To: tim at fungible.com
Cc: lablgtk at kaba.or.jp
Subject: Re: Can't get keypresses from a GMisc.drawing_area
In-Reply-To: <20020809181226.61C9E7F66 at lobus.fungible.com>
References: <20020809123807R.garrigue at kurims.kyoto-u.ac.jp>
	<20020809045034.996707F66@lobus.fungible.com>
	<20020809181226.61C9E7F66@lobus.fungible.com>
Mime-Version: 1.0
Content-Type: Text/Plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Message-Id: <20020819115555F.garrigue at kurims.kyoto-u.ac.jp>
Date: Mon, 19 Aug 2002 11:55:55 +0900
From: Jacques Garrigue <garrigue at kurims.kyoto-u.ac.jp>
Lines: 101

From: tim@fungible.com (Tim Freeman)
> From: Jacques Garrigue <garrigue@kurims.kyoto-u.ac.jp>
> >You can only get keypress events on the toplevel window.
> >i.e. area#misc#toplevel
> 
> Well, not quite.  area#misc#toplevel is a GObj.widget option.
> There doesn't seem to be any path from GObj.widget to a key_press method.
> 
> In C GTK programs, the method that gives you a toplevel gives you a
> widget, and then you can inspect its type and downcast it to a
> window.  OCAML doesn't let you downcast.

You can, but you must go through he Gtk* interface.
For instance, GtkWindow.Window.cast safely casts (potentially raising
an exception) from a 'a obj to a window obj, which you can wrap
afterwards:
     new GWindow.window (GtkWindow.Window.cast w#as_widget)

However, in the present case, the spec of misc#toplevel was wrong.
It always returns the topmost parent, and the widget itself if it is
not available. As a result you cannot be sure it will be a window.

So, here is a better patch, which adds the GWindow.toplevel function to
give you the toplevel window of a widget, if it exists.

---------------------------------------------------------------------------
Jacques Garrigue      Kyoto University     garrigue at kurims.kyoto-u.ac.jp
		<A HREF=http://wwwfun.kurims.kyoto-u.ac.jp/~garrigue/>JG</A>


Index: src/gObj.ml
===================================================================
RCS file: /staff2/garrigue/repos/lablgtk/src/gObj.ml,v
retrieving revision 1.41
diff -u -r1.41 gObj.ml
--- src/gObj.ml	2002/06/20 00:17:08	1.41
+++ src/gObj.ml	2002/08/19 02:35:55
@@ -275,8 +275,8 @@
   (* get functions *)
   method name = Widget.get_name obj
   method toplevel =
-    try Some (new widget (Object.unsafe_cast (Widget.get_toplevel obj)))
-    with Gpointer.Null -> None
+    try new widget (Object.unsafe_cast (Widget.get_toplevel obj))
+    with Gpointer.Null -> failwith "GObj.misc_ops#toplevel"
   method window = Widget.window obj
   method colormap = Widget.get_colormap obj
   method visual = Widget.get_visual obj
Index: src/gObj.mli
===================================================================
RCS file: /staff2/garrigue/repos/lablgtk/src/gObj.mli,v
retrieving revision 1.37
diff -u -r1.37 gObj.mli
--- src/gObj.mli	2002/06/20 00:17:08	1.37
+++ src/gObj.mli	2002/08/19 02:34:24
@@ -186,7 +186,7 @@
     method show : unit -> unit
     method show_all : unit -> unit
     method style : style
-    method toplevel : widget option
+    method toplevel : widget
     method unmap : unit -> unit
     method unparent : unit -> unit
     method unrealize : unit -> unit
Index: src/gWindow.ml
===================================================================
RCS file: /staff2/garrigue/repos/lablgtk/src/gWindow.ml,v
retrieving revision 1.21
diff -u -r1.21 gWindow.ml
--- src/gWindow.ml	2001/03/12 03:43:42	1.21
+++ src/gWindow.ml	2002/08/19 02:40:15
@@ -46,6 +46,12 @@
   if show then Widget.show w;
   new window w
 
+let cast_window (w : #widget) =
+  new window (GtkWindow.Window.cast w#as_widget)
+
+let toplevel (w : #widget) =
+  try Some (cast_window w#misc#toplevel) with Cannot_cast _ -> None
+
 class dialog obj = object
   inherit [window] window_skel (obj : Gtk.dialog obj)
   method connect = new container_signals obj
Index: src/gWindow.mli
===================================================================
RCS file: /staff2/garrigue/repos/lablgtk/src/gWindow.mli,v
retrieving revision 1.21
diff -u -r1.21 gWindow.mli
--- src/gWindow.mli	2002/05/30 05:49:09	1.21
+++ src/gWindow.mli	2002/08/19 02:43:14
@@ -49,6 +49,9 @@
   ?border_width:int ->
   ?width:int -> ?height:int -> ?show:bool -> unit -> window
 
+val toplevel : #widget -> window option
+(** return the toplevel window of this widget, if existing *)
+
 class dialog : Gtk.dialog obj ->
   object
     inherit [window] window_skel