WPF使用AppBar实现窗口停靠，适配缩放、全屏响应和多窗口并列（附封装好即开即用的附加属性）

在吕毅大佬的文章中已经详细介绍了什么是AppBar: WPF 使用 AppBar 将窗口停靠在桌面上，让其他程序不占用此窗口的空间（附我封装的附加属性） - walterlv

即让窗口固定在屏幕某一边，并且保证其他窗口最大化后不会覆盖AppBar占据的区域（类似于Windows任务栏）。

但是在我的环境中测试时，上面的代码出现了一些问题，例如非100%缩放显示时的坐标计算异常、多窗口同时停靠时布局错乱等。所以我重写了AppBar在WPF上的实现，效果如图：

一、AppBar的主要申请流程

主要流程如图：

（图注：ABN_POSCHANGED消息在任何需要调整位置之时都会触发，括号只是举个例子）

核心代码其实在于如何计算停靠窗口的位置，要点是处理好一下几个方面：

1. 修改停靠位置时用原窗口的大小计算，被动告知需要调整位置时用即时大小计算

2. 像素单位与WPF单位之间的转换

3. 小心Windows的位置建议，并排停靠时会得到负值高宽，需要手动适配对齐方式

4. 有新的AppBar加入时，窗口会被系统强制移动到工作区(WorkArea)，这点我还没能找到解决方案，只能把移动窗口的命令通过Dispatcher延迟操作

二、如何使用

1.下载我封装好的库：AppBarTest/AppBarCreator.cs at master · TwilightLemon/AppBarTest (github.com)

2. 在xaml中直接设置：

<Window ...>

<local:AppBarCreator.AppBar>
    <local:AppBar x:Name="appBar" Location="Top" OnFullScreenStateChanged="AppBar_OnFullScreenStateChanged"/>
</local:AppBarCreator.AppBar>

...
</Window>

或者在后台创建：

private readonly AppBar appBar=new AppBar();

...Window_Loaded...
appBar.Location = AppBarLocation.Top;
appBar.OnFullScreenStateChanged += AppBar_OnFullScreenStateChanged;
AppBarCreator.SetAppBar(this, appBar);

3. 另外你可能注意到了，这里有一个OnFullScreenStateChanged事件：该事件由AppBarMsg注册，在有窗口进入或退出全屏时触发，参数bool为true指示进入全屏。

你需要手动在事件中设置全屏模式下的行为，例如在全屏时隐藏AppBar

    private void AppBar_OnFullScreenStateChanged(object sender, bool e)
    {
        Debug.WriteLine("Full Screen State: "+e);
        Visibility = e ? Visibility.Collapsed : Visibility.Visible;
    }

我在官方的Flag上加了一个RegisterOnly，即只注册AppBarMsg而不真的停靠窗口，可以此用来作全屏模式监听。

4. 如果你需要在每个虚拟桌面都显示AppBar(像任务栏那样)，可以尝试为窗口使用SetWindowLong添加WS_EX_TOOLWINDOW标签（自行查找）

