So I've been trying to get a System.Windows.Window to be aligned with a control in a second Window . In the image, the magnifying glass is the control I want to align to. There's padding around the icon. The dark gray box with the +- buttons is the Window . I want it to appear like the left side of that image. But I commonly get what's on the right—if the gray window even appears. I know the window with the +- buttons is open as it's modal and top level. But I can't see it. Below is the code I use to position it. The gray window has its WindowsStartupLocation set to Manual . Among the things I tried include setting only the Left or Top properties. Setting only Left gives me something resembling what I see in the right pane. If I set Top with or without setting Left , the gray window never appears. System.Windows.Point ptWhere = ctrlOpenedBy.PointToScreen(new System.Windows.Point(0, 0)); Left = ptWhere.X; Top = ptWhere.Y - ActualHeight; So what am I doing wrong?

Ah, System.Windows.DpiScale and `System.Windows.Media.VisualTreeHelper`` to the rescue. What was suggested above almost worked. However, I had to divide by the scale—not multiple it in.

How to align a WPF window to a child of a second window?

Accepted answer

Hui Liu-MSFT 48,571 Microsoft Vendor

Hi,@Will Pittenger . Welcome to Microsoft Q&A. To position GrayWindow so that its left side aligns with the left side of the ctrlOpenedBy image and its bottom edge aligns with the top edge of the ctrlOpenedBy image, you need to adjust the Left and Top properties of GrayWindow based on the image's position and dimensions. Here is my test sample, you could check it out.


<Window x:Class="WindowInWindow.GrayWindow"

       ...  
       WindowStyle="None"  Background="Gray" Topmost="False"    Title="GrayWindow" Height="100" Width="400">
    <StackPanel Orientation="Horizontal">
        <Button x:Name="minmize" Width="30" Height="50" Content="-"/>
        <Image Source="OIP.jpg" Width="80" Height="50"/>
        <Button x:Name="addbutton" Width="30" Height="50" Content="+"/>
    </StackPanel>
</Window>

<Window x:Class="WindowInWindow.MainWindow"
   ...
   Loaded="Window_Loaded"  Title="MainWindow" Height="450" Width="800">
<Grid Name="grid" Background="Pink">
    <StackPanel Orientation="Horizontal" HorizontalAlignment="Left" VerticalAlignment="Bottom">
        <Image x:Name="ctrlOpenedBy" Source="th.jpg" Width="40" Height="40"  />
        <TextBlock Text="search" Width="100" Height="40" FontSize="22" TextAlignment="Center" Background="AliceBlue"/>
    </StackPanel>
</Grid>
</Window>

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    ShowGrayWindow();
}
private void ShowGrayWindow()
{
    GrayWindow grayWindow = new GrayWindow();
    grayWindow.WindowStartupLocation = WindowStartupLocation.Manual;
    grayWindow.Owner = this;
    grayWindow.Loaded += (s, e) =>
    {
        Point imagePosition = ctrlOpenedBy.PointToScreen(new Point(0, 0));
        grayWindow.Left = imagePosition.X;
        grayWindow.Top = imagePosition.Y - grayWindow.ActualHeight ;

    };
    grayWindow.Show();
}

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Will Pittenger 306 Reputation points

2024-08-08T09:09:16.1666667+00:00

I'm trying to make everything self contained in the gray window. But otherwise, what I have already resembles what you mentioned.
Will Pittenger 306 Reputation points

2024-08-08T09:11:49.7533333+00:00

Currently, my code uses OnActivated. Should I switch to another event?

Hui Liu-MSFT 48,571 Microsoft Vendor

Hi,@Will Pittenger .

If you want to make your GrayWindow self-contained and manage its own positioning relative to the ctrlOpenedBy image, you can consider using the OnActivated event to set its position. However, it's generally better to use the Loaded event because the ActualHeight property is guaranteed to have a valid value at that point.

Loaded Event: This event is fired when the window is fully loaded and rendered, making it a reliable time to set the position based on the ActualHeight.

