Mostly implemented the new mockup

To add support for the new features in firmware 1.1.0, I decided to
split the Sink screen into two sections: Configuration and Power
Delivery.  The Configuration section contains all the things the Sink
screen had before, with some layout changes (notably the Save button is
part of the Configuration section, not in the HeaderBar).  The Power
Delivery section has the new features: an Output switch, which works
perfectly, and a currently half-baked Source Capabilities list item
which will eventually open a window to show the capabilities, but for
now just prints them.

data/pd-buddy-gtk.ui

                     <property name="can_focus">False</property>
                     <property name="orientation">vertical</property>
                     <child>
-                      <object class="GtkFrame">
+                      <object class="GtkBox">
                         <property name="visible">True</property>
                         <property name="can_focus">False</property>
                         <property name="halign">center</property>
-                        <property name="margin_left">50</property>
-                        <property name="margin_right">50</property>
-                        <property name="margin_top">30</property>
-                        <property name="margin_bottom">22</property>
-                        <property name="hexpand">False</property>
-                        <property name="label_xalign">0</property>
-                        <property name="shadow_type">none</property>
+                        <property name="margin_left">18</property>
+                        <property name="margin_right">18</property>
+                        <property name="margin_top">18</property>
+                        <property name="margin_bottom">18</property>
+                        <property name="orientation">vertical</property>
+                        <property name="spacing">24</property>
                         <child>
-                          <object class="GtkAlignment">
+                          <object class="GtkBox">
                             <property name="visible">True</property>
                             <property name="can_focus">False</property>
+                            <property name="orientation">vertical</property>
+                            <property name="spacing">8</property>
                             <child>
-                              <object class="GtkGrid">
+                              <object class="GtkBox">
                                 <property name="visible">True</property>
                                 <property name="can_focus">False</property>
-                                <property name="row_spacing">6</property>
-                                <property name="column_spacing">12</property>
-                                <child>
-                                  <object class="GtkLabel">
-                                    <property name="visible">True</property>
-                                    <property name="can_focus">False</property>
-                                    <property name="halign">end</property>
-                                    <property name="label" translatable="yes">Voltage</property>
-                                    <property name="justify">right</property>
-                                    <style>
-                                      <class name="dim-label"/>
-                                    </style>
-                                  </object>
-                                  <packing>
-                                    <property name="left_attach">0</property>
-                                    <property name="top_attach">0</property>
-                                  </packing>
-                                </child>
-                                <child>
-                                  <object class="GtkLabel">
-                                    <property name="visible">True</property>
-                                    <property name="can_focus">False</property>
-                                    <property name="halign">end</property>
-                                    <property name="label" translatable="yes">Current</property>
-                                    <property name="justify">right</property>
-                                    <style>
-                                      <class name="dim-label"/>
-                                    </style>
-                                  </object>
-                                  <packing>
-                                    <property name="left_attach">0</property>
-                                    <property name="top_attach">1</property>
-                                  </packing>
-                                </child>
-                                <child>
-                                  <object class="GtkSpinButton" id="current-spinbutton">
-                                    <property name="visible">True</property>
-                                    <property name="can_focus">True</property>
-                                    <property name="input_purpose">number</property>
-                                    <property name="adjustment">current-adjustment</property>
-                                    <property name="digits">2</property>
-                                    <property name="numeric">True</property>
-                                    <signal name="value-changed" handler="on_current_spinbutton_changed" swapped="no"/>
-                                  </object>
-                                  <packing>
-                                    <property name="left_attach">1</property>
-                                    <property name="top_attach">1</property>
-                                  </packing>
-                                </child>
                                 <child>
                                   <object class="GtkLabel">
                                     <property name="visible">True</property>
                                     <property name="can_focus">False</property>
                                     <property name="halign">start</property>
-                                    <property name="label" translatable="yes">A</property>
+                                    <property name="label" translatable="yes">Configuration</property>
+                                    <attributes>
+                                      <attribute name="weight" value="bold"/>
+                                    </attributes>
                                   </object>
                                   <packing>
-                                    <property name="left_attach">2</property>
-                                    <property name="top_attach">1</property>
+                                    <property name="expand">True</property>
+                                    <property name="fill">True</property>
+                                    <property name="position">0</property>
                                   </packing>
                                 </child>
                                 <child>