以下贴出完整的代码：

  1 using System.ComponentModel;
  2 using System.Diagnostics;
  3 using System.Runtime.InteropServices;
  4 using System.Windows;
  5 using System.Windows.Interop;
  6 using System.Windows.Threading;
  7 
  8 namespace AppBarTest;
  9 public static class AppBarCreator
 10 {
 11     public static readonly DependencyProperty AppBarProperty =
 12         DependencyProperty.RegisterAttached(
 13             "AppBar",
 14             typeof(AppBar),
 15             typeof(AppBarCreator),
 16             new PropertyMetadata(null, OnAppBarChanged));
 17     private static void OnAppBarChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
 18     {
 19         if (d is Window window && e.NewValue is AppBar appBar)
 20         {
 21             appBar.AttachedWindow = window;
 22         }
 23     }
 24     public static void SetAppBar(Window element, AppBar value)
 25     {
 26         if (value == null) return;
 27         element.SetValue(AppBarProperty, value);
 28     }
 29 
 30     public static AppBar GetAppBar(Window element)
 31     {
 32         return (AppBar)element.GetValue(AppBarProperty);
 33     }
 34 }
 35 
 36 public class AppBar : DependencyObject
 37 {
 38     /// <summary>
 39     /// 附加到的窗口
 40     /// </summary>
 41     public Window AttachedWindow
 42     {
 43         get => _window;
 44         set
 45         {
 46             if (value == null) return;
 47             _window = value;
 48             _window.Closing += _window_Closing;
 49             _window.LocationChanged += _window_LocationChanged;
 50             //获取窗口句柄hWnd
 51             var handle = new WindowInteropHelper(value).Handle;
 52             if (handle == IntPtr.Zero)
 53             {
 54                 //Win32窗口未创建
 55                 _window.SourceInitialized += _window_SourceInitialized;
 56             }
 57             else
 58             {
 59                 _hWnd = handle;
 60                 CheckPending();
 61             }
 62         }
 63     }
 64 
 65     private void _window_LocationChanged(object? sender, EventArgs e)
 66     {
 67         Debug.WriteLine(_window.Title+ " LocationChanged: Top: "+_window.Top+"  Left: "+_window.Left);
 68     }
 69 
 70     private void _window_Closing(object? sender, CancelEventArgs e)
 71     {
 72         _window.Closing -= _window_Closing;
 73         if (Location != AppBarLocation.None)
 74             DisableAppBar();
 75     }
 76 
 77     /// <summary>
 78     /// 检查是否需要应用之前的Location更改
 79     /// </summary>
 80     private void CheckPending()
 81     {
 82         //创建AppBar时提前触发的LocationChanged
 83         if (_locationChangePending)
 84         {
 85             _locationChangePending = false;
 86             LoadAppBar(Location);
 87         }
 88     }
 89     /// <summary>
 90     /// 载入AppBar
 91     /// </summary>
 92     /// <param name="e"></param>
 93     private void LoadAppBar(AppBarLocation e,AppBarLocation? previous=null)
 94     {
 95         
 96         if (e != AppBarLocation.None)
 97         {
 98             if (e == AppBarLocation.RegisterOnly)
 99             {
100                 //仅注册AppBarMsg
101                 //如果之前注册过有效的AppBar则先注销，以还原位置
102                 if (previous.HasValue && previous.Value != AppBarLocation.RegisterOnly)
103                 {
104                     if (previous.Value != AppBarLocation.None)
105                     {
106                         //由生效的AppBar转为RegisterOnly，还原为普通窗口再注册空AppBar
107                         DisableAppBar();
108                     }
109                     RegisterAppBarMsg();
110                 }
111                 else
112                 {
113                     //之前未注册过AppBar，直接注册
114                     RegisterAppBarMsg();
115                 }
116             }
117             else
118             {
119                 if (previous.HasValue && previous.Value != AppBarLocation.None)
120                 {
121                     //之前为RegisterOnly才备份窗口信息
122                     if(previous.Value == AppBarLocation.RegisterOnly)
123                     {
124                         BackupWindowInfo();
125                     }
126                     SetAppBarPosition(_originalSize);
127                     ForceWindowStyles();
128                 }
129                 else
130                     EnableAppBar();
131             }
132         }
133         else
134         {
135             DisableAppBar();
136         }
137     }
138     private void _window_SourceInitialized(object? sender, EventArgs e)
139     {
140         _window.SourceInitialized -= _window_SourceInitialized;
