Re: GtkEntry - did not receive focus-out-event.

[muppet <scott asofyet org>]

On Sep 21, 2005, at 10:30 PM, Daniel Kasak wrote:

> I've hit somewhat of a brick wall with the error:
>
> Gtk-WARNING **: GtkEntry - did not receive focus-out-event. If you
> connect a handler to this signal, it must return
> FALSE so the entry gets the event as well at /usr/lib/perl5/ 
> site_perl/5.8.5/Gtk2/Ex/Dialogs/Message.pm line 236.
> Gtk-ERROR **: file gtkentry.c: line 4857 (blink_cb): assertion  
> failed: (GTK_WIDGET_HAS_FOCUS (entry)) at /usr/lib/perl5/site_perl/ 
> 5.8.5/Gtk2/Ex/Dialogs/Message.pm line 236.
> Aborted
>
> which results in my app completely bailing out.

Incidentally, the reason for this is that if you inhibit the focus- 
out handler, GtkEntry has no way to disable the cursor blinking  
timeout, and the timeout subsequently runs and can cause a core dump  
because one of his pointers is invalid.  That's why they flagged this  
as a fatal error assertion.

> What's happening is that I've connected some code to run on the  
> focus-out event of an entry:
>
> sub on_Prospects_Search_LeadNo_focus_out_event {
>    my $leadno = $prospects->get_widget("Search_LeadNo")->get_text;
>    $prospect_data->query("where LeadNo=$leadno");
>    return FALSE;
> }
>
> That return FALSE bit I added just now - it didn't help any.

.... because you weren't getting that far before it blew up.  It will  
help in the future.  Read on.


> I'm getting into the line:
>
> $prospect_data->query("where LeadNo=$leadno");
>
> From here, my Gtk2::Ex::DBI module is throwing an error ( because  
> I've mucked up the SQL ... but that's my problem ) via  
> Gtk2::Ex::Dialogs. The bit of code that does this is:
>
> eval {
>    $sth->execute || die $self->{dbh}->errstr;
> };
>
> if ($@) {
>    Gtk2::Ex::Dialogs::ErrorMsg->new_and_run(
>                            title    => "Error in Query!",
>                            text    => "DB Server says:\n$@"
>    );
>    return FALSE;
> }
>
> I get the error message, but as soon as it appears, the whole app  
> crashes with the above error. What's going on? Where do I have to  
> return FALSE to stop this from happening?


This is a lot easier to understand with a timeline:

- focus into GtkEntry
  - GtkEntry installs timeout for cursor blinking
- focus out of entry
  - GtkEntry emits focus-out-event
     - your handler runs **before the default handler**.
        - your handler traps exception and creates dialog box
        - dialog box runs nested event loop
           - event processing continues, focus goes to another widget
           - entry's cursor blink timeout is still installed, and  
runs again.
             entry does not have focus, but timeout has run, so the  
widget
             is in an invalid state and calls g_error() with a  
nastygram.
     - default handler runs, uninstalls cursor blink timeout

The problem is that you're allowing the event loop to run in your  
handler for focus-out.

The solution is to get the entry's default handler to run before you  
do anything that can run a main loop.  There are two easy solutions:


a)  use signal_connect_after to have your handler run *after* the  
default handler for focus-out-event instead of before.

b)  leave the signal connected normally, but in your "catch" block,  
instead of running the dialog right then, defer it with an idle, like  
this:

    if ($@) {
        # oh, crap.  pop up the error message when the main loop is  
idle.
        Glib::Idle->add (sub {
            Gtk2::Ex::Dialogs::ErrorMsg->new_and_run(
                           title    => "Error in Query!",
                           text    => "DB Server says:\n$@"
            );
            FALSE;  # don't run again
        });
        # return control immediately.
        return FALSE;
    }


and, of course, option c) is "do both."


Hope that works.

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