Re: missing button release event?

[Paul Emsley <paul emsley bioch ox ac uk>]

On 10/07/12 20:33, Damon Chaplin wrote:
> On Tue, 2012-07-10 at 17:48 +0100, Paul Emsley wrote:
> > Hi,
> >
> > When I create a goocanvas
> >
> >      GtkWidget *canvas = goo_canvas_new();
> >      GooCanvas *gc = GOO_CANVAS(canvas);
> >
> > I then attached callbacks to it...
> >
> >         ... other callbacks ...
> >         g_signal_connect(G_OBJECT(goo_canvas_get_root_item(gc)),
> >                  "button_release_event",
> >                  G_CALLBACK(on_canvas_button_release), NULL);
> >
> >     This works fine almost all the time - however, there is one operation
> > (a line addition) where the on_canvas_button_release callback doesn't
> > get called (I added a print statement in it to check).  I can't think
> > why it might not be being called.  Can you help?
> >
> > Cheers,
> >
> > Paul.
> >
> > p.s. code here: http://coot.googlecode.com/svn/trunk/lbg/lbg.cc
> Are you creating an item underneath the mouse when the button is
> pressed? The button release event may be being sent to that new item and
> ignored.
>
> I can't think of any other reason at the moment. It would be handy if
> GooCanvas had some debugging support for events - i.e. output where
> events are being sent.

Hi Damon,

Thanks for your prompt reply.

Yes, I am creating an item under the mouse (at least potentially).  The 
new line (a chemical bond, FWIW) changes (or can change) the text for 
the atom (under the cursor).

I thought I had checked for that though by adding a button release 
callback specifically when text is created.  Maybe I missed one/some.  Hmm.

Why is it that for this operation the callback is attached (or is at 
least potentially attached) to the new text item, but for most other 
mouse events (motion and button-down, for example) attaching callbacks 
to the canvas works fine?

Is it more likely that the callback is attached to the text under the 
cursor that gets deleted or the text under the cursor that is newly 
created?  Maybe if I created a text group to handle this and added and 
deleted items from the group - would that be better do you think?

Cheers,

Paul.