gtk/demos/gtk-demo/theming.ui

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <object class="GtkGrid" id="grid">
    <property name="row-spacing">10</property>
    <property name="margin-start">10</property>
    <property name="margin-end">10</property>
    <property name="margin-top">10</property>
    <property name="margin-bottom">10</property>
    <property name="orientation">vertical</property>
    <child>
      <object class="GtkBox">
        <property name="valign">center</property>
        <property name="halign">center</property>
        <style>
          <class name="linked"/>
        </style>
        <child>
          <object class="GtkButton">
            <property name="label" translatable="yes">Hi, I am a button</property>
            <property name="can-focus">1</property>
            <property name="receives-default">1</property>
          </object>
        </child>
        <child>
          <object class="GtkButton">
            <property name="label" translatable="yes">And I&apos;m another button</property>
            <property name="can-focus">1</property>
            <property name="receives-default">1</property>
          </object>
        </child>
        <child>
          <object class="GtkButton">
            <property name="label" translatable="yes">This is a button party!</property>
            <property name="can-focus">1</property>
            <property name="receives-default">1</property>
          </object>
        </child>
      </object>
    </child>
    <child>
      <object class="GtkBox">
        <property name="spacing">10</property>
        <child>
          <object class="GtkButton">
            <property name="label">Plain</property>
            <property name="halign">end</property>
            <property name="hexpand">1</property>
            <property name="vexpand">1</property>
          </object>
        </child>
        <child>
          <object class="GtkButton">
            <property name="label">Destructive</property>
            <style>
              <class name="destructive-action"/>
            </style>
          </object>
        </child>
        <child>
          <object class="GtkButton">
            <property name="label">Suggested</property>
            <style>
              <class name="suggested-action"/>
            </style>
          </object>
        </child>
      </object>
    </child>
  </object>
</interface>