Delivered-To: garrigue at math.nagoya-u.ac.jp
Delivered-To: lablgtk at yquem.inria.fr
Date: Fri, 21 May 2010 13:19:36 +0200
From: Maxence Guesdon <maxence.guesdon at inria.fr>
To: Alain Mebsout <Alain.Mebsout at lri.fr>
Subject: Re: [Lablgtk] Problem with Gtext.iter in menuitem callback
Message-ID: <20100521131936.1da1900b at haddock.home>
In-Reply-To: <4BF5541B.6080509 at lri.fr>
References: <4BF5541B.6080509 at lri.fr>
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Cc: lablgtk at yquem.inria.fr
Status: U

Le Thu, 20 May 2010 17:24:11 +0200,
Alain Mebsout <Alain.Mebsout@lri.fr> a =C3=A9crit :

> Hi lablgtk,
>

Hello,

> I'm trying to insert some text in a source_buffer when clicking on a=20
> menu item (in a popup menu, which shows on right clicking a certain
> tag).
>=20
> Here is a simplified version of my callback function :
>=20
> let triggers_callback (buffer:GSourceView.source_buffer) ~origin:y z
> i =3D let ni =3D new GText.iter i in
>    match GdkEvent.get_type z with
>      | `BUTTON_PRESS ->
> buffer#insert ~iter:ni " | new trigger"; (* THIS WORKS FINE *)
>          let z =3D GdkEvent.Button.cast z in
>          if GdkEvent.Button.button z =3D 3 then
>            let menu =3D GMenu.menu () in
>            let image =3D GMisc.image ~stock:`ADD () in
>            let menuitem =3D GMenu.image_menu_item
>                  ~image ~label:"Add trigger(s) ..."
> ~packing:menu#append () in
>            ignore(menuitem#connect#activate
>                      ~callback:(fun () ->
> buffer#insert ~iter:ni " | new trigger")
>                      (* GTK ERROR *)
>              );
>            menu#popup ~button:3 ~time:(GdkEvent.Button.time z);
>            true
>          else
>            false
>      | _ -> false
>=20
> The first call to buffer#insert does what it's expected to do but the=20
> second one which is connected to the menu item raises a gtk error
> (and sometimes a segfault if I try to access the iter e.g. with=20
> iter#forward_char). It looks like the iter does not exists anymore. I=20
> would be grateful if anybody could give me a hint on whether I'm
> missing something here or if there's strange magic happening in menu
> items.
>=20
> Here is the gtk error triggered by the second call to buffer#insert :
>=20
> Gtk-WARNING **: Invalid text buffer iterator: either the iterator is=20
> uninitialized, or the characters/pixbufs/widgets in the buffer have
> been modified since the iterator was created.
> You must use marks, character numbers, or line numbers to preserve a=20
> position across buffer modifications.
> You can apply tags and insert marks without invalidating your
> iterators, but any mutation that affects 'indexable' buffer contents
> (contents that can be referred to by character offset)
> will invalidate all outstanding iterators
>=20
> Gtk-CRITICAL **: gtk_text_buffer_insert: assertion=20
> `gtk_text_iter_get_buffer (iter) =3D=3D buffer' failed

As the warning says, you're using a deprecated iter. As soon as you
change the contents of the buffer, your iter is deprecated and you
must create a new one, for example from an absolute position.
You may try something like this:

after "let ni =3D new GText.iter in", add
"let offset =3D ni#offset in"

Then, where you used "ni", you can now create a new iter from the
abolute offset:
let ni =3D buffer#get_iter (`OFFSET offset) in

then use this new anv valid iter:
buffer#insert ~iter: ni ...

(this is not tested but is the general way of working with iters)

Regards,

Maxence


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