Drag-n-drop + CAPI + OS X

I'm writing a CAPI application that will mostly be used on OS X.  I'd
really like to enable drag-and-drop support, since most OS X users expect
to be able to drag and drop things around.

I have no problem getting drag-n-drop to work in a pure Objective-C application,
but when I try to apply the same principles to my CAPI application, it simply
doesn't work.  I've discussed this a little with LispWorks support, but
drag-n-drop continues to elude me.

In an Objective-C application, I can write:

    [textField registerForDraggedTypes:
           [NSArray arrayWithObjects: NSStringPboardType,
    NSFilenamesPboardType, nil]];

and that text field will then accept strings and dropped files.  I
tried to do the equivalent operation in CAPI:

    ;; from Raffael Cavallaro
    (defmacro @ (&body body) `(objc:invoke ,@body))

    (let* ((pane (contain (make-instance 'text-input-pane)))
           (representation (slot-value (capi-internals:representation
    pane) 'cc-lib::main-view)))
     (@ representation "registerForDraggedTypes:"
       (@ "NSArray" "arrayWithObject:" (cocoa:ns-string-pboard-type)))
     representation)

but the text-input-pane displayed doesn't accept text or filenames.
Also, as soon as any object is dragged over the window, it starts
to lag a little as I move it around.  But in any case, the
text-input-pane doesn't accept the text or show the little drag icon
like the Cocoa field in the snippet above.  (as a side-question, does
anyone  have an example of LispWorks
code calling arrayWithObjects: ?  Passing each object as an argument
doesn't work,
nor does passing a list of the objects as one argument).

I also tried a slightly more complicated approach, but got the same
results as above (lag while dragging, no icon displayed, item slides
back to its source when I release the mouse).  The code is below.

I also tried delivering all of these code snippets, thinking that
maybe the IDE was doing something to affect dropping; I got the same
behavior.

I realize I'm sort of breaking the rules by dealing with CAPI
representations directly, but if there is some simple thing I could do
to get this started (some Cocoa setting that LispWorks changes, for
example), I think I'd be able to fill in the rest.

Here is the code I mentioned above:

------
(defpackage :drag-n-drop (:use :cl :capi))
(in-package :drag-n-drop)

(defmacro @ (&body body) `(objc:invoke ,@body))

(defvar *bang* nil)

(defconstant +ns-dragging-operation-copy+ 2)

(objc:define-objc-method ("draggingEntered:" (:unsigned :int))
   ((self capi-cocoa-library::output-pane-representation)
    (sender objc:objc-object-pointer))
 (declare (ignore sender))
 (push 'dragging-entered *bang*)
 +ns-dragging-operation-copy+)

(let* ((pane (contain (make-instance 'output-pane)))
       (representation (slot-value (capi-internals:representation
pane) 'cc-lib::main-view)))
  (@ representation "registerForDraggedTypes:"
     (@ "NSArray" "arrayWithObject:" (cocoa:ns-string-pboard-type)))
     representation)

------

When this code runs, I get the behavior described above, and the
value of *BANG* never changes from its initial NIL (so the draggingEntered:
message is never sent).

As another data point, this last snippet exhibits the same behavior as the
examples above (that is, *bang* doesn't change, the image lags as it's
dragged through the window, the drag icon doesn't change to a + sign,
and the dragged item slides back to its source if the mouse is
released).

------
(objc:define-objc-class foo ()
 ()
 (:objc-class-name "FooView")
 (:objc-superclass-name "NSView"))

(objc:define-objc-method ("draggingEntered:" (:unsigned :int))
   ((self foo)
    (sender objc:objc-object-pointer))
 (declare (ignore sender))
 (push *bang* 'dragging-entered)
 +ns-dragging-operation-copy+)

(let* ((pane (contain (make-instance 'cocoa-view-pane :view-class "FooView")))
      (representation (slot-value (capi-internals:representation
pane) 'cc-lib::main-view)))
 (@ representation "registerForDraggedTypes:"
   (@ "NSArray" "arrayWithObject:" (cocoa:ns-string-pboard-type)))
 representation)
------

I would appreciate any help at all in getting this to work.  Drag and drop
is essential to this application, and if I can't get it to work I'll have
to resort to something painful and drastic like writing a pure-Cocoa
application.

Bill Atkins