FINER)) {
	log.finer("using NO scrollbar becsause neither is present");
	}
	return null;
	}
	}
	}
	}

	/*
	* Given the info in a MouseWheelEvent and an Adjustable to scroll, return
	* the amount by which the Adjustable should be adjusted. This value may
	* be positive or negative.
	*/
	public static int getIncrementFromAdjustable(Adjustable adj,
	MouseWheelEvent e) {
	if (log.isLoggable(PlatformLogger.Level.FINE)) {
	if (adj == null) {
	log.fine("Assertion (adj != null) failed");
	}
	}

	int increment = 0;

	if (e.getScrollType() == MouseWheelEvent.WHEEL_UNIT_SCROLL) {
	increment = e.getUnitsToScroll() * adj.getUnitIncrement();
	}
	else if (e.getScrollType() == MouseWheelEvent.WHEEL_BLOCK_SCROLL) {
	increment = adj.getBlockIncrement() * e.getWheelRotation();
	}
	return increment;
	}

	/*
	* Scroll the given Adjustable by the given amount. Checks the Adjustable's
	* bounds and sets the new value to the Adjustable.
	*/
	public static void scrollAdjustable(Adjustable adj, int amount) {
	if (log.isLoggable(PlatformLogger.Level.FINE)) {
	if (adj == null) {
	log.fine("Assertion (adj != null) failed");
	}
	if (amount == 0) {
	log.fine("Assertion (amount != 0) failed");
	}
	}

	int current = adj.getValue();
	int upperLimit = adj.getMaximum() - adj.getVisibleAmount();
	if (log.isLoggable(PlatformLogger.Level.FINER)) {
	log.finer("doScrolling by " + amount);
	}

	if (amount > 0 && current < upperLimit) { // still some room to scroll
	// down
	if (current + amount < upperLimit) {
	adj.setValue(current + amount);
	return;
	}
	else {
	adj.setValue(upperLimit);
	return;
	}
	}
	else if (amount < 0 && current > adj.getMinimum()) { // still some room
	// to scroll up
	if (current + amount > adj.getMinimum()) {
	adj.setValue(current + amount);
	return;
	}
	else {
	adj.setValue(adj.getMinimum());
	return;
	}
	}
	}
	}

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