root/data/resources/ui/window.ui

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <template class="ExampleApplicationWindow" parent="AdwApplicationWindow">
    <property name="width-request">360</property>
    <property name="height-request">294</property>
    <child>
        <object class="AdwBreakpoint" id="wide">
          <condition>min-width: 800sp</condition>
        </object>
      </child>
    <child>
      <object class="AdwBreakpoint" id="narrow">
        <condition>max-width: 800sp</condition>
        <setter object="browse" property="narrow">True</setter>
      </object>
    </child>
    <child>
      <object class="AdwToastOverlay" id="toast">
        <child>
          <object class="GtkStack" id="stack">
            <child>
              <object class="GtkStackPage">
                <property name="name">browse</property>
                <property name="title">Browse</property>
                <property name="child">
                  <object class="BrowsePage" id="browse">
                  </object>
                </property>
              </object>
            </child>

            <child>
              <object class="GtkStackPage">
                <property name="name">wiki</property>
                <property name="title">wiki</property>

                <property name="child">
                  <object class="WikiPage" id="wiki">
                    <property name="narrow" bind-source="browse" bind-property="narrow" bind-flags="sync-create">False</property>
                  </object>
                </property>
              </object>
            </child>

          </object>
        </child>
      </object>
    </child>
  </template>
</interface>