How to fix the WPF form resize - controls lagging behind and black background?

Question

I have a very simple WPF window - the only thing in it is a right-aligned button. When I resize the window by dragging the left boundary, the button jumps around - a lot. Try it yourself, drag the left boundary back and forth.

Additionally, a black background becomes exposed temporarily during resizes.

In this question, I asked a similar question about Windows Forms. The only answer I got suggested that this is fixed in WPF, however, amazingly, not only is it not fixed, but WPF also adds a second visual bug - the temporary black background.

Here's what the control lag looks like; this occurs when I resize the window by its top border (recorded with a camera because screen-cap made it less obvious by making everything slow):

                                                 

Example of the black border: this was captured while resizing the window; it's only like this for a split second but it's very noticeable:

                                     

Am I doing something wrong? How can I have my controls stay visually in one place during resizes? How can I avoid the black border?

Note: the button ends up in the correct place eventually - it only jumps around briefly during the resize.

Answer 1

This is complete working code based on Wieser Software Ltd's 2nd solution.

public partial class MainView : Window
{
    public MainView()
    {
        InitializeComponent();

        //ensure win32 handle is created
        var handle = new WindowInteropHelper(this).EnsureHandle();

        //set window background
        var result = SetClassLong(handle, GCL_HBRBACKGROUND, GetSysColorBrush(COLOR_WINDOW));
    }

    public static IntPtr SetClassLong(IntPtr hWnd, int nIndex, IntPtr dwNewLong)
    {
        //check for x64
        if (IntPtr.Size > 4)
            return SetClassLongPtr64(hWnd, nIndex, dwNewLong);
        else
            return new IntPtr(SetClassLongPtr32(hWnd, nIndex, unchecked((uint)dwNewLong.ToInt32())));
    }

    private const int GCL_HBRBACKGROUND = -10;
    private const int COLOR_WINDOW = 5;

    [DllImport("user32.dll", EntryPoint = "SetClassLong")]
    public static extern uint SetClassLongPtr32(IntPtr hWnd, int nIndex, uint dwNewLong);

    [DllImport("user32.dll", EntryPoint = "SetClassLongPtr")]
    public static extern IntPtr SetClassLongPtr64(IntPtr hWnd, int nIndex, IntPtr dwNewLong);

    [DllImport("user32.dll")]
    static extern IntPtr GetSysColorBrush(int nIndex);
}