/* Copyright (c) 2007 Timothy Wall, All Rights Reserved
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
* <p/>
* This library 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
* Lesser General Public License for more details.
*/
package com.sun.jna.examples.dnd;
import java.awt.AlphaComposite;
import java.awt.Component;
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.Graphics2D;
import java.awt.GraphicsConfiguration;
import java.awt.Image;
import java.awt.Point;
import java.awt.Transparency;
import java.awt.datatransfer.Transferable;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DragGestureEvent;
import java.awt.dnd.DragGestureListener;
import java.awt.dnd.DragSource;
import java.awt.dnd.DragSourceContext;
import java.awt.dnd.DragSourceDragEvent;
import java.awt.dnd.DragSourceDropEvent;
import java.awt.dnd.DragSourceEvent;
import java.awt.dnd.DragSourceListener;
import java.awt.dnd.DragSourceMotionListener;
import java.awt.dnd.DropTargetDragEvent;
import java.awt.dnd.DropTargetDropEvent;
import java.awt.dnd.DropTargetEvent;
import java.awt.dnd.InvalidDnDOperationException;
import java.awt.event.InputEvent;
import java.awt.image.BufferedImage;
import javax.swing.Icon;
import javax.swing.JColorChooser;
import javax.swing.JFileChooser;
import javax.swing.JList;
import javax.swing.JTable;
import javax.swing.JTree;
import javax.swing.text.JTextComponent;
/** Provides simplified drag handling for a component.
* Usage:<br>
* <pre><code>
* int actions = DnDConstants.MOVE_OR_COPY;
* Component component = ...;
* DragHandler handler = new DragHandler(component, actions);
* </code></pre>
* <ul>
* <li>Supports painting an arbitrary {@link Icon} with transparency to
* represent the item being dragged (restricted to the {@link java.awt.Window}
* of the drag source if the platform doesn't support drag images).
* <li>Disallow starting a drag if the user requests an unsupported action.
* <li>Adjusts the cursor on drags with no modifier for which the default action
* is disallowed but where one or more non-default actions are allowed, e.g. a
* drag (with no modifiers) to a target which supports "link" should change the
* cursor to "link" (prior to 1.6, the JRE behavior is to display a
* "not allowed" cursor, even though the action actually depends on how the
* drop target responds).
* <a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4869264">
* The bug</a> is fixed in java 1.6.
* <li>Disallow drops to targets if the non-default (user-requested) action
* is not supported by the target, e.g. the user requests a "copy" when the
* target only supports "move". This is generally the responsibility of the
* drop handler, which decides whether or not to accept a drag. The DragHandler
* provides static modifier state information since the drop handler doesn't
* have access to it.
* </ul>
* NOTE: Fundamentally, the active action is determined by the drop handler
* in {@link DropTargetDragEvent#acceptDrag}, but often client code
* simply relies on {@link DropTargetDragEvent#getDropAction}.
*/
//TODO: separate into the the following drag pieces:
// * default cursor changing behavior fix (fixed in jre1.6) (global DSL)
// * drag unselected item (fixed in 1.6, flag in 1.5.0.05+) bug not an issue w/DragHandler
// * multi-selection drag workaround (if not using swing drag gesture recognizer)
// proper multi-selection drag is provided for swing dnd as of 1.4
// (use swing drag gesture recognizer if possible?) DSL+mouse listener
//TODO: identify overlap with default Swing support + TransferHandler
// * TransferHandler doesn't have drop location information (included in 1.6)
// * SwingDropTarget allows listeners, so target highlighting is possible
//NOTE: acceptDrag(int) is simply indicates the drag is accepted; the action
// value doesn't get propagated anywhere, it's certainly not communicated to
// the drag source
//MAYBE: should Transferable/Icon provision be a separate interface
//(i.e. TransferHandler)? only if the rest of the drag handler is constant and
// only the image needs to change (for standard components, e.g. tree cells,
// table cells, etc.)
public abstract class DragHandler
implements DragSourceListener, DragSourceMotionListener, DragGestureListener {
/** Default maximum size for ghosted images. */
public static final Dimension MAX_GHOST_SIZE = new Dimension(250, 250);
/** Default transparency for ghosting. */
public static final float DEFAULT_GHOST_ALPHA = 0.5f;
/** {@link #getModifiers} returns this value when the current
* modifiers state is unknown.
*/
public static final int UNKNOWN_MODIFIERS = -1;
/** {@link #getTransferable} returns this value when
* the current {@link Transferable} is unknown.
