6502bench/CommonWPF/WindowPlacement.cs

/*
 * This comes from a blog entry, posted by RandomEngy on March 8 2010:
 * https://blogs.msdn.microsoft.com/davidrickard/2010/03/08/saving-window-size-and-location-in-wpf-and-winforms/
 * (see https://stackoverflow.com/a/2406604/294248 for discussion)
 * 
 * Saving and restoring a window's size and position can be tricky when there are multiple
 * displays involved.  This uses the Win32 system functions to do the job properly and
 * consistently.  (In theory.)
 * 
 * The code works for WinForms (save on FormClosing, restore on Load, using the native handle
 * from the Handle property) and WPF (use the Window extension methods provided below, in
 * Closing and SourceInitialized).  Besides convenience, it has the added benefit of being able
 * to capture the non-maximized values for a maximized window.
 */

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

namespace CommonWPF {
    // 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);
                }
            }
        }

        //
        // Extension methods for WPF.
        //

        // Call from Closing event.  Returns XML string with placement info.
        public static string GetPlacement(this Window window) {
            return GetPlacement(new WindowInteropHelper(window).Handle);
        }
        // Call from SourceInitialized event, passing in string from GetPlacement().
        public static void SetPlacement(this Window window, string placementXml) {
            SetPlacement(new WindowInteropHelper(window).Handle, placementXml);
        }
    }
}