Linked style doesn't work for buttons

Question

Only button with label has linked style.

var button_box = new Gtk.Box (Gtk.Orientation.HORIZONTAL, 0);
button_box.get_style_context ().add_class (Gtk.STYLE_CLASS_LINKED);

info_button = new Gtk.Button.from_icon_name ("dialog-information-symbolic", Gtk.IconSize.LARGE_TOOLBAR);
button_box.add (info_button);

button_with_label = new Gtk.Button.with_label (_("Test"));
button_box.add (button_with_label);

header_bar.pack_start (button_box);

Answer 1

The Gtk.HeaderBar provides special styling for Gtk.Button's so that they look good inside it.

The solution:

In your case the solution is easy: remove the image-button style class from the info_button: info_button.get_style_context ().remove_class ("image-button");

If you have any problems with Gtk styling further on, I recommend to enable Gtk Inspector (read more here: https://wiki.gnome.org/Projects/GTK+/Inspector) which will provide you with great tools to enable / disable Gtk properties and such.