从最大化恢复时的 WPF window 状态卡在奇数状态

Question

我发现 WPF 有一些奇怪的行为。我有一个带有三个按钮的表格。一个按钮应该使 window 全屏，一个按钮应该使它在当前打开的显示器上居中，第三个按钮应该将 window 恢复到它的正常位置。

XAML是

<Window x:Class="TestRestore.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:TestRestore"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525" ResizeMode="CanResizeWithGrip" WindowStartupLocation="CenterScreen">
    <Grid>
        <Button Content="Max" HorizontalAlignment="Left" Margin="10,10,0,0" VerticalAlignment="Top" Width="94" Click="max_click" Name="max_button"/>
        <Button Content="Center" HorizontalAlignment="Left" Margin="10,35,0,0" VerticalAlignment="Top" Width="94" Click="center_click" Name="center_button"/>
        <Button Content="Restore" HorizontalAlignment="Left" Margin="227,143,0,0" VerticalAlignment="Top" Width="75" Click="restore_click" Name="restore_button" IsEnabled="False"/>
    </Grid>
</Window>

代码如下。奇怪的是，当我最大化，然后恢复 window 时，位置被正确恢复，但 window 仍然认为它最大化（最大化按钮看起来像一个恢复按钮，你不能调整大小window 即使 ResizeMode 已设置为 CanResizeWithGrip）。

当最大化的window恢复后，即使window位置没有最大化，它认为它仍然是最大化的，只需拖动标题手动移动window bar 足以使其自行更正为 non-maximized 模式。

此外，如果我最大化然后恢复 window 然后再次最大化它而不移动它，最大化的 window 位置不正确（不在左上角）。

谜团加深了。如果我最大化然后恢复 window，然后按 alt，然后按下（获得 window 菜单）和 select 'Move' 然后移动 window在键盘周围，即使 window 正在移动，它仍然卡在 'bogus not-mazimized mode' 中，所以似乎唯一的方法就是用鼠标移动它。

using System;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;

namespace TestRestore
{
    public partial class MainWindow : Window
    {
        WindowStyle old_window_style;
        WindowState old_window_state;
        double old_left;
        double old_top;
        double old_width;
        double old_height;

        public MainWindow()
        {
            InitializeComponent();
        }

        // remember position, style and state
        private void SaveWindowPos()
        {
            old_window_style = WindowStyle;
            old_window_state = WindowState;
            old_left = Left;
            old_top = Top;
            old_width = Width;
            old_height = Height;
            max_button.IsEnabled = false;
            center_button.IsEnabled = false;
            restore_button.IsEnabled = true;
        }

        // put position, style and state back
        private void RestoreWindowPos()
        {
            WindowStyle = old_window_style;
            WindowState = old_window_state;
            ResizeMode = ResizeMode.CanResizeWithGrip;
            Left = old_left;
            Top = old_top;
            Width = old_width;
            Height = old_height;
            max_button.IsEnabled = true;
            center_button.IsEnabled = true;
            restore_button.IsEnabled = false;
        }

        // make it centered or fullscreen
        private void SetActivePos(bool full_screen)
        {
            SaveWindowPos();
            Hide();
            if (full_screen)
            {
                ResizeMode = ResizeMode.NoResize;
                WindowStyle = WindowStyle.None;
                WindowState = WindowState.Maximized;
            }
            else
            {
                Size s = new Size(800, 600);
                Point p = CenterRectInMonitor(this, s);
                Left = p.X;
                Top = p.Y;
                Width = s.Width;
                Height = s.Height;
                ResizeMode = ResizeMode.NoResize;
                WindowState = WindowState.Normal;
            }
            Show();
        }

        private void restore_click(object sender, RoutedEventArgs e)
        {
            Hide();
            RestoreWindowPos();
            Show();
        }

        private void max_click(object sender, RoutedEventArgs e)
        {
            SetActivePos(true);
        }

        private void center_click(object sender, RoutedEventArgs e)
        {
            SetActivePos(false);
        }

        // interop

        public const Int32 MONITOR_DEFAULTTOPRIMARY = 0x00000001;
        public const Int32 MONITOR_DEFAULTTONEAREST = 0x00000002;