*/
public static final Transferable UNKNOWN_TRANSFERABLE = null;
/** Convenience to reference {@link DnDConstants#ACTION_MOVE}. */
protected static final int MOVE = DnDConstants.ACTION_MOVE;
/** Convenience to reference {@link DnDConstants#ACTION_COPY}. */
protected static final int COPY = DnDConstants.ACTION_COPY;
/** Convenience to reference {@link DnDConstants#ACTION_LINK}. */
protected static final int LINK = DnDConstants.ACTION_LINK;
/** Convenience to reference {@link DnDConstants#ACTION_NONE}. */
protected static final int NONE = DnDConstants.ACTION_NONE;
// TODO: w32 explorer: link=alt or ctrl+shift, copy=ctrl or shift
// w32 others: copy=ctrl
/** Modifier mask for a user-requested move. */
static final int MOVE_MASK = InputEvent.SHIFT_DOWN_MASK;
static final boolean OSX =
System.getProperty("os.name").toLowerCase().indexOf("mac") != -1;
/** Modifier mask for a user-requested copy. */
static final int COPY_MASK =
OSX ? InputEvent.ALT_DOWN_MASK : InputEvent.CTRL_DOWN_MASK;
/** Modifier mask for a user-requested link. */
static final int LINK_MASK =
OSX ? InputEvent.ALT_DOWN_MASK|InputEvent.META_DOWN_MASK
: InputEvent.CTRL_DOWN_MASK|InputEvent.SHIFT_DOWN_MASK;
/** Modifier mask for any user-requested action. */
static final int KEY_MASK =
InputEvent.ALT_DOWN_MASK|InputEvent.META_DOWN_MASK
|InputEvent.CTRL_DOWN_MASK|InputEvent.SHIFT_DOWN_MASK
|InputEvent.ALT_GRAPH_DOWN_MASK;
private static int modifiers = UNKNOWN_MODIFIERS;
private static Transferable transferable = UNKNOWN_TRANSFERABLE;
/** Used to communicate modifier state to {@link DropHandler}. Note that
* this field will only be accurate when a {@link DragHandler} in
* the same VM started the drag. Otherwise, {@link #UNKNOWN_MODIFIERS}
* will be returned.
*/
static int getModifiers() {
return modifiers;
}
/** Used to communicate the current {@link Transferable} during a drag,
* if available. Work around absence of access to the data when dragging
* pre-1.5.
*/
public static Transferable getTransferable(DropTargetEvent e) {
if (e instanceof DropTargetDragEvent) {
try {
// getTransferable is available during drag only on 1.5+
return (Transferable)
e.getClass().getMethod("getTransferable", null).invoke(e, null);
}
catch(Exception ex) {
// Method not available
}
}
else if (e instanceof DropTargetDropEvent) {
return ((DropTargetDropEvent)e).getTransferable();
}
return transferable;
}
private int supportedActions;
private boolean fixCursor = true;
private Component dragSource;
private GhostedDragImage ghost;
private Point imageOffset;
private Dimension maxGhostSize = MAX_GHOST_SIZE;
private float ghostAlpha = DEFAULT_GHOST_ALPHA;
/** Enable drags from the given component, supporting the actions in
* the given action mask.
*/
protected DragHandler(Component dragSource, int actions) {
this.dragSource = dragSource;
this.supportedActions = actions;
try {
String alpha = System.getProperty("DragHandler.alpha");
if (alpha != null) {
try {
ghostAlpha = Float.parseFloat(alpha);
}
catch(NumberFormatException e) { }
}
String max = System.getProperty("DragHandler.maxDragImageSize");
if (max != null) {
String[] size = max.split("x");
if (size.length == 2) {
try {
maxGhostSize = new Dimension(Integer.parseInt(size[0]),
Integer.parseInt(size[1]));
}
catch(NumberFormatException e) { }
}
}
}
catch(SecurityException e) { }
// Avoid having more than one gesture recognizer active
disableSwingDragSupport(dragSource);
DragSource src = DragSource.getDefaultDragSource();
src.createDefaultDragGestureRecognizer(dragSource, supportedActions, this);
}
private void disableSwingDragSupport(Component comp) {
if (comp instanceof JTree) {
((JTree)comp).setDragEnabled(false);
}
else if (comp instanceof JList) {
((JList)comp).setDragEnabled(false);
}
else if (comp instanceof JTable) {
((JTable)comp).setDragEnabled(false);
}
else if (comp instanceof JTextComponent) {
((JTextComponent)comp).setDragEnabled(false);
}
else if (comp instanceof JColorChooser) {
((JColorChooser)comp).setDragEnabled(false);
}
else if (comp instanceof JFileChooser) {
((JFileChooser)comp).setDragEnabled(false);
}
}
/** Override to control whether a drag is started. The default
* implementation disallows the drag if the user is applying modifiers
* and the user-requested action is not supported.
