Saving window size and location in WPF and WinForms

RandomEngy

8 Mar 2010 7:18 PM

Comments 11

A common user interface tweak is to save the size and location of a window and restore that state when the program starts up again. That way, the users don’t need to re-do their work of resizing and moving the windows to where they want them. However I’ve found that there isn’t really a convenient way to do with in C#. Many solutions focus on recording the window width, height, x and y coordinates and current state (maximized, restored, etc), then applying all those values again on startup. But then you have to deal with edge cases: What if the user has changed resolutions since your program last ran? What if it was present on a monitor that’s now disconnected?

Fortunately, there are a couple of native Windows functions that can do all this work for us: SetWindowPlacement and GetWindowPlacement. MSDN has a sample demonstrating how to PInvoke to these functions in a WPF project, but it’s got a few issues with it. For one, it’s trying to store the placement as a custom type in settings, which can cause strange errors every time you open your Settings file. Here’s my take on it:

using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using System.Xml;
using System.Xml.Serialization;

namespace WindowPlacementExample
{
    // RECT structure required by WINDOWPLACEMENT structure
    [Serializable]
    [StructLayout(LayoutKind.Sequential)]
    public struct RECT
    {
        public int Left;
        public int Top;
        public int Right;
        public int Bottom;

        public RECT(int left, int top, int right, int bottom)
        {
            this.Left = left;
            this.Top = top;
            this.Right = right;
            this.Bottom = bottom;
        }
    }

    // POINT structure required by WINDOWPLACEMENT structure
    [Serializable]
    [StructLayout(LayoutKind.Sequential)]
    public struct POINT
    {
        public int X;
        public int Y;

        public POINT(int x, int y)
        {
            this.X = x;
            this.Y = y;
        }
    }

    // WINDOWPLACEMENT stores the position, size, and state of a window
    [Serializable]
    [StructLayout(LayoutKind.Sequential)]
    public struct WINDOWPLACEMENT
    {
        public int length;
        public int flags;
        public int showCmd;
        public POINT minPosition;
        public POINT maxPosition;
        public RECT normalPosition;
    }

    public static class WindowPlacement
    {
        private static Encoding encoding = new UTF8Encoding();
        private static XmlSerializer serializer = new XmlSerializer(typeof(WINDOWPLACEMENT));

        [DllImport("user32.dll")]
        private static extern bool SetWindowPlacement(IntPtr hWnd, [In] ref WINDOWPLACEMENT lpwndpl);

        [DllImport("user32.dll")]
        private static extern bool GetWindowPlacement(IntPtr hWnd, out WINDOWPLACEMENT lpwndpl);

        private const int SW_SHOWNORMAL = 1;
        private const int SW_SHOWMINIMIZED = 2;

        public static void SetPlacement(IntPtr windowHandle, string placementXml)
        {
            if (string.IsNullOrEmpty(placementXml))
            {
                return;
            }

            WINDOWPLACEMENT placement;
            byte[] xmlBytes = encoding.GetBytes(placementXml);

            try
            {
                using (MemoryStream memoryStream = new MemoryStream(xmlBytes))
                {
                    placement = (WINDOWPLACEMENT)serializer.Deserialize(memoryStream);
                }

                placement.length = Marshal.SizeOf(typeof(WINDOWPLACEMENT));
                placement.flags = 0;
                placement.showCmd = (placement.showCmd == SW_SHOWMINIMIZED ? SW_SHOWNORMAL : placement.showCmd);
                SetWindowPlacement(windowHandle, ref placement);
            }
            catch (InvalidOperationException)
            {
                // Parsing placement XML failed. Fail silently.
            }
        }

        public static string GetPlacement(IntPtr windowHandle)
        {
            WINDOWPLACEMENT placement = new WINDOWPLACEMENT();
            GetWindowPlacement(windowHandle, out placement);

            using (MemoryStream memoryStream = new MemoryStream())
            {
                using (XmlTextWriter xmlTextWriter = new XmlTextWriter(memoryStream, Encoding.UTF8))
                {
                    serializer.Serialize(xmlTextWriter, placement);
                    byte[] xmlBytes = memoryStream.ToArray();
                    return encoding.GetString(xmlBytes);
                }
            }
        }
    }
}

To get the placement of an existing window, you give it the native handle for the window, and get back a string of XML that represents the placement for the window. You save this string somewhere, then when the program starts back up again, apply it with SetPlacement. The above code works for both WinForms and WPF. And in both cases you can open your Properties/Settings.settings file and add a new setting to store the string:

This will store the window state locally, per-user. Of course you could also store the string wherever you wanted to.

