Re: Segfault with a combo with 3 columns

On Mar 26, 2007, at 8:59 PM, Daniel Kasak wrote:

I've attached a short script which produces a crash ( segfault ) for me when an item in a combo is selected.

The demo has 2 combos / models.

The 1st, 'good' model, has a Glib::Int column, and 2 Glib::String columns. This works fine.

The 2nd, 'bad' model, has a 2 Glib::Int columns, and a Glib::String column.

When an item is selected in the 2nd combo, I get a segfault. This happens if the user selects an item with the mouse, or if the item is selected in code, ie:
$widget->set_active_iter( $iter );

Note that I'm ONLY loading numeric data into the 2nd column.

My hunch is that this is a gtk+ bug, and not related to the bindings. Am I right?

Not so sure.

On one hand, you're telling the ComboBoxEntry to get the text to show in the entry from column 1, which is a Glib::Int column, and it does so, blindly trusting you, and crashing. (The crash is in strcmp(), deep within gtk_entry_set_text() from gtk_combo_box_entry_active_changed().) It's a fairly trivial patch to your code to use a real Glib::String column for the text column.

 sub create_combo {

     my $this_model = shift;

-    my $combo = Gtk2::ComboBoxEntry->new( $this_model, 1 );
+    my $combo = Gtk2::ComboBoxEntry->new( $this_model, 2 );

-    # Create a renderer for the 3rd column ( the text column )
+    # Create a renderer for the 2nd column ( the number column )
     my $renderer = Gtk2::CellRendererText->new;
     $combo->pack_start( $renderer, FALSE );
-    $combo->set_attributes( $renderer, text => 2 );
+    $combo->set_attributes( $renderer, text => 1 );

     return $combo;

On the other hand, in perl we're used to type coercion, and when dealing with GtkTreeViewColumns and GtkCellRendererTexts you get type coercion from G_TYPE_INT to G_TYPE_STRING. I've opened a gtk+ bug about it, if you'd like to follow it: show_bug.cgi?id=423201

If the monkey could type one keystroke every nanosecond, the expected waiting time until the monkey types out Hamlet is so long that the estimated age of the universe is insignificant by comparison ... this is not a practical method for writing plays.
  -- Gian-Carlo Rota

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