[STUMP] Implement drag-and-drop for windows

[Raffael Mancini]

Hi,

I'm trying to implement drag-and-drop of windows between frames. For
this I'm editing the group-button-press for tile-group.

My current version looks like this (copied mostly from float-group): 

[in tile-group.lisp]

(defmethod group-button-press ((group tile-group) x y (where window))
  (declare (ignore x y))
  (when (eq *mouse-focus-policy* :click)
    (focus-all where)
    (update-all-mode-lines))
  (when *drag-and-drop-windows*
    (let ((screen (group-screen group)))
       (multiple-value-bind (relx rely) (xlib:query-pointer
(window-parent where))
         (labels ((move-window-event-handler (&rest event-slots &key
event-key &allow-other-keys)
                    (case event-key
                      (:button-release
                       ;; Pull window from "click" to frame from "release"
                       (pull-window where (find-frame group x y))
                       :done)
                      (:motion-notify
                       (with-slots (parent) where
                         (xlib:with-state (parent)
                           (setf (xlib:drawable-x parent) (- (getf
event-slots :x) relx)
                                 (xlib:drawable-y parent) (- (getf
event-slots :y) rely))))
                       t)
                      (t
                       nil)
                      (otherwise
                       :done))))
           (xlib:grab-pointer (screen-root screen)
'(:button-release :pointer-motion))
           (unwind-protect
                (loop for ev = (xlib:process-event *display*
                                                   :handler 
#'move-window-event-handler
                                                   :timeout nil
                                                   :discard-p t)
                   until (eq ev :done))
             (ungrab-pointer)))))))

Somehow, the :button-release event never gets triggered or does not get
caught by process-event. This works in float-group though. Does anyone
know why?

Greetings!
Raffael