What I like about this approach is that the WindowPlacement class does the XML serialization for you and gives you a nice, tidy string containing all the placement data.

But where in the program code should we hook in to save and re-apply the window placements? The answer is a bit different between WinForms and WPF.

WPF:

You might benefit by throwing a couple of extension methods on the WindowPlacement class to make things a bit easier:

public static void SetPlacement(this Window window, string placementXml)
{
    WindowPlacement.SetPlacement(new WindowInteropHelper(window).Handle, placementXml);
}

public static string GetPlacement(this Window window)
{
    return WindowPlacement.GetPlacement(new WindowInteropHelper(window).Handle);
}

To save the window placement, just handle the Closing event on the Window:

private void Window_Closing(object sender, CancelEventArgs e)
{
    Settings.Default.MainWindowPlacement = this.GetPlacement();
    Settings.Default.Save();
}

To restore, you’ll need to hook in on SourceInitialized:

protected override void OnSourceInitialized(EventArgs e)
{
    base.OnSourceInitialized(e);
    this.SetPlacement(Settings.Default.MainWindowPlacement);
}

WinForms:

This one is a bit more straightforward. Save on the FormClosing event and restore the window state in the Load event handler. The Form’s native handle is accessible from its Handle property.

Now we have a robust and relatively painless way of persisting window sizes and positions, and we only need to keep track of one string per window.

Comments

Tony

26 May 2010 3:36 AM

Please can someone for once write this for VB.net and wpf not all of us code in C
Jeff

11 Aug 2010 7:46 AM

Get an error on this line:

placement = (WINDOWPLACEMENT)serializer.Deserialize(memoryStream);

Data at the root level is invalid. Line 1 Position 1

I'm saving the string to a database field, then reading it in. Any ideas?
Jeff

11 Aug 2010 9:20 AM

I ended up NOT using UTF-8 encoding (human readability wasn't a factor for me). UTF-8 has a BOM (Byte Order Marker) that wasn't being encoded/decoded correctly when I saved my string out to the db. I ended up using Convert.ToBase64String and Convert.FromBase64String.

Otherwise it works great! Thanks!
Dave

21 Dec 2010 12:25 PM

Thanks for the Article - It made the task easy.

I was also saving to a DB (SQL 2K - uggh) and I just changed the encoding to ASCII since I still wanted to be able to read the saved xml.

Changed lines:

private static Encoding encoding = new ASCIIEncoding();

using (XmlTextWriter xmlTextWriter = new XmlTextWriter(memoryStream, Encoding.ASCII))
JustMe

22 Jan 2011 1:46 PM

Looks like REALLY useful code, but it's all cut off on the right side...
RandomEngy

25 Jan 2011 10:01 AM

Yeah they changed the blog formatting on me. I just switched up the layout so you should be able to see everything now. (though you can always copy/paste and get everything anyway)
Gary

12 Apr 2011 9:00 PM

Very nice solution for this. Thanks.
Lordman

3 Oct 2011 11:21 PM

Where can I find: Properties/Settings.settings file?
Lordman

4 Oct 2011 12:44 AM

BindingFailure was detect in :(

private static XmlSerializer serializer = new XmlSerializer(typeof(WINDOWPLACEMENT));
RandomEngy

1 Nov 2011 10:35 AM

@Lordman: It's usually added by default in GUI projects. If you don't have it, you can Add New Item -> Visual C# -> General -> Settings File.
MPAULUS

20 Jul 2012 5:53 AM

Here is my translation to VB.NET:

Namespace Extensions

Public Module WindowExtensions

#Region "Properties"

Private Property Encoding As System.Text.Encoding = New System.Text.UTF8Encoding()

Private Property Serializer As New System.Xml.Serialization.XmlSerializer(GetType(NativeMethods.WINDOWPLACEMENT))

#End Region

#Region "Extension Methods"

<System.Runtime.CompilerServices.Extension> _

Public Sub SetPlacement(window As Window, placementXml As String)

If Not String.IsNullOrEmpty(placementXml) Then

SetPlacement(New System.Windows.Interop.WindowInteropHelper(window).Handle, placementXml)

End If

End Sub

<System.Runtime.CompilerServices.Extension> _

Public Sub SetPlacement(form As System.Windows.Forms.Form, placementXml As String)

If Not String.IsNullOrEmpty(placementXml) Then

SetPlacement(form.Handle, placementXml)