-                                  <object class="GtkLabel">
+                                  <object class="GtkRevealer" id="sink-save-revealer">
                                     <property name="visible">True</property>
                                     <property name="can_focus">False</property>
-                                    <property name="halign">start</property>
-                                    <property name="label" translatable="yes">V</property>
+                                    <property name="transition_type">crossfade</property>
+                                    <child>
+                                      <object class="GtkButtonBox">
+                                        <property name="visible">True</property>
+                                        <property name="can_focus">False</property>
+                                        <property name="orientation">vertical</property>
+                                        <property name="layout_style">start</property>
+                                        <child>
+                                          <object class="GtkButton" id="sink-save">
+                                            <property name="label">gtk-save</property>
+                                            <property name="visible">True</property>
+                                            <property name="can_focus">True</property>
+                                            <property name="receives_default">True</property>
+                                            <property name="use_stock">True</property>
+                                            <signal name="clicked" handler="on_sink_save_clicked" swapped="no"/>
+                                            <accelerator key="s" signal="clicked" modifiers="GDK_CONTROL_MASK"/>
+                                            <style>
+                                              <class name="suggested-action"/>
+                                            </style>
+                                          </object>
+                                          <packing>
+                                            <property name="expand">True</property>
+                                            <property name="fill">True</property>
+                                            <property name="position">0</property>
+                                          </packing>
+                                        </child>
+                                      </object>
+                                    </child>
                                   </object>
                                   <packing>
-                                    <property name="left_attach">2</property>
-                                    <property name="top_attach">0</property>
+                                    <property name="expand">False</property>
+                                    <property name="fill">True</property>
+                                    <property name="position">1</property>
                                   </packing>
                                 </child>
+                              </object>
+                              <packing>
+                                <property name="expand">False</property>
+                                <property name="fill">True</property>
+                                <property name="position">0</property>
+                              </packing>
+                            </child>
+                            <child>
+                              <object class="GtkFrame">
+                                <property name="visible">True</property>
+                                <property name="can_focus">False</property>
+                                <property name="hexpand">False</property>
+                                <property name="label_xalign">0</property>
                                 <child>
-                                  <object class="GtkComboBoxText" id="voltage-combobox">
+                                  <object class="GtkListBox" id="sink-config-list">
+                                    <property name="width_request">342</property>
                                     <property name="visible">True</property>
                                     <property name="can_focus">False</property>
-                                    <items>
-                                      <item id="voltage-five" translatable="yes">5</item>
-                                      <item id="voltage-nine" translatable="yes">9</item>
-                                      <item id="voltage-twelve" translatable="yes">12</item>
-                                      <item id="voltage-fifteen" translatable="yes">15</item>
-                                      <item id="voltage-twenty" translatable="yes">20</item>
-                                    </items>
-                                    <signal name="changed" handler="on_voltage_combobox_changed" swapped="no"/>
+                                    <property name="selection_mode">none</property>
+                                    <child>
+                                      <object class="GtkListBoxRow">
+                                        <property name="width_request">100</property>
+                                        <property name="visible">True</property>
+                                        <property name="can_focus">True</property>
+                                        <property name="vexpand">False</property>
+                                        <property name="activatable">False</property>
+                                        <child>
+                                          <object class="GtkGrid">
+                                            <property name="visible">True</property>
+                                            <property name="can_focus">False</property>
+                                            <property name="valign">center</property>
+                                            <property name="margin_left">12</property>
+                                            <property name="margin_right">6</property>
+                                            <property name="margin_top">6</property>
+                                            <property name="margin_bottom">6</property>
+                                            <property name="column_spacing">12</property>
+                                            <child>
+                                              <object class="GtkLabel">
+                                                <property name="visible">True</property>
+                                                <property name="can_focus">False</property>
+                                                <property name="halign">start</property>
+                                                <property name="hexpand">True</property>
+                                                <property name="label" translatable="yes">Voltage</property>
+                                                <property name="justify">right</property>
+                                              </object>
