1. Entering/Leaving Top Level Windows

When the pointer enters a new top level window, the initiator notifies the receiver with a XmTOP_LEVEL_ENTER message.

Table: The XmTOP_LEVEL_ENTER message send by the initiator.

Message User Data	Size	Description
data.b[0]	BYTE	Reason: XmTOP_LEVEL_ENTER (0x00)
data.b[1]	BYTE	Byte Order: either 'B' (MSB first) or 'l' (LSB first).
data.b[2..3]	CARD16	(DnD Flags: unused)
data.b[4..7]	CARD32	Timestamp: set to the timestamp of the corresponding X event triggering this message.
data.b[8..11]	CARD32	Source Window: source window ID of the initiator.
data.b[12..15]	CARD32	Drag Initiator Info Atom: atom ID of a property the initiator set up when it started the drag or drop operation.

The atom ID (in table

it is called the ``Drag Initiator Info Atom'') sent in the XmTOP_LEVEL_ENTER drag message is a selection atom. It must be unique for the duration of the Drag & Drop transaction. In addition, the initiator must own the selection and must be ready to convert data from the early beginning of the drag operation, since the receiver can ask for a conversion dynamically during the drag to validate the operation.

When the pointer leaves a top level window, the initiator notifies the receiver with a XmTOP_LEVEL_LEAVE message.

Table: The XmTOP_LEVEL_LEAVE message send by the initiator.

Message User Data	Size	Description
data.b[0]	BYTE	Reason: XmTOP_LEVEL_LEAVE (0x01)
data.b[1]	BYTE	Byte Order: either 'B' (MSB first) or 'l' (LSB first).
data.b[2..3]	CARD16	(DnD Flags: unused)
data.b[4..7]	CARD32	Timestamp: set to the timestamp of the corresponding X event triggering this message.

A receiver never replies (echoes) the XmTOP_LEVEL_ENTER and XmTOP_LEVEL_LEAVE messages.