End If

End Sub

<System.Runtime.CompilerServices.Extension> _

Public Function GetPlacement(window As Window) As String

Return GetPlacement(New System.Windows.Interop.WindowInteropHelper(window).Handle)

End Function

<System.Runtime.CompilerServices.Extension> _

Public Function GetPlacement(form As System.Windows.Forms.Form) As String

Return GetPlacement(form.Handle)

End Function

#End Region

#Region "Supporting Methods"

Private Sub SetPlacement(windowHandle As IntPtr, placementXml As String)

If String.IsNullOrEmpty(placementXml) Then

Return

End If

Dim placement As NativeMethods.WINDOWPLACEMENT

Dim xmlBytes As Byte() = Encoding.GetBytes(placementXml)

Try

Using memoryStream As New System.IO.MemoryStream(xmlBytes)

placement = DirectCast(Serializer.Deserialize(memoryStream), NativeMethods.WINDOWPLACEMENT)

End Using

placement.length = System.Runtime.InteropServices.Marshal.SizeOf(GetType(NativeMethods.WINDOWPLACEMENT))

placement.flags = 0

placement.showCmd = (If(placement.showCmd = NativeMethods.ShowWindowCommands.ShowMinimized, NativeMethods.ShowWindowCommands.Normal, placement.showCmd))

NativeMethods.SetWindowPlacement(windowHandle, placement)

' Parsing placement XML failed. Fail silently.

Catch generatedExceptionName As InvalidOperationException

End Try

End Sub

Private Function GetPlacement(windowHandle As IntPtr) As String

Dim placement As New NativeMethods.WINDOWPLACEMENT()

NativeMethods.GetWindowPlacement(windowHandle, placement)

Using memoryStream As New System.IO.MemoryStream

Using xmlTextWriter As New System.Xml.XmlTextWriter(memoryStream, System.Text.Encoding.UTF8)

Serializer.Serialize(xmlTextWriter, placement)

Dim xmlBytes As Byte() = memoryStream.ToArray()

Return Encoding.GetString(xmlBytes)

End Using

End Using

End Function

#End Region

End Module

End Namespace

Namespace Extensions

Public Class NativeMethods

<System.Runtime.InteropServices.DllImport("user32.dll")> _

Public Shared Function SetWindowPlacement(ByVal hWnd As IntPtr, ByRef lpwndpl As WINDOWPLACEMENT) As Boolean

End Function

<System.Runtime.InteropServices.DllImport("user32.dll")> _

Public Shared Function GetWindowPlacement(ByVal hWnd As IntPtr, ByRef lpwndpl As WINDOWPLACEMENT) As Boolean

End Function

' RECT structure required by WINDOWPLACEMENT structure

<Serializable>

<System.Runtime.InteropServices.StructLayout(System.Runtime.InteropServices.LayoutKind.Sequential)>

Public Structure RECT

Public Left As Integer

Public Top As Integer

Public Right As Integer

Public Bottom As Integer

Public Sub New(left As Integer, top As Integer, right As Integer, bottom As Integer)

Me.Left = left

Me.Top = top

Me.Right = right

Me.Bottom = bottom

End Sub

End Structure

' POINT structure required by WINDOWPLACEMENT structure

<Serializable>

<System.Runtime.InteropServices.StructLayout(System.Runtime.InteropServices.LayoutKind.Sequential)>

Public Structure POINT

Public X As Integer

Public Y As Integer

Public Sub New(x As Integer, y As Integer)

Me.X = x

Me.Y = y

End Sub

End Structure

' WINDOWPLACEMENT stores the position, size, and state of a window

<Serializable>

<System.Runtime.InteropServices.StructLayout(System.Runtime.InteropServices.LayoutKind.Sequential)>

Public Structure WINDOWPLACEMENT

Public length As Integer

Public flags As Integer

Public showCmd As ShowWindowCommands

Public minPosition As POINT

Public maxPosition As POINT

Public normalPosition As RECT

End Structure

Public Enum ShowWindowCommands As Integer

Hide = 0

Normal = 1

ShowMinimized = 2

Maximize = 3

ShowMaximized = 3

ShowNoActivate = 4

Show = 5

Minimize = 6

ShowMinNoActive = 7

ShowNA = 8

Restore = 9

ShowDefault = 10

ForceMinimize = 11

End Enum

End Class

End Namespace

David Rickard's Tech Blog

Saving window size and location in WPF and WinForms

Saving window size and location in WPF and WinForms