+                                              <packing>
+                                                <property name="left_attach">0</property>
+                                                <property name="top_attach">0</property>
+                                              </packing>
+                                            </child>
+                                            <child>
+                                              <object class="GtkComboBoxText" id="voltage-combobox">
+                                                <property name="visible">True</property>
+                                                <property name="can_focus">False</property>
+                                                <items>
+                                                  <item id="voltage-five" translatable="yes">5</item>
+                                                  <item id="voltage-nine" translatable="yes">9</item>
+                                                  <item id="voltage-twelve" translatable="yes">12</item>
+                                                  <item id="voltage-fifteen" translatable="yes">15</item>
+                                                  <item id="voltage-twenty" translatable="yes">20</item>
+                                                </items>
+                                                <signal name="changed" handler="on_voltage_combobox_changed" swapped="no"/>
+                                              </object>
+                                              <packing>
+                                                <property name="left_attach">1</property>
+                                                <property name="top_attach">0</property>
+                                              </packing>
+                                            </child>
+                                            <child>
+                                              <object class="GtkLabel">
+                                                <property name="visible">True</property>
+                                                <property name="can_focus">False</property>
+                                                <property name="halign">start</property>
+                                                <property name="label" translatable="yes">V</property>
+                                              </object>
+                                              <packing>
+                                                <property name="left_attach">2</property>
+                                                <property name="top_attach">0</property>
+                                              </packing>
+                                            </child>
+                                          </object>
+                                        </child>
+                                      </object>
+                                    </child>
+                                    <child>
+                                      <object class="GtkListBoxRow">
+                                        <property name="width_request">100</property>
+                                        <property name="visible">True</property>
+                                        <property name="can_focus">True</property>
+                                        <property name="activatable">False</property>
+                                        <child>
+                                          <object class="GtkGrid">
+                                            <property name="visible">True</property>
+                                            <property name="can_focus">False</property>
+                                            <property name="valign">center</property>
+                                            <property name="margin_left">12</property>
+                                            <property name="margin_right">6</property>
+                                            <property name="margin_top">6</property>
+                                            <property name="margin_bottom">6</property>
+                                            <property name="column_spacing">12</property>
+                                            <child>
+                                              <object class="GtkLabel">
+                                                <property name="visible">True</property>
+                                                <property name="can_focus">False</property>
+                                                <property name="halign">start</property>
+                                                <property name="hexpand">True</property>
+                                                <property name="label" translatable="yes">Current</property>
+                                                <property name="justify">right</property>
+                                              </object>
+                                              <packing>
+                                                <property name="left_attach">0</property>
+                                                <property name="top_attach">0</property>
+                                              </packing>
+                                            </child>
+                                            <child>
+                                              <object class="GtkSpinButton" id="current-spinbutton">
+                                                <property name="visible">True</property>
+                                                <property name="can_focus">True</property>
+                                                <property name="margin_left">12</property>
+                                                <property name="input_purpose">number</property>
+                                                <property name="adjustment">current-adjustment</property>
+                                                <property name="digits">2</property>
+                                                <property name="numeric">True</property>
+                                                <signal name="value-changed" handler="on_current_spinbutton_changed" swapped="no"/>
+                                              </object>
+                                              <packing>
+                                                <property name="left_attach">1</property>
+                                                <property name="top_attach">0</property>
+                                              </packing>
+                                            </child>
+                                            <child>
+                                              <object class="GtkLabel">
+                                                <property name="visible">True</property>
+                                                <property name="can_focus">False</property>
+                                                <property name="halign">start</property>
+                                                <property name="label" translatable="yes">A</property>
+                                              </object>
