/*
* @(#)BasicDropTargetListener.java 1.10 03/12/19
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package javax.swing.plaf.basic;
import java.awt.*;
import java.awt.dnd.*;
import javax.swing.*;
import javax.swing.plaf.UIResource;
import java.awt.event.*;
import javax.swing.Timer;
/**
* The Swing DropTarget implementation supports multicast notification
* to listeners, so this implementation is used as an additional
* listener that extends the primary drop target functionality
* (i.e. linkage to the TransferHandler) to include autoscroll and
* establish an insertion point for the drop. This is used by the ComponentUI
* of components supporting a selection mechanism, which have a
* way of indicating a location within their model.
* <p>
* The autoscroll functionality is based upon the Swing scrolling mechanism
* of the Scrollable interface. The unit scroll increment is used to as
* the scroll amount, and the scrolling is based upon JComponent.getVisibleRect
* and JComponent.scrollRectToVisible. The band of area around the visible
* rectangle used to invoke autoscroll is based upon the unit scroll increment
* as that is assumed to represent the last possible item in the visible region.
* <p>
* The subclasses are expected to implement the following methods to manage the
* insertion location via the components selection mechanism.
* <ul>
* <li>saveComponentState
* <li>restoreComponentState
* <li>restoreComponentStateForDrop
* <li>updateInsertionLocation
* </ul>
*
* @author Timothy Prinzing
* @version 1.10 12/19/03
*/
class BasicDropTargetListener implements DropTargetListener, UIResource, ActionListener {
/**
* construct a DropTargetAutoScroller
* <P>
* @param c the <code>Component</code>
* @param p the <code>Point</code>
*/
protected BasicDropTargetListener() {
}
/**
* called to save the state of a component in case it needs to
* be restored because a drop is not performed.
*/
protected void saveComponentState(JComponent c) {
}
/**
* called to restore the state of a component in case a drop
* is not performed.
*/
protected void restoreComponentState(JComponent c) {
}
/**
* called to restore the state of a component in case a drop
* is performed.
*/
protected void restoreComponentStateForDrop(JComponent c) {
}
/**
* called to set the insertion location to match the current
* mouse pointer coordinates.
*/
protected void updateInsertionLocation(JComponent c, Point p) {
}
private static final int AUTOSCROLL_INSET = 10;
/**
* Update the geometry of the autoscroll region. The geometry is
* maintained as a pair of rectangles. The region can cause
* a scroll if the pointer sits inside it for the duration of the
* timer. The region that causes the timer countdown is the area
* between the two rectangles.
* <p>
* This is implemented to use the visible area of the component
* as the outer rectangle, and the insets are fixed at 10. Should
* the component be smaller than a total of 20 in any direction,
* autoscroll will not occur in that direction.
*/
void updateAutoscrollRegion(JComponent c) {
// compute the outer
Rectangle visible = c.getVisibleRect();
outer.reshape(visible.x, visible.y, visible.width, visible.height);
// compute the insets
Insets i = new Insets(0, 0, 0, 0);
if (c instanceof Scrollable) {
int minSize = 2 * AUTOSCROLL_INSET;
if (visible.width >= minSize) {
i.left = i.right = AUTOSCROLL_INSET;
}
if (visible.height >= minSize) {
i.top = i.bottom = AUTOSCROLL_INSET;
}
}
// set the inner from the insets
inner.reshape(visible.x + i.left,
visible.y + i.top,
visible.width - (i.left + i.right),
visible.height - (i.top + i.bottom));
}
/**
* Perform an autoscroll operation. This is implemented to scroll by the
* unit increment of the Scrollable using scrollRectToVisible. If the
* cursor is in a corner of the autoscroll region, more than one axis will
* scroll.
