title: How to add an icon to a button in GTK3?
body: <p>I am using Glade to generate C-based GUI's. I have a GtkButton in my UI and would like to display an icon on it. </p>
  
  <p>In glade there seems to be an option on the General properties of the GtkButton called 'Label with optional image'. However, I can't get this to work.</p>
  
  <p>On the main() I have:</p>
  
  <pre><code>button = gtk_builder_get_object (builder, "start_button");
  button = gtk_button_new_from_icon_name ("document-new-symbolic", GTK_ICON_SIZE_BUTTON);
  </code></pre>
  
  <p>In the same folder where i run the binary file, I have a small document-new-symbolic.png. On the <a href="https://developer.gnome.org/gtk3/stable/GtkButton.html" rel="nofollow noreferrer">docs</a> it says that "If the icon name isn’t known, a “broken image” icon will be displayed instead." However, in my case, just the normal button appears without any icon.</p>
  
  <p>What is going on? Why is the icon not displayed?</p>