🚀 go-pugleaf

This is a good notion. The Lisp machine mouse documentation window is certainly
a useful feature. As you suggest, this deserves to be implemented as a single
resource shared by all clients. Still, I think it's healthy to maintain a
conservative attitude toward protocol extensions. So, it's worthwhile
considering how the mouse doc feature could be implemented within the existing
protocol. 

Here's one approach; in fact, it follows from the suggestions in your previous
proposal. It relies upon the services of a window manager client. The basic
ideas are:

	1. The mouse doc window is created and "owned" by the window manager.

	2. Each client is responsible for displaying its own mouse doc info (if
	   any) in the mouse doc window. Although the server could know when and
	   how to do this, it is certainly true that the client itself has this
	   knowledge.

The window manager would be responsible for communicating the mouse doc window
id to each client, via a pseudo-event message.  Note that this scheme may
mandate a particular style of window manager, i.e.  one that is aware of the
initiation of client programs.  I imagine that the window manager might also
communicate a default mouse doc string, which could be redisplayed when the
client's string is removed.

As for the requisite client-side processing, I envision this as a toolkit-style
package.  The client would be responsible for selecting mouse entry/exit events
for all mouse-doc'ed windows.  The mouse doc tool would provide for registering
associations between client windows and doc string quadruples (button /modifiers
/grabbed-string /ungrabbed-string) and for preprocessing mouse entry/exit events
and displaying the correct mouse doc string (of course, such events would not be
consumed and would be passed along for further client processing).  The mouse
doc tool could also provide a special interface to grabbing/ungrabbing in order
to maintain the correct status of each window's mouse doc quadruples.

Beyond its use of standard X protocol, this approach has an additional advantage
of efficiency: no transaction between client and window manager/server processes
is needed to change the mouse doc window.  Likewise, periodic polling of the
mouse position would not be required.

However, this method does not provide for changing the mouse doc string when a
modifier key changes -- say, when the the shift key is pressed. This represents
an argument, albeit a minor one, in favor of changing the X protocol to
communicate modifier key events.