*/
protected boolean canDrag(DragGestureEvent e) {
int mods = e.getTriggerEvent().getModifiersEx() & KEY_MASK;
if (mods == MOVE_MASK)
return (supportedActions & MOVE) != 0;
if (mods == COPY_MASK)
return (supportedActions & COPY) != 0;
if (mods == LINK_MASK)
return (supportedActions & LINK) != 0;
return true;
}
/** Update the modifiers hint. */
protected void setModifiers(int mods) {
modifiers = mods;
}
/** Override to provide an appropriate {@link Transferable} representing
* the data being dragged.
*/
protected abstract Transferable getTransferable(DragGestureEvent e);
/** Override this to provide a custom image. The {@link Icon}
* returned by this method by default is <code>null</code>, which results
* in no drag image.
* @param srcOffset set this to be the offset from the drag source
* component's upper left corner to the image's upper left corner.
* For example, when dragging a row from a list, the offset would be the
* row's bounding rectangle's (x,y) coordinate.<p>
* The default value is (0,0), so if unchanged, the image is will
* use the same origin as the drag source component.
*/
protected Icon getDragIcon(DragGestureEvent e, Point srcOffset) {
return null;
}
/** Override to perform any decoration of the target at the start of a drag,
* if desired.
*/
protected void dragStarted(DragGestureEvent e) { }
/** Called when a user drag gesture is recognized. This method is
* responsible for initiating the drag operation.
*/
public void dragGestureRecognized(DragGestureEvent e) {
if ((e.getDragAction() & supportedActions) != 0
&& canDrag(e)) {
setModifiers(e.getTriggerEvent().getModifiersEx() & KEY_MASK);
Transferable transferable = getTransferable(e);
if (transferable == null)
return;
try {
Point srcOffset = new Point(0, 0);
Icon icon = getDragIcon(e, srcOffset);
Point origin = e.getDragOrigin();
// offset of the image origin from the cursor
imageOffset = new Point(srcOffset.x - origin.x,
srcOffset.y - origin.y);
Icon dragIcon = scaleDragIcon(icon, imageOffset);
Cursor cursor = null;
if (dragIcon != null && DragSource.isDragImageSupported()) {
GraphicsConfiguration gc = e.getComponent().getGraphicsConfiguration();
e.startDrag(cursor, createDragImage(gc, dragIcon),
imageOffset, transferable, this);
}
else {
if (dragIcon != null) {
Point screen = dragSource.getLocationOnScreen();
screen.translate(origin.x, origin.y);
Point cursorOffset = new Point(-imageOffset.x, -imageOffset.y);
ghost = new GhostedDragImage(dragSource, dragIcon,
getImageLocation(screen), cursorOffset);
ghost.setAlpha(ghostAlpha);
}
e.startDrag(cursor, transferable, this);
}
dragStarted(e);
moved = false;
e.getDragSource().addDragSourceMotionListener(this);
DragHandler.transferable = transferable;
}
catch (InvalidDnDOperationException ex) {
if (ghost != null) {
ghost.dispose();
ghost = null;
}
}
}
}
/** Reduce the size of the given drag icon, if appropriate. When using
* a smaller drag icon, we also need to adjust the cursor offset within
* the icon.
*/
protected Icon scaleDragIcon(Icon icon, Point imageOffset) {
/*
if (icon != null && maxGhostSize != null) {
if (icon.getIconWidth() > maxGhostSize.width
|| icon.getIconHeight() > maxGhostSize.height) {
Icon scaled = new ScaledIcon(icon, maxGhostSize.width,
maxGhostSize.height);
double scale = (double)scaled.getIconWidth()/icon.getIconWidth();
imageOffset.x *= scale;
imageOffset.y *= scale;
return scaled;
}
}*/
return icon;
}
/** Create an image from the given icon. The image is provided to the
* native handler if drag images are supported natively.