141         _hWnd = new WindowInteropHelper(_window).Handle;
142         CheckPending();
143     }
144 
145     /// <summary>
146     /// 当有窗口进入或退出全屏时触发 bool参数为true时表示全屏状态
147     /// </summary>
148     public event EventHandler<bool>? OnFullScreenStateChanged;
149     /// <summary>
150     /// 期望将AppBar停靠到的位置
151     /// </summary>
152     public AppBarLocation Location
153     {
154         get { return (AppBarLocation)GetValue(LocationProperty); }
155         set { SetValue(LocationProperty, value); }
156     }
157 
158     public static readonly DependencyProperty LocationProperty =
159         DependencyProperty.Register(
160             "Location",
161             typeof(AppBarLocation), typeof(AppBar),
162             new PropertyMetadata(AppBarLocation.None, OnLocationChanged));
163 
164     private bool _locationChangePending = false;
165     private static void OnLocationChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
166     {
167         if (DesignerProperties.GetIsInDesignMode(d))
168             return;
169         if (d is not AppBar appBar) return;
170         if (appBar.AttachedWindow == null)
171         {
172             appBar._locationChangePending = true;
173             return;
174         }
175         appBar.LoadAppBar((AppBarLocation)e.NewValue,(AppBarLocation)e.OldValue);
176     }
177 
178     private int _callbackId = 0;
179     private bool _isRegistered = false;
180     private Window _window = null;
181     private IntPtr _hWnd;
182     private WindowStyle _originalStyle;
183     private Point _originalPosition;
184     private Size _originalSize = Size.Empty;
185     private ResizeMode _originalResizeMode;
186     private bool _originalTopmost;
187     public Rect? DockedSize { get; set; } = null;
188     private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam,
189                                     IntPtr lParam, ref bool handled)
190     {
191         if (msg == _callbackId)
192         {
193             Debug.WriteLine(_window.Title + " AppBarMsg("+_callbackId+"): " + wParam.ToInt32() + " LParam: " + lParam.ToInt32());
194             switch (wParam.ToInt32())
195             {
196                 case (int)Interop.AppBarNotify.ABN_POSCHANGED:
197                     Debug.WriteLine("AppBarNotify.ABN_POSCHANGED ! "+_window.Title);
198                     if (Location != AppBarLocation.RegisterOnly)
199                         SetAppBarPosition(Size.Empty);
200                     handled = true;
201                     break;
202                 case (int)Interop.AppBarNotify.ABN_FULLSCREENAPP:
203                     OnFullScreenStateChanged?.Invoke(this, lParam.ToInt32() == 1);
204                     handled = true;
205                     break;
206             }
207         }
208         return IntPtr.Zero;
209     }
210 
211     public void BackupWindowInfo()
212     {
213         _callbackId = 0;
214         DockedSize = null;
215         _originalStyle = _window.WindowStyle;
216         _originalSize = new Size(_window.ActualWidth, _window.ActualHeight);
217         _originalPosition = new Point(_window.Left, _window.Top);
218         _originalResizeMode = _window.ResizeMode;
219         _originalTopmost = _window.Topmost;
220     }
221     public void RestoreWindowInfo()
222     {
223         if (_originalSize != Size.Empty)
224         {
225             _window.WindowStyle = _originalStyle;
226             _window.ResizeMode = _originalResizeMode;
227             _window.Topmost = _originalTopmost;
228             _window.Left = _originalPosition.X;
229             _window.Top = _originalPosition.Y;
230             _window.Width = _originalSize.Width;
231             _window.Height = _originalSize.Height;
232         }
233     }
234     public void ForceWindowStyles()
235     {
236         _window.WindowStyle = WindowStyle.None;
237         _window.ResizeMode = ResizeMode.NoResize;
238         _window.Topmost = true;
239     }
240 
241     public void RegisterAppBarMsg()
242     {
243         var data = new Interop.APPBARDATA();
244         data.cbSize = Marshal.SizeOf(data);
245         data.hWnd = _hWnd;
246 
247         _isRegistered = true;
248         _callbackId = Interop.RegisterWindowMessage(Guid.NewGuid().ToString());
249         data.uCallbackMessage = _callbackId;
250         var success = Interop.SHAppBarMessage((int)Interop.AppBarMsg.ABM_NEW, ref data);
251         var source = HwndSource.FromHwnd(_hWnd);
252         Debug.WriteLineIf(source == null, "HwndSource is null!");
253         source?.AddHook(WndProc);