+                                              <packing>
+                                                <property name="left_attach">2</property>
+                                                <property name="top_attach">0</property>
+                                              </packing>
+                                            </child>
+                                          </object>
+                                        </child>
+                                      </object>
+                                    </child>
+                                    <child>
+                                      <object class="GtkListBoxRow">
+                                        <property name="width_request">100</property>
+                                        <property name="visible">True</property>
+                                        <property name="can_focus">True</property>
+                                        <property name="activatable">False</property>
+                                        <child>
+                                          <object class="GtkGrid">
+                                            <property name="visible">True</property>
+                                            <property name="can_focus">False</property>
+                                            <property name="valign">center</property>
+                                            <property name="margin_left">12</property>
+                                            <property name="margin_right">6</property>
+                                            <property name="margin_top">6</property>
+                                            <property name="margin_bottom">6</property>
+                                            <property name="column_spacing">12</property>
+                                            <child>
+                                              <object class="GtkLabel">
+                                                <property name="visible">True</property>
+                                                <property name="can_focus">False</property>
+                                                <property name="halign">start</property>
+                                                <property name="hexpand">True</property>
+                                                <property name="label" translatable="yes">Flags</property>
+                                                <property name="justify">right</property>
+                                              </object>
+                                              <packing>
+                                                <property name="left_attach">0</property>
+                                                <property name="top_attach">0</property>
+                                              </packing>
+                                            </child>
+                                            <child>
+                                              <object class="GtkButtonBox">
+                                                <property name="visible">True</property>
+                                                <property name="can_focus">False</property>
+                                                <property name="halign">start</property>
+                                                <property name="layout_style">expand</property>
+                                                <child>
+                                                  <object class="GtkToggleButton" id="giveback-toggle">
+                                                    <property name="label" translatable="yes">GiveBack</property>
+                                                    <property name="visible">True</property>
+                                                    <property name="can_focus">True</property>
+                                                    <property name="receives_default">True</property>
+                                                    <signal name="toggled" handler="on_giveback_toggle_toggled" swapped="no"/>
+                                                  </object>
+                                                  <packing>
+                                                    <property name="expand">True</property>
+                                                    <property name="fill">True</property>
+                                                    <property name="position">0</property>
+                                                  </packing>
+                                                </child>
+                                              </object>
+                                              <packing>
+                                                <property name="left_attach">1</property>
+                                                <property name="top_attach">0</property>
+                                                <property name="width">2</property>
+                                              </packing>
+                                            </child>
+                                          </object>
+                                        </child>
+                                      </object>
+                                    </child>
                                   </object>
-                                  <packing>
-                                    <property name="left_attach">1</property>
-                                    <property name="top_attach">0</property>
-                                  </packing>
                                 </child>
-                                <child>
-                                  <object class="GtkLabel">
-                                    <property name="visible">True</property>
-                                    <property name="can_focus">False</property>
-                                    <property name="halign">end</property>
-                                    <property name="label" translatable="yes">Flags</property>
-                                    <property name="justify">right</property>
-                                    <style>
-                                      <class name="dim-label"/>
-                                    </style>
-                                  </object>
-                                  <packing>
-                                    <property name="left_attach">0</property>
-                                    <property name="top_attach">2</property>
-                                  </packing>
+                                <child type="label_item">
+                                  <placeholder/>
                                 </child>
+                              </object>
+                              <packing>
+                                <property name="expand">False</property>
+                                <property name="fill">True</property>
+                                <property name="position">1</property>
+                              </packing>
+                            </child>
+                          </object>
+                          <packing>
+                            <property name="expand">False</property>