*/
protected Image createDragImage(GraphicsConfiguration gc, Icon icon) {
int w = icon.getIconWidth();
int h = icon.getIconHeight();
BufferedImage image = gc.createCompatibleImage(w, h, Transparency.TRANSLUCENT);
Graphics2D g = (Graphics2D)image.getGraphics();
g.setComposite(AlphaComposite.Clear);
g.fillRect(0, 0, w, h);
// Ignore pixels in the buffered image
g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC, ghostAlpha));
icon.paintIcon(dragSource, g, 0, 0);
g.dispose();
return image;
}
/** Reduce a multiply-set bit mask to a single bit. */
private int reduce(int actions) {
if ((actions & MOVE) != 0 && actions != MOVE) {
return MOVE;
}
else if ((actions & COPY) != 0 && actions != COPY) {
return COPY;
}
return actions;
}
protected Cursor getCursorForAction(int actualAction) {
switch(actualAction) {
case MOVE:
return DragSource.DefaultMoveDrop;
case COPY:
return DragSource.DefaultCopyDrop;
case LINK:
return DragSource.DefaultLinkDrop;
default:
return DragSource.DefaultMoveNoDrop;
}
}
/** Returns the first available action supported by source and target. */
protected int getAcceptableDropAction(int targetActions) {
return reduce(supportedActions & targetActions);
}
/** Get the currently requested drop action. */
protected int getDropAction(DragSourceEvent ev) {
if (ev instanceof DragSourceDragEvent) {
DragSourceDragEvent e = (DragSourceDragEvent)ev;
return e.getDropAction();
}
if (ev instanceof DragSourceDropEvent) {
return ((DragSourceDropEvent)ev).getDropAction();
}
return NONE;
}
/** Pick a different drop action if the target doesn't support the current
* one and there are no modifiers.
*/
protected int adjustDropAction(DragSourceEvent ev) {
int action = getDropAction(ev);
if (ev instanceof DragSourceDragEvent) {
DragSourceDragEvent e = (DragSourceDragEvent)ev;
if (action == NONE) {
int mods = e.getGestureModifiersEx() & KEY_MASK;
if (mods == 0) {
action = getAcceptableDropAction(e.getTargetActions());
}
}
}
return action;
}
protected void updateCursor(DragSourceEvent ev) {
if (!fixCursor)
return;
Cursor cursor = getCursorForAction(adjustDropAction(ev));
ev.getDragSourceContext().setCursor(cursor);
}
static String actionString(int action) {
switch(action) {
case MOVE: return "MOVE";
case MOVE|COPY: return "MOVE|COPY";
case MOVE|LINK: return "MOVE|LINK";
case MOVE|COPY|LINK: return "MOVE|COPY|LINK";
case COPY: return "COPY";
case COPY|LINK: return "COPY|LINK";
case LINK: return "LINK";
default: return "NONE";
}
}
private String lastAction;
private void describe(String type, DragSourceEvent e) {
if (false) {
DragSourceContext ds = e.getDragSourceContext();
String msg = "drag: " + type;
if (e instanceof DragSourceDragEvent) {
DragSourceDragEvent ev = (DragSourceDragEvent)e;
msg += ": src=" + actionString(ds.getSourceActions())
+ " usr=" + actionString(ev.getUserAction())
+ " tgt=" + actionString(ev.getTargetActions())
+ " act=" + actionString(ev.getDropAction())
+ " mods=" + ev.getGestureModifiersEx();
}
else {
msg += ": e=" + e;
}
if (!msg.equals(lastAction)) {
System.out.println(lastAction = msg);
}
}
}
public void dragDropEnd(DragSourceDropEvent e) {
describe("end", e);
setModifiers(UNKNOWN_MODIFIERS);
transferable = UNKNOWN_TRANSFERABLE;
if (ghost != null) {
if (e.getDropSuccess()) {
ghost.dispose();
}
else {
ghost.returnToOrigin();
}
ghost = null;
}
DragSource src = e.getDragSourceContext().getDragSource();
src.removeDragSourceMotionListener(this);
moved = false;
}
private Point getImageLocation(Point where) {
where.translate(imageOffset.x, imageOffset.y);
return where;
}
public void dragEnter(DragSourceDragEvent e) {
describe("enter", e);
if (ghost != null) {
ghost.move(getImageLocation(e.getLocation()));
}
updateCursor(e);
}
// bug workaround; need to skip initial dragMouseMoved event,
// which has reports "0" for the available target actions (1.4+?)
// filed a bug for this
private boolean moved;
public void dragMouseMoved(DragSourceDragEvent e) {
describe("move", e);
if (ghost != null) {
ghost.move(getImageLocation(e.getLocation()));
}
if (moved)
updateCursor(e);
moved = true;
}
public void dragOver(DragSourceDragEvent e) {
describe("over", e);
if (ghost != null) {
ghost.move(getImageLocation(e.getLocation()));
}
updateCursor(e);
}
public void dragExit(DragSourceEvent e) {
describe("exit", e);
}
public void dropActionChanged(DragSourceDragEvent e) {
describe("change", e);
setModifiers(e.getGestureModifiersEx() & KEY_MASK);
if (ghost != null) {
ghost.move(getImageLocation(e.getLocation()));
}
updateCursor(e);
}
}