winutil/functions/private/Initialize-InstallAppArea.ps1

    function Initialize-InstallAppArea {
        <#
            .SYNOPSIS
                Creates a [Windows.Controls.ScrollViewer] containing a [Windows.Controls.ItemsControl] which is setup to use Virtualization to only load the visible elements for performance reasons.
                This is used as the parent object for all category and app entries on the install tab
                Used to as part of the Install Tab UI generation

            .PARAMETER TargetElement
                The element to which the AppArea shoud be added

        #>
        param($TargetElement)
        $scrollViewer = New-Object Windows.Controls.ScrollViewer
        $scrollViewer.VerticalScrollBarVisibility = 'Auto'
        $scrollViewer.HorizontalAlignment = 'Stretch'
        $scrollViewer.VerticalAlignment = 'Stretch'
        $scrollViewer.CanContentScroll = $true

        $itemsControl = New-Object Windows.Controls.ItemsControl
        $itemsControl.HorizontalAlignment = 'Stretch'
        $itemsControl.VerticalAlignment = 'Stretch'

        $itemsPanelTemplate = New-Object Windows.Controls.ItemsPanelTemplate
        $factory = New-Object Windows.FrameworkElementFactory ([Windows.Controls.VirtualizingStackPanel])
        $itemsPanelTemplate.VisualTree = $factory
        $itemsControl.ItemsPanel = $itemsPanelTemplate

        $itemsControl.SetValue([Windows.Controls.VirtualizingStackPanel]::IsVirtualizingProperty, $true)
        $itemsControl.SetValue([Windows.Controls.VirtualizingStackPanel]::VirtualizationModeProperty, [Windows.Controls.VirtualizationMode]::Recycling)

        $scrollViewer.Content = $itemsControl

        [Windows.Controls.DockPanel]::SetDock($scrollViewer, [Windows.Controls.Dock]::Bottom)
        $null = $TargetElement.Children.Add($scrollViewer)
        return $itemsControl
    }