Drag and drop initiation protocol

[Rob Adams <robadams ucla edu>]

Drag and drop is a bit hard to deal with right now for window managers
that raise windows on mouse down.  This is a first crack at a protocol
to try to deal with this.

Comments appreciated, of course.

-Rob 

--- wm-spec.sgml.offic	2003-03-02 23:16:40.000000000 -0800
+++ wm-spec.sgml	2003-03-02 23:35:22.000000000 -0800
@@ -1245,6 +1245,49 @@ respond to this protocol within a reason
 See also the implementation notes on <link
linkend="KILLINGWINDOWS">killing hung processes</link>.
 		</para>
 	</sect2>
+	<sect2>
+		<title>_NET_WM_IS_DRAG_START</title>
+		<para>
+This protocol allows the Window Manager to determine if a mouse click
+in a Client window could be the beginning of a logical drag and drop
+operation.  The Client window would then respond to the query to
+inform the Window Manager whether a mouse down event at the specified
+mouse coordinates could initiate a drag and drop operation across
+applications (for example, a mouse down over a file icon in a file
+manager).  The Window Manager MAY use this information to determine
+whether it will raise the Client window on a mouse down or whether it
+will wait for a mouse up event to raise the Client.  A Client SHOULD
+indicate that it is willing to participate in this protocol by listing
+_NET_WM_IS_DRAG_START in the WM_PROTOCOLS property of the client
+window.
+		</para>
+		<para>
+A Window Manager can use this protocol at any time by sending a client
+message as follows:
+		</para>
+		<programlisting><![CDATA[
+type = ClientMessage
+window = the respective client window
+message_type = WM_PROTOCOLS
+format = 32
+data.l[0] = _NET_WM_IS_DRAG_START
+data.l[1] = timestamp
+data.l[2] = x coordinate
+data.l[3] = y coordinate
+data.l[4] = client response field
+]]></programlisting>
+		<para>
+A participating Client receiving this message MUST determine whether a
+mouse down at the specified x and y coordinates could initiate a drag
+operation, and then send the message back to the root window by
+setting window = root and setting data.l[4] to 0 if no drag
+might be initiated and data.l[4] to 1 if a drag might be initiated.
+		</para>
+		<para>
+Note that the Window Manager SHOULD avoid using the protocol unless
+the result of the returned message will change some Window Manager
behavior.
+		</para>
+	</sect2>
 </sect1>
 <sect1>
 	<title>Implementation notes</title>
(11:36PM) [readams notos ~]$ grep PING wm-spec.sgml
respond to the _NET_WM_PING protocol.
		<title>_NET_WM_PING</title>
this protocol by listing _NET_WM_PING in the WM_PROTOCOLS property of
the
data.l[0] = _NET_WM_PING
If processes fail to respond to the _NET_WM_PING protocol _NET_WM_PID
may be
Killing Hung Processes implementation note added. _NET_WM_PID and
_NET_WM_PING now link to this.
Added _NET_WM_PING protocol