How do I pack a Gtk::Entry into a Gtk::HeaderBar so the entry completely fills the header bar?

Question

I'm making a program in gtkmm-3.0 which has a Gtk::HeaderBar as the title bar.

I'm trying to pack a Gtk::Entry into it using this code:

Gtk::HeaderBar headerBar;
Gtk::Entry entry;

headerBar.set_hexpand();
headerBar.set_halign((Gtk::Align)GTK_ALIGN_FILL);
entry.set_hexpand();
entry.set_halign((Gtk::Align)GTK_ALIGN_FILL);
headerBar.pack_start(uriEntry);
headerBar.set_show_close_button();

The entry is correctly packed, but it only fills half the space of the header bar, which is very confusing. Using headerBar.add(entry) or headerBar.pack_end(entry) does not help the slightest (The entry still fills half the space it's supposed to take).

Also, using headerBar.pack_start() with a Gtk::Button before the headerBar.pack_start(entry) line will put the button in its place, but the entry will stop the expansion at the same point that it stopped before, being shorter than before.

How can I make the entry fill the whole header bar?

Answer 1

The problem is that Gtk::HeaderBar also has a "title" widget taking space. You could set a title, resulting in this:

An you see why only half the screen was given to the entry. One workaround is to define your own, custom, header bar. Here is an extremely minimal example:

#include <gtkmm.h>

class MainWindow : public Gtk::ApplicationWindow
{

public:

    MainWindow();

private:

    Gtk::Box m_customHeaderBar;
    Gtk::Entry m_entry;

};

MainWindow::MainWindow()
{
    m_entry.set_hexpand_set(true);
    m_entry.set_hexpand();

    m_customHeaderBar.pack_start(m_entry);

    set_titlebar(m_customHeaderBar);
}

int main(int argc, char *argv[])
{
    auto app = Gtk::Application::create(argc, argv, "org.gtkmm.examples.base");
  
    MainWindow window;
    window.show_all();
  
    return app->run(window);
}

Which results in this:

Of course, you will have to add a close button and everything yourself (I would recommend making a class). I will leave this part to you.