Respect new DND options when dragging to ourselves on Haiku

* lisp/mouse.el (mouse-drag-and-drop-region): Allow dragging to
the current frame if we know `return-frame' doesn't work.
* lisp/term/haiku-win.el (haiku-dnd-drag-handler): New function.
* src/haiku_support.cc (MouseMoved): Don't send drag motion
events for the drag frame.
* src/haikuselect.c (haiku_note_drag_motion_1)
(haiku_note_drag_motion_2, haiku_note_drag_motion): New
functions.
(syms_of_haikuselect): New variable `haiku-drag-track-function'.
* src/haikuterm.c (haiku_read_socket): Note mouse motion in that
case.q
* src/haikuterm.h: Update prototypes.

lisp/mouse.el

@@ -3190,7 +3190,12 @@ is copied instead of being cut."
                                          (if mouse-drag-and-drop-region-cut-when-buffers-differ
                                              'XdndActionMove
                                            'XdndActionCopy)
-                                         (posn-window (event-end event)) 'now)
+                                         (posn-window (event-end event)) 'now
+                                         ;; On platforms where we know
+                                         ;; `return-frame' doesn't
+                                         ;; work, allow dropping on
+                                         ;; the drop frame.
+                                         (eq window-system 'haiku))
                          (quit nil))))
                   (when (framep drag-action-or-frame)
                     ;; With some window managers `x-begin-drag'

lisp/term/haiku-win.el

@@ -277,6 +277,21 @@ This is necessary because on Haiku `use-system-tooltip' doesn't
 take effect on menu items until the menu bar is updated again."
   (force-mode-line-update t))
 
+;; Note that `mouse-position' can't return the actual frame the mouse
+;; pointer is under, so this only works for the frame where the drop
+;; started.
+(defun haiku-dnd-drag-handler ()
+  "Handle mouse movement during drag-and-drop."
+  (let ((track-mouse 'drag-source)
+        (mouse-position (mouse-pixel-position)))
+    (when (car mouse-position)
+      (dnd-handle-movement (posn-at-x-y (cadr mouse-position)
+                                        (cddr mouse-position)
+                                        (car mouse-position)))
+      (redisplay))))
+
+(setq haiku-drag-track-function #'haiku-dnd-drag-handler)
+
 (defun x-begin-drag (targets &optional action frame _return-frame allow-current-frame)
   "SKIP: real doc in xfns.c."
   (unless haiku-dnd-selection-value

src/haiku_support.cc

@@ -1524,13 +1524,23 @@ public:
   MouseMoved (BPoint point, uint32 transit, const BMessage *drag_msg)
   {
     struct haiku_mouse_motion_event rq;
+    int32 windowid;
+    EmacsWindow *window;
 
+    window = (EmacsWindow *) Window ();
     rq.just_exited_p = transit == B_EXITED_VIEW;
     rq.x = point.x;
     rq.y = point.y;
-    rq.window = this->Window ();
+    rq.window = window;
     rq.time = system_time ();
-    rq.dnd_message = drag_msg != NULL;
+
+    if (drag_msg && (drag_msg->IsSourceRemote ()
+		     || drag_msg->FindInt32 ("emacs:window_id",
+					     &windowid) != B_OK
+		     || windowid != window->window_id))
+      rq.dnd_message = true;
+    else
+      rq.dnd_message = false;
 
     if (ToolTip ())
       ToolTip ()->SetMouseRelativeLocation (BPoint (-(point.x - tt_absl_pos.x),

src/haikuselect.c

@@ -791,6 +791,28 @@ ignored if it is dropped on top of FRAME.  */)
   return unbind_to (idx, Qnil);
 }
 
+static Lisp_Object
+haiku_note_drag_motion_1 (void *data)
+{
+  if (!NILP (Vhaiku_drag_track_function))
+    return call0 (Vhaiku_drag_track_function);
+
+  return Qnil;
+}
+
+static Lisp_Object
+haiku_note_drag_motion_2 (enum nonlocal_exit exit, Lisp_Object error)
+{
+  return Qnil;
+}
+
+void
+haiku_note_drag_motion (void)
+{
+  internal_catch_all (haiku_note_drag_motion_1, NULL,
+		      haiku_note_drag_motion_2);
+}
+
 void
 syms_of_haikuselect (void)
 {
@@ -800,6 +822,12 @@ Otherwise, an error will be signalled if adding a file reference to a
 system message failed.  */);
   haiku_signal_invalid_refs = true;
 
+  DEFVAR_LISP ("haiku-drag-track-function", Vhaiku_drag_track_function,
+     doc: /* If non-nil, a function to call upon mouse movement while dragging a message.
+The function is called without any arguments.  `mouse-position' can be
+used to retrieve the current position of the mouse.  */);
+  Vhaiku_drag_track_function = Qnil;
+
   DEFSYM (QSECONDARY, "SECONDARY");
   DEFSYM (QCLIPBOARD, "CLIPBOARD");
   DEFSYM (QSTRING, "STRING");

src/haikuterm.c

@@ -3155,6 +3155,9 @@ haiku_read_socket (struct terminal *terminal, struct input_event *hold_quit)
 			XSETINT (inev.y, b->y);
 			XSETFRAME (inev.frame_or_window, f);
 		      }
+		    else
+		      haiku_note_drag_motion ();
+
 		    break;
 		  }
 	      }

src/haikuterm.h

@@ -293,6 +293,7 @@ extern void haiku_put_pixel (haiku bitmap, int x, int y, unsigned long pixel);
 extern Lisp_Object haiku_menu_show (struct frame *f, int x, int y, int menu_flags,
 				    Lisp_Object title, const char **error_name);
 extern Lisp_Object haiku_popup_dialog (struct frame *f, Lisp_Object header, Lisp_Object contents);
+extern void haiku_note_drag_motion (void);
 
 extern void initialize_frame_menubar (struct frame *f);