Activated Event: This event is fired when the window becomes active. If the window is activated after being shown, it might not yet be fully rendered, which could lead to issues if you rely on the ActualHeight in this event.

Method1:

private Image _controlOpenedBy;

 public GrayWindow(Image controlOpenedBy)

 {

     InitializeComponent();

     _controlOpenedBy = controlOpenedBy; // Pass the control reference

 }

 protected override void OnActivated(EventArgs e)

 {

     base.OnActivated(e);

     // Get the position of the image in screen coordinates

     Point imagePosition = _controlOpenedBy.PointToScreen(new Point(0, 0));

     // Set the window position

     this.Left = imagePosition.X;

     this.Top = imagePosition.Y - this.ActualHeight; // Align the bottom edge

 }

ShowGrayWindow:

  private void ShowGrayWindow()
  {
      GrayWindow grayWindow = new GrayWindow(ctrlOpenedBy); // Pass the reference
      grayWindow.WindowStartupLocation = WindowStartupLocation.Manual;
      grayWindow.Owner = this;
      grayWindow.Show();
  }

Method2:


public partial class GrayWindow : Window
{

    public GrayWindow()
    {

        InitializeComponent();
    this.Loaded += Window_Loaded;
    }
    private double _leftPosition;
    private double _topPosition;

    public GrayWindow(double left, double top)
    {
        InitializeComponent();

        _leftPosition = left;

        _topPosition = top;
    }
    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        Left = _leftPosition;

        Top = _topPosition - this.ActualHeight;

    }
}

ShowGrayWindow:

 private void ShowGrayWindow()
 {
     Point imagePosition = ctrlOpenedBy.PointToScreen(new Point(0, 0));

     // Create GrayWindow with position data
     GrayWindow grayWindow = new GrayWindow(imagePosition.X, imagePosition.Y);
     grayWindow.WindowStartupLocation = WindowStartupLocation.Manual;
     grayWindow.Owner = this;
     grayWindow.Show();
 }

Will Pittenger 306 Reputation points

2024-08-08T13:40:37.9966667+00:00

I'd try it, but when I changed one of my windows to derive from a custom base class, the XAML compiler decided the x:Name attribute is invalid on root item. I need that so some bindings work. So the project isn't compiling currently.
Will Pittenger 306 Reputation points

2024-08-08T13:41:41.0933333+00:00

You might make that a new answer.
Will Pittenger 306 Reputation points

2024-08-08T17:01:56.4933333+00:00

Well, I found a work around. Might result in slower bindings, but instead of x:Name="window" and ElementName=window, I tried RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}} and it worked. :) Now to test your suggestion.
Will Pittenger 306 Reputation points

2024-08-08T17:07:43.92+00:00

@Hui Liu-MSFT Didn't work.
Will Pittenger 306 Reputation points

2024-08-08T17:09:28.4+00:00
BTW: The code to move it is as follows and in my Loaded event handler. Too bad there isn't a method I can override for that.

System.Windows.Point ptWhere = ctrlOpenedBy.PointToScreen(new System.Windows.Point(0, 0)); Left = ptWhere.X; Top = ptWhere.Y - ActualHeight;
Will Pittenger 306 Reputation points

2024-08-09T05:12:14.8333333+00:00

When I specified CenterScreen for WindowStartupLocation for my Window, Windows was picking a random monitor. So I added code to WndBase to take that over. But the windows weren't going where I expected. The numbers looked right, but the position was too far to the right and down. It just so happens the distance it's off is similar to the the error I have in my previous post.