+                            <property name="fill">True</property>
+                            <property name="position">0</property>
+                          </packing>
+                        </child>
+                        <child>
+                          <object class="GtkFrame" id="power-delivery-frame">
+                            <property name="visible">True</property>
+                            <property name="can_focus">False</property>
+                            <property name="label_xalign">0</property>
+                            <property name="shadow_type">none</property>
+                            <child>
+                              <object class="GtkFrame">
+                                <property name="visible">True</property>
+                                <property name="can_focus">False</property>
+                                <property name="margin_top">6</property>
+                                <property name="margin_bottom">6</property>
+                                <property name="label_xalign">0</property>
                                 <child>
-                                  <object class="GtkButtonBox">
+                                  <object class="GtkListBox" id="power-delivery-list">
                                     <property name="visible">True</property>
                                     <property name="can_focus">False</property>
-                                    <property name="halign">start</property>
-                                    <property name="layout_style">expand</property>
+                                    <property name="selection_mode">none</property>
+                                    <signal name="row-activated" handler="on_source_cap_row_activated" swapped="no"/>
                                     <child>
-                                      <object class="GtkToggleButton" id="giveback-toggle">
-                                        <property name="label" translatable="yes">GiveBack</property>
+                                      <object class="GtkListBoxRow">
+                                        <property name="width_request">100</property>
                                         <property name="visible">True</property>
                                         <property name="can_focus">True</property>
-                                        <property name="receives_default">True</property>
-                                        <signal name="toggled" handler="on_giveback_toggle_toggled" swapped="no"/>
+                                        <property name="vexpand">False</property>
+                                        <property name="activatable">False</property>
+                                        <child>
+                                          <object class="GtkGrid">
+                                            <property name="visible">True</property>
+                                            <property name="can_focus">False</property>
+                                            <property name="valign">center</property>
+                                            <property name="margin_left">12</property>
+                                            <property name="margin_right">6</property>
+                                            <property name="margin_top">6</property>
+                                            <property name="margin_bottom">6</property>
+                                            <property name="column_spacing">12</property>
+                                            <child>
+                                              <object class="GtkLabel">
+                                                <property name="visible">True</property>
+                                                <property name="can_focus">False</property>
+                                                <property name="halign">start</property>
+                                                <property name="hexpand">True</property>
+                                                <property name="label" translatable="yes">Output</property>
+                                                <property name="justify">right</property>
+                                              </object>
+                                              <packing>
+                                                <property name="left_attach">0</property>
+                                                <property name="top_attach">0</property>
+                                              </packing>
+                                            </child>
+                                            <child>
+                                              <object class="GtkSwitch" id="output-switch">
+                                                <property name="visible">True</property>
+                                                <property name="can_focus">True</property>
+                                                <signal name="state-set" handler="on_output_switch_state_set" swapped="no"/>
+                                              </object>
+                                              <packing>
+                                                <property name="left_attach">1</property>
+                                                <property name="top_attach">0</property>
+                                                <property name="width">2</property>
+                                              </packing>
+                                            </child>
+                                          </object>
+                                        </child>
+                                      </object>
+                                    </child>
+                                    <child>
+                                      <object class="GtkListBoxRow" id="source-cap-row">
+                                        <property name="width_request">100</property>
+                                        <property name="visible">True</property>
+                                        <property name="can_focus">True</property>
+                                        <child>
+                                          <object class="GtkGrid">
+                                            <property name="visible">True</property>
+                                            <property name="can_focus">False</property>
+                                            <property name="valign">center</property>
+                                            <property name="margin_left">12</property>
+                                            <property name="margin_right">6</property>
+                                            <property name="margin_top">6</property>
+                                            <property name="margin_bottom">6</property>
+                                            <property name="column_spacing">12</property>
+                                            <child>
+                                              <object class="GtkLabel">
+                                                <property name="visible">True</property>
