Desktop: virtualise the transfer queue and the import lists

src/DodoSSH.Client.App/Views/ImportScreen.axaml

@@ -131,8 +131,20 @@
           </Grid>
         </Border>
 
-        <ScrollViewer Grid.Row="1">
-          <ItemsControl ItemsSource="{Binding Rows}" Margin="12,8">
+        <!-- Virtualised, for an inventory of hundreds of machines: see the transfer queue's own note. -->
+        <ItemsControl Grid.Row="1" ItemsSource="{Binding Rows}">
+          <ItemsControl.Template>
+            <ControlTemplate>
+              <ScrollViewer>
+                <ItemsPresenter Name="PART_ItemsPresenter" ItemsPanel="{TemplateBinding ItemsPanel}" Margin="12,8" />
+              </ScrollViewer>
+            </ControlTemplate>
+          </ItemsControl.Template>
+          <ItemsControl.ItemsPanel>
+            <ItemsPanelTemplate>
+              <VirtualizingStackPanel />
+            </ItemsPanelTemplate>
+          </ItemsControl.ItemsPanel>
             <ItemsControl.ItemTemplate>
               <DataTemplate x:DataType="vm:ImportRowViewModel">
                 <Border Classes="importrow" CornerRadius="8">
@@ -161,8 +173,7 @@
                 </Border>
               </DataTemplate>
             </ItemsControl.ItemTemplate>
-          </ItemsControl>
-        </ScrollViewer>
+        </ItemsControl>
 
       </Grid>
     </Border>