SetWindowPlacement won't correct placement for WPF tool windows

Question

I'm p-invoking into SetWindowPlacement in my WPF app to save and restore the window location. This works great but the advertised capacity to make sure a window is never completely hidden doesn't seem to function when the window is a tool window rather than a standard window. You call SetWindowPlacement with negative Left and Right placements and it will happily open it off-screen with no way of getting it back on.

Is there a way I can make SetWindowPlacement correct the placement for these tool windows (for missing monitors and such)?

Failing that, is there a good manual way to do it? For reference, the code:

// 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);
            }
        }
    }
}

Calling SetPlacement with Top: 200, Bottom: 600, Left: -1000, Right: -300.

Answer 1

You can pass your proposed window rectangle to MonitorFromRect() with the MONITOR_DEFAULTTONEAREST flag. This will return an HMONITOR representing the monitor the window most intersects (is on) - or if the window is completely off-screen, the nearest monitor to the proposed coords.

You can then call GetMonitorInfo() to find the monitor's display and workspace rectangles, and bounds-check your proposed window coords to make sure the window is completely on-screen before you show it.