+                                                <property name="can_focus">False</property>
+                                                <property name="halign">start</property>
+                                                <property name="hexpand">True</property>
+                                                <property name="label" translatable="yes">Source Capabilities</property>
+                                                <property name="justify">right</property>
+                                              </object>
+                                              <packing>
+                                                <property name="left_attach">0</property>
+                                                <property name="top_attach">0</property>
+                                              </packing>
+                                            </child>
+                                            <child>
+                                              <object class="GtkLabel" id="short-source-cap-label">
+                                                <property name="visible">True</property>
+                                                <property name="can_focus">False</property>
+                                                <property name="label" translatable="yes">label</property>
+                                                <style>
+                                                  <class name="dim-label"/>
+                                                </style>
+                                              </object>
+                                              <packing>
+                                                <property name="left_attach">1</property>
+                                                <property name="top_attach">0</property>
+                                              </packing>
+                                            </child>
+                                            <child>
+                                              <object class="GtkImage">
+                                                <property name="visible">True</property>
+                                                <property name="can_focus">False</property>
+                                                <property name="icon_name">go-next-symbolic</property>
+                                              </object>
+                                              <packing>
+                                                <property name="left_attach">2</property>
+                                                <property name="top_attach">0</property>
+                                              </packing>
+                                            </child>
+                                          </object>
+                                        </child>
                                       </object>
-                                      <packing>
-                                        <property name="expand">True</property>
-                                        <property name="fill">True</property>
-                                        <property name="position">0</property>
-                                      </packing>
                                     </child>
                                   </object>
-                                  <packing>
-                                    <property name="left_attach">1</property>
-                                    <property name="top_attach">2</property>
-                                    <property name="width">2</property>
-                                  </packing>
+                                </child>
+                                <child type="label_item">
+                                  <placeholder/>
                                 </child>
                               </object>
                             </child>
+                            <child type="label">
+                              <object class="GtkLabel">
+                                <property name="visible">True</property>
+                                <property name="can_focus">False</property>
+                                <property name="label" translatable="yes">Power Delivery</property>
+                                <attributes>
+                                  <attribute name="weight" value="bold"/>
+                                </attributes>
+                              </object>
+                            </child>
                           </object>
-                        </child>
-                        <child type="label_item">
-                          <placeholder/>
+                          <packing>
+                            <property name="expand">False</property>
+                            <property name="fill">True</property>
+                            <property name="position">1</property>
+                          </packing>
                         </child>
                       </object>
                       <packing>
                 <accelerator key="Left" signal="clicked" modifiers="GDK_MOD1_MASK"/>
               </object>
             </child>
-            <child>
-              <object class="GtkRevealer" id="header-sink-save-revealer">
-                <property name="visible">True</property>
-                <property name="can_focus">False</property>
-                <property name="transition_type">crossfade</property>
-                <child>
-                  <object class="GtkButtonBox">
-                    <property name="visible">True</property>
-                    <property name="can_focus">False</property>
-                    <property name="orientation">vertical</property>
-                    <property name="layout_style">start</property>
-                    <child>
-                      <object class="GtkButton" id="header-sink-save">
-                        <property name="label">gtk-save</property>
-                        <property name="visible">True</property>
-                        <property name="can_focus">True</property>
-                        <property name="receives_default">True</property>
-                        <property name="use_stock">True</property>
-                        <signal name="clicked" handler="on_header_sink_save_clicked" swapped="no"/>
-                        <accelerator key="s" signal="clicked" modifiers="GDK_CONTROL_MASK"/>
-                        <style>
-                          <class name="suggested-action"/>
-                        </style>
-                      </object>
-                      <packing>
-                        <property name="expand">True</property>
-                        <property name="fill">True</property>
-                        <property name="position">0</property>
-                      </packing>
-                    </child>
-                  </object>
-                </child>
-              </object>
-              <packing>
-                <property name="pack_type">end</property>
-                <property name="position">1</property>
-              </packing>
-            </child>
           </object>
           <packing>
             <property name="name">page1</property>

