/*
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* 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
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*/
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;
}
}
}
}