Making a GtkLabel in Glade fill the width - gtk

Question

In Glade (version 3.8.5 as I am targetting gtk 2.24), I have created a label that sits in a row of a vbox. I have set the background color of the label (in Attributes) to blue, and the label appears to fill the entire row. But the blue background only extends as far as the text extent, not the entire width of the label.
How can I make the blue bar extend to the edges of the panel?

Answer 1

I read a while ago that Gtk labels don't actually have a color of their own, but they take whatever color their background widget has. I don't remember the source of this piece of information, but I do remember the solution, which is to put the label in a Gtk EventBox and change the color of said EventBox. I tested this solution in my gtk project with good results.
This is the function I use to change the color of the EventBox, by the way I'm using slightly older versions of Gtk and Glade, and I'm using C++ so if you're working with C you'll have to find the C equivalents of every function:
void GuiUtil::changeColor(Gtk::Widget* widget, double r, double g, double b) {
Glib::RefPtr<Gdk::Colormap> colormap = widget->get_colormap();
Glib::RefPtr<Gtk::Style> style = widget->get_style()->copy();
// STATE_NORMAL (most of the time)
{
Gdk::Color color;
color.set_rgb_p(r,g,b);
colormap->alloc_color(color);
style->set_bg(Gtk::STATE_NORMAL, color);
}
// STATE_PRELIGHT (when mouse hovers)
{
Gdk::Color color;
color.set_rgb_p(r*0.9,g*0.9,b*0.9);
colormap->alloc_color(color);
style->set_bg(Gtk::STATE_PRELIGHT, color);
}
// STATE_ACTIVE (when clicked)
{
Gdk::Color color;
color.set_rgb_p(r*0.8,g*0.8,b*0.8);
colormap->alloc_color(color);
style->set_bg(Gtk::STATE_ACTIVE, color);
}
widget->set_style(style);
}
As far as I know there isn't a way of doing this with Glade only.