        [DllImport("user32.dll")]
        public static extern IntPtr MonitorFromWindow(IntPtr handle, Int32 flags);

        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern bool GetMonitorInfo(IntPtr hMonitor, ref MonitorInfoEx lpmi);

        // size of a device name string
        private const int CCHDEVICENAME = 32;

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
        public struct MonitorInfoEx
        {
            public int Size;
            public RectStruct Monitor;
            public RectStruct WorkArea;
            public uint Flags;

            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = CCHDEVICENAME)]
            public string DeviceName;

            public void Init()
            {
                this.Size = 40 + 2 * CCHDEVICENAME;
                this.DeviceName = string.Empty;
            }
        }

        [StructLayout(LayoutKind.Sequential)]
        public struct RectStruct
        {
            public int Left;
            public int Top;
            public int Right;
            public int Bottom;

            public int Width
            {
                get
                {
                    return Right - Left;
                }
            }

            public int Height
            {
                get
                {
                    return Bottom - Top;
                }
            }
        }

        public static MonitorInfoEx GetMonitorFromWindow(Window w)
        {
            var hwnd = new WindowInteropHelper(w).EnsureHandle();
            var monitor = MonitorFromWindow(hwnd, MONITOR_DEFAULTTONEAREST);
            MonitorInfoEx monitor_info = new MonitorInfoEx();
            monitor_info.Init();
            GetMonitorInfo(monitor, ref monitor_info);
            return monitor_info;
        }

        // work out how a rect of 'Size size' should be centered on the monitor containing 'Window w'
        public static Point CenterRectInMonitor(Window w, Size size)
        {
            var source = PresentationSource.FromVisual(w);
            double x_scale = source.CompositionTarget.TransformToDevice.M11;
            double y_scale = source.CompositionTarget.TransformToDevice.M22;
            var width = size.Width * x_scale;
            var height = size.Height * y_scale;
            var monitor_info = GetMonitorFromWindow(w);
            Size s = new Size(monitor_info.Monitor.Width, monitor_info.Monitor.Height);
            Point p = new Point(monitor_info.Monitor.Left, monitor_info.Monitor.Top);
            Point c = new Point(p.X + s.Width / 2, p.Y + s.Height / 2);
            return new Point((c.X - width / 2) / x_scale, (c.Y - height / 2) / y_scale);
        }
    }
}

Answer 1

我没有完整的答案给你。但是，您会发现一旦删除 Hide() 和 Show() 调用，您的代码就会开始工作得更好。

    private void restore_click(object sender, RoutedEventArgs e)
    {
//            Hide();
        RestoreWindowPos();
//            Show();
    }

我确定你放入这个是为了减少闪烁，但我认为正在发生的是 Hide() 和 Show() 调用正在翻转 window 中的 WS_VISIBLE 位底层 OS window 的样式词与包含 WS_MAXIMIZE 和 WS_BORDER 以及您正在操纵的其他一些东西的词相同。参见 https://msdn.microsoft.com/en-us/library/windows/desktop/ms632600(v=vs.85).aspx

需要更多的研究才能弄清楚到底发生了什么，但我认为根本问题是 "leaky abstraction"。您的代码设置顶部、左侧、样式和状态，就好像它们是独立的非耦合变量一样。但他们不是！要设置左侧，必须调用 OS SetWindowPos() 函数，它不需要左上角坐标、window 大小、Z 顺序以及可见性标志以及 windows 是否是最大化！参见 https://msdn.microsoft.com/en-us/library/windows/desktop/ms633545(v=vs.85).aspx。因此，每次您设置其中一个 "independent" 变量时，您都会调用 SetWindowPos()。这个 API 调用让人回想起过去糟糕的日子，当时 CPU 周期非常宝贵，您需要在每个 API 调用中包含尽可能多的功能。

具有讽刺意味的是，这会使您的代码变得非常低效。我认为解决这个问题的方法是绕过 System.Windows.Window 的泄漏抽象并直接从 user32.dll 调用 SetWindowPos 和可能的其他 API 函数。那么事情就会变得更加可预测。

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