System Backdrops
Learn to use System Backdrops in Windows App SDK with this Tutorial
System Backdrops shows how you can use SystemBackdrops within the Window of an application using
the Windows App SDK.
Step 1
Follow Setup and Start on how to get Setup and Install what you need for Visual Studio 2022 and Windows App SDK.
Step 2
Then in Visual Studio within Solution Explorer for the Solution, right click on the Project shown below the Solution and then select Add then New Item…
Step 3
Then in Add New Item from the C# Items list, select Code and then select Code File from the list next to this, then type in the name of Library.cs and then Click on Add.
Step 4
You will now be in the View for the Code of Library.cs, within this type the following Code:
using Microsoft.UI.Composition;
using Microsoft.UI.Composition.SystemBackdrops;
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using System.Runtime.InteropServices;
using Windows.System;
using WinRT;
internal class Library
{
private object _queue;
private ISystemBackdropControllerWithTargets _controller;
[StructLayout(LayoutKind.Sequential)]
struct DispatcherQueueOptions
{
internal int dwSize;
internal int threadType;
internal int apartmentType;
}
[DllImport("CoreMessaging.dll")]
private static extern int CreateDispatcherQueueController(
[In] DispatcherQueueOptions options,
[In, Out, MarshalAs(UnmanagedType.IUnknown)]
ref object dispatcherQueueController);
private void EnsureDispatcherQueueController()
{
if (DispatcherQueue.GetForCurrentThread() != null)
return;
if (_queue == null)
{
DispatcherQueueOptions options;
options.dwSize = Marshal.SizeOf(typeof(DispatcherQueueOptions));
options.threadType = 2; // DQTYPE_THREAD_CURRENT
options.apartmentType = 2; // DQTAT_COM_STA
_ = CreateDispatcherQueueController(options, ref _queue);
}
}
// Set Backdrop
}
The Class that has been defined so far in Library.cs has a Member for an object and an Interface of ISystemBackdropControllerWithTargets
then there is some code to make the System Backdrops work correctly. There is a struct that will be used with the Method which will use
a DllImport for some Unmanaged Code that is part of the API for Windows to use CreateDispatcherQueueController. This is called from the
Method which will configure a DispatcherQueue which will ensure the System Backdrops work as needed of EnsureDispatcherQueueController.
Step 5
While still in the Class for Library.cs and after the Comment of // Set Backdrop type in the following Method:
public void SetBackdrop(Window window, ComboBox options)
{
if (_controller != null)
_controller.Dispose();
EnsureDispatcherQueueController();
string value = (options.SelectedItem as ComboBoxItem).Content as string;
switch (value)
{
case "Acrylic":
if (DesktopAcrylicController.IsSupported())
{
_controller = new DesktopAcrylicController();
_controller.AddSystemBackdropTarget(
window.As<ICompositionSupportsSystemBackdrop>());
_controller.SetSystemBackdropConfiguration(
new SystemBackdropConfiguration());
}
break;
case "Mica":
if (MicaController.IsSupported())
{
_controller = new MicaController();
_controller.AddSystemBackdropTarget(
window.As≶ICompositionSupportsSystemBackdrop>());
_controller.SetSystemBackdropConfiguration(
new SystemBackdropConfiguration());
}
break;
default:
_controller = null;
break;
}
}
This Method will check if ISystemBackdropControllerWithTargets has been set, or is not null then it will call the
Method for EnsureDispatcherQueueController then it will get the value from the ComboBox that was passed in,
then within a switch Statement, there is an option for Acrylic and Mica which is one of the System Backdrops
that can be supported, to check this is supported the Method of IsSupported() of the Class of DesktopAcrylicController
or MicaController is called, then the Method of AddSystemBackdropTarget and SetSystemBackdropConfiguration is
used to apply the System Backdrop with ISystemBackdropControllerWithTargets to the Window that was passed in
and the default option of the switch will set the ISystemBackdropControllerWithTargets to null.
Step 6
Step 7
In the XAML for MainWindow.xaml there will be some XAML for a StackPanel, this should be Removed:
<StackPanel Orientation="Horizontal"
HorizontalAlignment="Center" VerticalAlignment="Center">
<Button x:Name="myButton" Click="myButton_Click">Click Me</Button>
</StackPanel>
Step 8
While still in the XAML for MainWindow.xaml above </Window>, type in the following XAML:
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<ComboBox Grid.Row="0" Name="Options" Margin="25" HorizontalAlignment="Stretch"
SelectionChanged="Options_SelectionChanged">
<ComboBoxItem IsSelected="True">None</ComboBoxItem>
<ComboBoxItem>Acrylic</ComboBoxItem>
<ComboBoxItem>Mica</ComboBoxItem>
</ComboBox>
<Viewbox Grid.Row="1">
<StackPanel Spacing="5" Orientation="Horizontal"
HorizontalAlignment="Center">
<Rectangle Width="50" Height="50" Fill="Black"/>
<Rectangle Width="50" Height="50" Fill="Gray"/>
<Rectangle Width="50" Height="50" Fill="Red"/>
<Rectangle Width="50" Height="50" Fill="Orange"/>
<Rectangle Width="50" Height="50" Fill="Yellow"/>
<Rectangle Width="50" Height="50" Fill="Green"/>
<Rectangle Width="50" Height="50" Fill="Cyan"/>
<Rectangle Width="50" Height="50" Fill="Blue"/>
<Rectangle Width="50" Height="50" Fill="Magenta"/>
<Rectangle Width="50" Height="50" Fill="Purple"/>
</StackPanel>
</Viewbox>
</Grid>
This XAML features a Grid with two Rows, the first Row is for a ComboBox which contains the name of the System Backdrops and None
that will be used to apply the selected System Backdrop. The second Row is a ViewBox which is used to Scale elements and in this
is a StackPanel that contains Rectangle elements.
Step 9
Step 10
In the Code for MainWindow.xaml.cs there be a Method of myButton_Click(...) this should be Removed by removing the following:
private void myButton_Click(object sender, RoutedEventArgs e)
{
myButton.Content = "Clicked";
}
Step 11
Once myButton_Click(...) has been removed, type the following Code below the end of the Constructor of public MainWindow() { ... }:
private readonly Library _library = new();
private void Options_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
_library.SetBackdrop(this, Options);
}
The Method of Options_SelectionChanged will call the Method within Library.cs of SetBackdrop from an Instance of Library called
_library created with new() and will also pass in the current Window with the Keyword of this which will pass in the current
Instance of the Window.
Step 12
Step 13
Once running you should a Combobox with System Backdrop options and some Rectangle elements.
Step 14
You can select one of the options of Acrylic or Mica to see the System Backdrop applied to the Window or you can select None to clear the System Backdrop.
Step 15