*/
void autoscroll(JComponent c, Point pos) {
if (c instanceof Scrollable) {
Scrollable s = (Scrollable) c;
if (pos.y < inner.y) {
// scroll upward
int dy = s.getScrollableUnitIncrement(outer, SwingConstants.VERTICAL, -1);
Rectangle r = new Rectangle(inner.x, outer.y - dy, inner.width, dy);
c.scrollRectToVisible(r);
} else if (pos.y > (inner.y + inner.height)) {
// scroll downard
int dy = s.getScrollableUnitIncrement(outer, SwingConstants.VERTICAL, 1);
Rectangle r = new Rectangle(inner.x, outer.y + outer.height, inner.width, dy);
c.scrollRectToVisible(r);
}
if (pos.x < inner.x) {
// scroll left
int dx = s.getScrollableUnitIncrement(outer, SwingConstants.HORIZONTAL, -1);
Rectangle r = new Rectangle(outer.x - dx, inner.y, dx, inner.height);
c.scrollRectToVisible(r);
} else if (pos.x > (inner.x + inner.width)) {
// scroll right
int dx = s.getScrollableUnitIncrement(outer, SwingConstants.HORIZONTAL, 1);
Rectangle r = new Rectangle(outer.x + outer.width, inner.y, dx, inner.height);
c.scrollRectToVisible(r);
}
}
}
/**
* Initializes the internal properties if they haven't been already
* inited. This is done lazily to avoid loading of desktop properties.
*/
private void initPropertiesIfNecessary() {
if (timer == null) {
Toolkit t = Toolkit.getDefaultToolkit();
Integer initial = new Integer(100);
Integer interval = new Integer(100);
try {
initial = (Integer)t.getDesktopProperty(
"DnD.Autoscroll.initialDelay");
} catch (Exception e) {
// ignore
}
try {
interval = (Integer)t.getDesktopProperty(
"DnD.Autoscroll.interval");
} catch (Exception e) {
// ignore
}
timer = new Timer(interval.intValue(), this);
timer.setCoalesce(true);
timer.setInitialDelay(initial.intValue());
try {
hysteresis = ((Integer)t.getDesktopProperty(
"DnD.Autoscroll.cursorHysteresis")).intValue();
} catch (Exception e) {
// ignore
}
}
}
static JComponent getComponent(DropTargetEvent e) {
DropTargetContext context = e.getDropTargetContext();
return (JComponent) context.getComponent();
}
// --- ActionListener methods --------------------------------------
/**
* The timer fired, perform autoscroll if the pointer is within the
* autoscroll region.
* <P>
* @param e the <code>ActionEvent</code>
*/
public synchronized void actionPerformed(ActionEvent e) {
updateAutoscrollRegion(component);
if (outer.contains(lastPosition) && !inner.contains(lastPosition)) {
autoscroll(component, lastPosition);
}
}
// --- DropTargetListener methods -----------------------------------
public void dragEnter(DropTargetDragEvent e) {
component = getComponent(e);
TransferHandler th = component.getTransferHandler();
canImport = th.canImport(component, e.getCurrentDataFlavors());
if (canImport) {
saveComponentState(component);
lastPosition = e.getLocation();
updateAutoscrollRegion(component);
initPropertiesIfNecessary();
}
}
public void dragOver(DropTargetDragEvent e) {
if (canImport) {
Point p = e.getLocation();
updateInsertionLocation(component, p);
// check autoscroll
synchronized(this) {
if (Math.abs(p.x - lastPosition.x) > hysteresis ||
Math.abs(p.y - lastPosition.y) > hysteresis) {
// no autoscroll
if (timer.isRunning()) timer.stop();
} else {
if (!timer.isRunning()) timer.start();
}
lastPosition = p;
}
}
}
public void dragExit(DropTargetEvent e) {
if (canImport) {
restoreComponentState(component);
}
cleanup();
}
public void drop(DropTargetDropEvent e) {
if (canImport) {
restoreComponentStateForDrop(component);
}
cleanup();
}
public void dropActionChanged(DropTargetDragEvent e) {
}
/**
* Cleans up internal state after the drop has finished (either succeeded
* or failed).
*/
private void cleanup() {
if (timer != null) {
timer.stop();
}
component = null;
lastPosition = null;
}
// --- fields --------------------------------------------------
private Timer timer;
private Point lastPosition;
private Rectangle outer = new Rectangle();
private Rectangle inner = new Rectangle();
private int hysteresis = 10;
private boolean canImport;
/**
* The current component. The value is cached from the drop events and used
* by the timer. When a drag exits or a drop occurs, this value is cleared.
*/
private JComponent component;
}
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