Maitain a collection of "hidden" views

Put the non-visible views in the new ring-list data structure so we
can pull them out in the correct order. Use this to restore the most
recently hidden view when a view is removed / closed.

lisp/group.lisp

@@ -66,25 +66,31 @@ to match."
   (declare (type mahogany-group group)
 	   (type hrt:view view))
   (with-accessors ((views mahogany-group-views)
-		   (outputs mahogany-group-output-map))
+		   (outputs mahogany-group-output-map)
+		   (hidden mahogany-group-hidden-views))
       group
     (push view (mahogany-group-views group))
     (alexandria:when-let ((current-frame (mahogany-group-current-frame group)))
+      (alexandria:when-let ((view (tree:frame-view current-frame)))
+	(ring-list:add-item hidden view))
       (setf (tree:frame-view current-frame) view))))
 
 (defun group-remove-view (group view)
   (declare (type mahogany-group group))
   (with-accessors ((view-list mahogany-group-views)
-		   (output-map mahogany-group-output-map))
+		   (output-map mahogany-group-output-map)
+		   (hidden mahogany-group-hidden-views))
       group
     (maphash (lambda (key container)
 	       (declare (ignore key))
 	       ;; OPTIMIZE ME: get-pouplated frames builds a list, we could use an iterator instead.
 	       (dolist (f (mahogany/tree:get-populated-frames (mahogany/tree:root-tree container)))
 		 (when (equalp (tree:frame-view f) view)
-		   (log-string :trace "Removing view from frame")
-		   (setf (tree:frame-view f) nil))))
+		   (setf (tree:frame-view f) nil)
+		   (alexandria:when-let ((new-view (ring-list:pop-item hidden)))
+		     (setf (tree:frame-view f) new-view)))))
 	     output-map)
+    (ring-list:remove-item hidden view)
     (setf view-list (remove view view-list :test #'equalp))))
 
 (defmethod tree:find-empty-frame ((group mahogany-group))

lisp/objects.lisp

@@ -9,6 +9,7 @@
   (number 1 :type fixnum :read-only t)
   (output-map (make-hash-table :test 'equal) :type hash-table :read-only t)
   (current-frame nil :type (or tree:frame null))
+  (hidden-views (ring-list:make-ring-list) :type ring-list:ring-list)
   (views nil :type list))
 
 (defclass mahogany-state ()

mahogany.asd

@@ -43,7 +43,7 @@
 	       			     (:file "frame" :depends-on ("tree-interface"))
 				     (:file "view" :depends-on ("tree-interface"))))
 	       (:file "package")
-	       (:file "objects" :depends-on ("package"))
+	       (:file "objects" :depends-on ("package" "ring-list"))
 	       (:file "group" :depends-on ("objects" "bindings"))
 	       (:file "state" :depends-on ("objects" "keyboard"))
 	       (:file "globals" :depends-on ("state" "objects" "system"))