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package org.eclipse.swt.dnd;
/*
* Copyright (c) 2000, 2002 IBM Corp. All rights reserved.
* This file is made available under the terms of the Common Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/cpl-v10.html
*/
import org.eclipse.swt.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.internal.*;
/**
*
* <code>DragSource</code> defines the source object for a drag and drop transfer.
*
* <p>IMPORTANT: This class is <em>not</em> intended to be subclassed.</p>
*
* <p>A drag source is the object which originates a drag and drop operation. For the specified widget,
* it defines the type of data that is available for dragging and the set of operations that can
* be performed on that data. The operations can be any bit-wise combination of DND.MOVE, DND.COPY or
* DND.LINK. The type of data that can be transferred is specified by subclasses of Transfer such as
* TextTransfer or FileTransfer. The type of data transferred can be a predefined system type or it
* can be a type defined by the application. For instructions on how to define your own transfer type,
* refer to <code>ByteArrayTransfer</code>.</p>
*
* <p>You may have several DragSources in an application but you can only have one DragSource
* per Control. Data dragged from this DragSource can be dropped on a site within this application
* or it can be dropped on another application such as an external Text editor.</p>
*
* <p>The application supplies the content of the data being transferred by implementing the
* <code>DragSourceListener</code> and associating it with the DragSource via DragSource#addDragListener.</p>
*
* <p>When a successful move operation occurs, the application is required to take the appropriate
* action to remove the data from its display and remove any associated operating system resources or
* internal references. Typically in a move operation, the drop target makes a copy of the data
* and the drag source deletes the original. However, sometimes copying the data can take a long
* time (such as copying a large file). Therefore, on some platforms, the drop target may actually
* move the data in the operating system rather than make a copy. This is usually only done in
* file transfers. In this case, the drag source is informed in the DragEnd event that a
* DROP_TARGET_MOVE was performed. It is the responsibility of the drag source at this point to clean
* up its displayed information. No action needs to be taken on the operating system resources.</p>
*
* <p> The following example shows a Label widget that allows text to be dragged from it.</p>
*
* <code><pre>
* // Enable a label as a Drag Source
* Label label = new Label(shell, SWT.NONE);
* // This example will allow text to be dragged
* Transfer[] types = new Transfer[] {TextTransfer.getInstance()};
* // This example will allow the text to be copied or moved to the drop target
* int operations = DND.DROP_MOVE | DND.DROP_COPY;
*
* DragSource source = new DragSource (label, operations);
* source.setTransfer(types);
* source.addDragListener (new DragSourceListener() {
* public void dragStart(DragSourceEvent e) {
* // Only start the drag if there is actually text in the
* // label - this text will be what is dropped on the target.
* if (label.getText().length() == 0) {
* event.doit = false;
* }
* };
* public void dragSetData (DragSourceEvent event) {
* // A drop has been performed, so provide the data of the
* // requested type.
* // (Checking the type of the requested data is only
* // necessary if the drag source supports more than
* // one data type but is shown here as an example).
* if (TextTransfer.getInstance().isSupportedType(event.dataType)){
* event.data = label.getText();
* }
* }
* public void dragFinished(DragSourceEvent event) {
* // A Move operation has been performed so remove the data
* // from the source
* if (event.detail == DND.DROP_MOVE)
* label.setText("");
* }
* });
* </pre></code>
*
*
* <dl>
* <dt><b>Styles</b></dt> <dd>DND.DROP_NONE, DND.DROP_COPY, DND.DROP_MOVE, DND.DROP_LINK</dd>
* <dt><b>Events</b></dt> <dd>DND.DragStart, DND.DragSetData, DND.DragEnd</dd>
* </dl>
*/
public final class DragSource extends Widget {
/**
* Creates a new <code>DragSource</code> to handle dragging from the specified <code>Control</code>.
* Creating an instance of a DragSource may cause system resources to be allocated depending on the platform.
* It is therefore mandatory that the DragSource instance be disposed when no longer required.
*
* @param control the <code>Control</code> that the user clicks on to initiate the drag
* @param style the bitwise OR'ing of allowed operations; this may be a combination of any of
* DND.DROP_NONE, DND.DROP_COPY, DND.DROP_MOVE, DND.DROP_LINK
*
* @exception SWTException <ul>
* <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
* <li>ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass</li>
* </ul>
*
* @see DragSource#dispose
* @see DragSource#checkSubclass
* @see DND#DROP_NONE
* @see DND#DROP_COPY
* @see DND#DROP_MOVE
* @see DND#DROP_LINK
*/
public DragSource(Control control, int style) {
super (control, style);
}
/**
* Adds the listener to the collection of listeners who will
* be notified when a drag and drop operation is in progress, by sending
* it one of the messages defined in the <code>DragSourceListener</code>
* interface.
*
* <p><ul>
* <li><code>dragStart</code> is called when the user has begun the actions required to drag the widget.
* This event gives the application the chance to decide if a drag should be started.
* <li><code>dragSetData</code> is called when the data is required from the drag source.
* <li><code>dragFinished</code> is called when the drop has successfully completed (mouse up
* over a valid target) or has been terminated (such as hitting the ESC key). Perform cleanup
* such as removing data from the source side on a successful move operation.
* </ul></p>
*
* @param listener the listener which should be notified
*
* @exception IllegalArgumentException <ul>
* <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
* </ul>
* @exception SWTException <ul>
* <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
* <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
* </ul>
*
* @see DragSourceListener
* @see #removeDragListener
* @see DragSourceEvent
*/
public void addDragListener(DragSourceListener listener) {
}
/**
* Returns the Control which is registered for this DragSource. This is the control that the
* user clicks in to initiate dragging.
*
* @return the Control which is registered for this DragSource
*/
public Control getControl () {
return null;
}
public Display getDisplay () {
return null;
}
/**
* Returns the list of data types that can be transferred by this DragSource.
*
* @return the list of data types that can be transferred by this DragSource
*/
public Transfer[] getTransfer(){
return null;
}
/**
* Removes the listener from the collection of listeners who will
* be notified when a drag and drop operation is in progress.
*
* @param listener the listener which should be notified
*
* @exception IllegalArgumentException <ul>
* <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
* </ul>
* @exception SWTException <ul>
* <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
* <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
* </ul>
*
* @see DragSourceListener
* @see #addDragListener
*/
public void removeDragListener(DragSourceListener listener) {
}
/**
* Specifies the list of data types that can be transferred by this DragSource.
* The application must be able to provide data to match each of these types when
* a successful drop has occurred.
*
* @param transferAgents a list of Transfer objects which define the types of data that can be
* dragged from this source
*/
public void setTransfer(Transfer[] transferAgents){
}
}
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