The screen dimensions are in pixels. But if Left, Top, Width, and Height are in device units, how do I convert?
Hui Liu-MSFT 48,571 Reputation points Microsoft Vendor

2024-08-09T06:16:26.9466667+00:00

Hi,@Will Pittenger. Could you please share with me a complete reproducible sample for testing?
Will Pittenger 306 Reputation points

2024-08-09T09:06:23.2+00:00

@Hui Liu-MSFT Not currently. I'll see what I can do.
Hui Liu-MSFT 48,571 Reputation points Microsoft Vendor

2024-08-09T09:37:18.44+00:00

Hi,@Will Pittenger. The above two methods are suitable for normal windows. And I see you have found a method that works for your situation
Will Pittenger 306 Reputation points

2024-08-09T09:47:18.8966667+00:00

@Hui Liu-MSFT https://1drv.ms/u/s!An39hJGl5zAVgpgHl5fvX5Bjoc9xJg?e=REcx99 has the project.
Will Pittenger 306 Reputation points

2024-08-09T12:43:28.54+00:00

@Hui Liu-MSFT ??? I don't understand your last message. It isn't working here. Did my project work for you?

Hui Liu-MSFT 48,571 Microsoft Vendor

Hi,@Will Pittenger. The results I got are as follows.

User's image

You could also consider using a UserControl as a child of another window instead of using the window. This problem can be avoided.

If you’re calculating screen dimensions in pixels, but the WPF window's position is using device-independent units (DIPs), you'll need to convert between these units to ensure accurate positioning.


 public partial class GrayWindow : Window

 {

     public GrayWindow()

     {

         InitializeComponent();

         this.Loaded += Window_Loaded;

     }

     private double _leftPosition;

     private double _topPosition;

     public GrayWindow(double left, double top)

     {

         InitializeComponent();

         _leftPosition = left;

         _topPosition = top;

     }

     private void Window_Loaded(object sender, RoutedEventArgs e)

     {

         // Get the DPI scaling factor for the current visual

         var dpi = VisualTreeHelper.GetDpi(this);

         double dpiX = dpi.DpiScaleX;

         double dpiY = dpi.DpiScaleY;

         // Convert from DIP to Physical Pixels

         double leftInPixels = _leftPosition * dpiX;

         double topInPixels = _topPosition * dpiY;

         // Set window position

         Left = leftInPixels;

         Top = topInPixels - this.ActualHeight;

     }

 }

MyTest: Make the custom window always align with the top and left edges of the buttons in the main window, no matter where the main window is located on the screen.

  
  public partial class MainWindow : Window

  {

      GrayWindow grayWindow;

      public MainWindow()

      {

          InitializeComponent();

          LocationChanged += MainWindow_LocationChanged;

      }

      private void MainWindow_LocationChanged(object sender, EventArgs e)

      {

         

          grayWindow?.UpdatePosition();

      }

      private void Window_Loaded(object sender, RoutedEventArgs e)

      {

          ShowGrayWindow();

      }

      private void ShowGrayWindow()

      {

          grayWindow = new GrayWindow(ctrlOpenedBy, this); 

          grayWindow.WindowStartupLocation = WindowStartupLocation.Manual;

          grayWindow.Owner = this;

          grayWindow.Show();

      }

  }

  public partial class GrayWindow : Window
  {
      private Image _controlOpenedBy;

      private Window _ownerWindow;

      public GrayWindow(Image controlOpenedBy, Window ownerWindow)

      {

          InitializeComponent();

          _controlOpenedBy = controlOpenedBy;

          _ownerWindow = ownerWindow;

          _ownerWindow.LocationChanged += OwnerWindow_LocationChanged;

      }

      private void OwnerWindow_LocationChanged(object sender, EventArgs e)

      {

          UpdatePosition();

      }

      internal void UpdatePosition()

      {

          // Get the screen coordinates of the Image control

          System.Windows.Point imagePosition = _controlOpenedBy.PointToScreen(new System.Windows.Point(0, 0));

          // Align GrayWindow with the top and left edges of the Image control

          this.Left = imagePosition.X;

          this.Top = imagePosition.Y - this.ActualHeight; // Adjust as needed

      }

      protected override void OnActivated(EventArgs e)

      {

          base.OnActivated(e);

          UpdatePosition(); // Update position when window is activated

      }

  }

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How to align a WPF window to a child of a second window?

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