pd-buddy-gtk.py

                 self.append(ListRowModel(port))
 
 
+def list_box_update_header_func(row, before, data):
+    """Add a separator header to all rows but the first one"""
+    if before is None:
+        row.set_header(None)
+        return
+
+    current = row.get_header()
+    if current is None:
+        current = Gtk.Separator.new(Gtk.Orientation.HORIZONTAL)
+        row.set_header(current)
+
+
 class SelectList(Gtk.Box):
     __gsignals__ = {
         'row-activated': (GObject.SIGNAL_RUN_FIRST, None,
         sl = self._builder.get_object("select-list")
 
         # Add separators to the list
-        sl.set_header_func(self._update_header_func, None)
+        sl.set_header_func(list_box_update_header_func, None)
 
         self.pack_start(self._builder.get_object("select-stack"), True, True, 0)
         self.show_all()
 
-    def _update_header_func(self, row, before, data):
-        """Add a separator header to all rows but the first one"""
-        if before is None:
-            row.set_header(None)
-            return
-
-        current = row.get_header()
-        if current is None:
-            current = Gtk.Separator.new(Gtk.Orientation.HORIZONTAL)
-            row.set_header(current)
-
     def bind_model(self, model, func):
         self._builder.get_object("select-list").bind_model(model, func)
         self._model = model
 
         self.selectlist.connect("row-activated", self.on_select_list_row_activated)
 
+        # Add separators to the configuration page lists
+        sc_list = self.builder.get_object("sink-config-list")
+        sc_list.set_header_func(list_box_update_header_func, None)
+
+        pd_list = self.builder.get_object("power-delivery-list")
+        pd_list.set_header_func(list_box_update_header_func, None)
+
     def on_pdb_window_delete_event(self, *args):
         Gtk.main_quit(*args)
 
     def on_select_list_row_activated(self, selectlist, serport):
-        # Get voltage and current widgets
+        # Get relevant widgets
         voltage = self.builder.get_object("voltage-combobox")
         current = self.builder.get_object("current-spinbutton")
         giveback = self.builder.get_object("giveback-toggle")
+        pd_frame = self.builder.get_object("power-delivery-frame")
+        output = self.builder.get_object("output-switch")
+        cap_label = self.builder.get_object("short-source-cap-label")
 
         self.serial_port = serport
 
 
         current.set_value(self.cfg.i/1000)
 
+        # Set PD frame visibility and output switch state
+        try:
+            with pdbuddy.Sink(self.serial_port) as pdbs:
+                output.set_state(pdbs.output)
+        except KeyError:
+            pd_frame.set_visible(False)
+        else:
+            pd_frame.set_visible(True)
+
+            # Update the text in the capability label
+            # TODO: do this repeatedly
+            with pdbuddy.Sink(self.serial_port) as pdbs:
+                caps = pdbs.get_source_cap()
+            cap_label.set_text('{} PDOs'.format(len(caps)))
+
         # Show the Sink page
         hst = self.builder.get_object("header-stack")
         hsink = self.builder.get_object("header-sink")
         select = self.builder.get_object("select")
         st.set_visible_child(select)
 
-    def on_header_sink_save_clicked(self, button):
+    def on_sink_save_clicked(self, button):
         window = self.builder.get_object("pdb-window")
         try:
             with pdbuddy.Sink(self.serial_port) as pdbs:
     def _set_save_button_visibility(self):
         """Show the save button if there are new settings to save"""
         # Get relevant widgets
-        rev = self.builder.get_object("header-sink-save-revealer")
+        rev = self.builder.get_object("sink-save-revealer")
 
         # Set visibility
         rev.set_reveal_child(self.cfg != self.cfg_clean)
 
         self._set_save_button_visibility()
 
+    def on_output_switch_state_set(self, switch, state):
+        with pdbuddy.Sink(self.serial_port) as pdbs:
+            pdbs.output = state
+
+    def on_source_cap_row_activated(self, box, row):
+        # Find which row was clicked
+        sc_row = self.builder.get_object("source-cap-row")
+        if row != sc_row:
+            # If it's not the source-cap-row, leave
+            return
+        # Get the source capabilities
+        with pdbuddy.Sink(self.serial_port) as pdbs:
+            caps = pdbs.get_source_cap()
+            for i, cap in enumerate(caps):
+                print("PDO {}: {}".format(i+1, cap))
+
 
 class Application(Gtk.Application):