The cursor has entered the drop target boundaries.
<p>The following fields in the DropTargetEvent apply:
<ul>
<li>(in)widget
<li>(in)time
<li>(in)x
<li>(in)y
<li>(in)dataTypes
<li>(in,out)currentDataType
<li>(in)operations
<li>(in,out)detail
<li>(in,out)feedback
</ul></p>
<p>The <code>operation</code> value is determined by the modifier keys pressed by the user.
If no keys are pressed the <code>event.detail</code> field is set to DND.DROP_DEFAULT.
If the application does not set the <code>event.detail</code> to something other
than <code>DND.DROP_DEFAULT</code> the operation will be set to the platform defined standard
default.</p>
<p>The <code>currentDataType</code> is determined by the first transfer agent specified in
setTransfer() that matches a data type provided by the drag source.</p>
<p>It is possible to get a DragEnter event when the drag source does not provide any matching data.
In this case, the default operation is DND.DROP_NONE and the currentDataType is null.</p>
<p>The application can change the operation that will be performed by modifying the
<code>detail</code> field but the choice must be one of the values in the <code>operations</code>
field or DND.DROP_NONE.</p>
<p>The application can also change the type of data being requested by
modifying the <code>currentDataTypes</code> field but the value must be one of the values
in the <code>dataTypes</code> list.</p>
@param event the information associated with the drag enter event
The cursor has entered the drop target boundaries.
<p>The following fields in the DropTargetEvent apply: <ul> <li>(in)widget <li>(in)time <li>(in)x <li>(in)y <li>(in)dataTypes <li>(in,out)currentDataType <li>(in)operations <li>(in,out)detail <li>(in,out)feedback </ul></p>
<p>The <code>operation</code> value is determined by the modifier keys pressed by the user. If no keys are pressed the <code>event.detail</code> field is set to DND.DROP_DEFAULT. If the application does not set the <code>event.detail</code> to something other than <code>DND.DROP_DEFAULT</code> the operation will be set to the platform defined standard default.</p>
<p>The <code>currentDataType</code> is determined by the first transfer agent specified in setTransfer() that matches a data type provided by the drag source.</p>
<p>It is possible to get a DragEnter event when the drag source does not provide any matching data. In this case, the default operation is DND.DROP_NONE and the currentDataType is null.</p>
<p>The application can change the operation that will be performed by modifying the <code>detail</code> field but the choice must be one of the values in the <code>operations</code> field or DND.DROP_NONE.</p>
<p>The application can also change the type of data being requested by modifying the <code>currentDataTypes</code> field but the value must be one of the values in the <code>dataTypes</code> list.</p>
@param event the information associated with the drag enter event
@see DropTargetEvent