How do I change the property of a GTK widget such as a stack?

Question

I've been taking a quick look at the GTK 3.10 documentation for a GtkStack.

• https://developer.gnome.org/gtk3/3.10/GtkStack.html

It mentions that the child added to a GtkStack is given a property "icon-name".

My question is - how can I change the value of this property. The reason - I want to change the GtkStackSwitcher button to be an icon not text but I want to code this - not use a GktBuilder UI.

If you look at the gtk3-demo - Stack demo and the UI file you can see the GtkSwitcher has an icon.

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <!-- interface-requires gtk+ 3.6 -->
  <object class="GtkWindow" id="window1">
    <property name="can_focus">False</property>
    <property name="title" translatable="yes">GtkStack</property>
    <child>
      <object class="GtkGrid" id="grid1">
        <property name="visible">True</property>
        <property name="can_focus">False</property>
        <child>
          <object class="GtkStackSwitcher" id="switcher">
            <property name="visible">True</property>
            <property name="stack">stack</property>
            <property name="halign">center</property>
          </object>
          <packing>
            <property name="left_attach">0</property>
            <property name="top_attach">0</property>
            <property name="width">1</property>
            <property name="height">1</property>
          </packing>
        </child>
        <child>
          <object class="GtkStack" id="stack">
            <property name="visible">True</property>
            <property name="can_focus">True</property>
            <property name="transition-type">crossfade</property>
            <child>
              <object class="GtkImage" id="image1">
                <property name="visible">True</property>
                <property name="can_focus">False</property>
                <property name="margin-top">20</property>
                <property name="margin-bottom">20</property>
                <property name="resource">/application/gtk-logo-48.png</property>
              </object>
              <packing>
                <property name="name">page1</property>
                <property name="title" translatable="yes">Page 1</property>
              </packing>
            </child>
            <child>
              <object class="GtkCheckButton" id="checkbutton1">
                <property name="label" translatable="yes">Page 2</property>
                <property name="visible">True</property>
                <property name="can_focus">True</property>
                <property name="receives_default">False</property>
                <property name="xalign">0</property>
                <property name="draw_indicator">True</property>
                <property name="halign">center</property>
                <property name="valign">center</property>
              </object>
              <packing>
                <property name="name">page2</property>
                <property name="title" translatable="yes">Page 2</property>
              </packing>
            </child>
            <child>
              <object class="GtkSpinner" id="spinner1">
                <property name="visible">True</property>
                <property name="can_focus">False</property>
                <property name="halign">center</property>
                <property name="valign">center</property>
                <property name="active">True</property>
              </object>
              <packing>
                <property name="name">page3</property>
                <property name="icon-name">face-laugh-symbolic</property>
              </packing>
            </child>
          </object>
          <packing>
            <property name="left_attach">0</property>
            <property name="top_attach">1</property>
            <property name="width">1</property>
            <property name="height">1</property>
          </packing>
        </child>
      </object>
    </child>
  </object>
</interface>

Using the python3 interpreter under Ubuntu 14.04 (Gtk 3.10)

Python 3.4.0 (default, Apr 11 2014, 13:05:11) 
[GCC 4.8.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from gi.repository import Gtk
>>> stack = Gtk.Stack()
>>> spin = Gtk.Spinner()
>>> stack.add_named(spin, "spin")
>>> stack.show_all()
>>> child = stack.get_visible_child()
>>> child.props.icon_name = "go-previous"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'gi._gobject.GProps' object has no attribute 'icon_name'
>>> stack.props.icon_name = "go-previous"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'gi._gobject.GProps' object has no attribute 'icon_name'
>>> 

As you can see - I've added a GtkSpinner to a stack object - and I've attempted to access the child that was added and then change the property "icon-name".

No joy. So what is the obvious mistake I'm making?

Answer 1

Slight but important distinction: the icon-name isn't a "property" of the child of a GtkStack, it's a "child property" of GtkStack.

The difference is that a "child property" affects the relation between a container and one of its child widgets, rather than just the container or just the child widget.

Use this:

stack.child_set_property(child, 'icon-name', 'go-previous')