254         Debug.WriteLine(_window.Title+" RegisterAppBarMsg: " + _callbackId);
255     }
256     public void EnableAppBar()
257     {
258         if (!_isRegistered)
259         {
260             //备份窗口信息并设置窗口样式
261             BackupWindowInfo();
262             //注册成为AppBar窗口
263             RegisterAppBarMsg();
264             ForceWindowStyles();
265         }
266         //成为AppBar窗口之后(或已经是)只需要注册并移动窗口位置即可
267         SetAppBarPosition(_originalSize);
268     }
269     public void SetAppBarPosition(Size WindowSize)
270     {
271         var data = new Interop.APPBARDATA();
272         data.cbSize = Marshal.SizeOf(data);
273         data.hWnd = _hWnd;
274         data.uEdge = (int)Location;
275         data.uCallbackMessage = _callbackId;
276         Debug.WriteLine("\r\nWindow: "+_window.Title);
277 
278         //获取WPF单位与像素的转换矩阵
279         var compositionTarget = PresentationSource.FromVisual(_window)?.CompositionTarget;
280         if (compositionTarget == null)
281             throw new Exception("居然获取不到CompositionTarget?!");
282         var toPixel = compositionTarget.TransformToDevice;
283         var toWpfUnit = compositionTarget.TransformFromDevice;
284 
285         //窗口在屏幕的实际大小
286         if(WindowSize== Size.Empty)
287             WindowSize = new Size(_window.ActualWidth, _window.ActualHeight);
288         var actualSize = toPixel.Transform(new Vector(WindowSize.Width, WindowSize.Height));
289         //屏幕的真实像素
290         var workArea = toPixel.Transform(new Vector(SystemParameters.PrimaryScreenWidth, SystemParameters.PrimaryScreenHeight));
291         Debug.WriteLine("WorkArea Width: {0}, Height: {1}", workArea.X, workArea.Y);
292 
293         if (Location is AppBarLocation.Left or AppBarLocation.Right)
294         {
295             data.rc.top = 0;
296             data.rc.bottom = (int)workArea.Y;
297             if (Location == AppBarLocation.Left)
298             {
299                 data.rc.left = 0;
300                 data.rc.right =  (int)Math.Round(actualSize.X);
301             }
302             else
303             {
304                 data.rc.right = (int)workArea.X;
305                 data.rc.left = (int)workArea.X - (int)Math.Round(actualSize.X);
306             }
307         }
308         else
309         {
310             data.rc.left = 0;
311             data.rc.right = (int)workArea.X;
312             if (Location == AppBarLocation.Top)
313             {
314                 data.rc.top = 0;
315                 data.rc.bottom = (int)Math.Round(actualSize.Y);
316             }
317             else
318             {
319                 data.rc.bottom = (int)workArea.Y;
320                 data.rc.top = (int)workArea.Y - (int)Math.Round(actualSize.Y);
321             }
322         }
323         //以上生成的是四周都没有其他AppBar时的理想位置
324         //系统将自动调整位置以适应其他AppBar
325         Debug.WriteLine("Before QueryPos: Left: {0}, Top: {1}, Right: {2}, Bottom: {3}", data.rc.left, data.rc.top, data.rc.right, data.rc.bottom);
326         Interop.SHAppBarMessage((int)Interop.AppBarMsg.ABM_QUERYPOS, ref data);
327         Debug.WriteLine("After QueryPos: Left: {0}, Top: {1}, Right: {2}, Bottom: {3}", data.rc.left, data.rc.top, data.rc.right, data.rc.bottom);
328         //自定义对齐方式，确保Height和Width不会小于0
329         if (data.rc.bottom - data.rc.top < 0)
330         {
331             if (Location == AppBarLocation.Top)
332                 data.rc.bottom = data.rc.top + (int)Math.Round(actualSize.Y);//上对齐
333             else if (Location == AppBarLocation.Bottom)
334                 data.rc.top = data.rc.bottom - (int)Math.Round(actualSize.Y);//下对齐
335         }
336         if(data.rc.right - data.rc.left < 0)
337         {
338             if (Location == AppBarLocation.Left)
339                 data.rc.right = data.rc.left + (int)Math.Round(actualSize.X);//左对齐
340             else if (Location == AppBarLocation.Right)
341                 data.rc.left = data.rc.right - (int)Math.Round(actualSize.X);//右对齐
342         }
343         //调整完毕，设置为最终位置
344         Interop.SHAppBarMessage((int)Interop.AppBarMsg.ABM_SETPOS, ref data);
345         //应用到窗口
346         var location = toWpfUnit.Transform(new Point(data.rc.left, data.rc.top));
347         var dimension = toWpfUnit.Transform(new Vector(data.rc.right - data.rc.left,
348                                                                                     data.rc.bottom - data.rc.top));
349         var rect = new Rect(location, new Size(dimension.X, dimension.Y));
350         DockedSize = rect;
351 
352         _window.Dispatcher.Invoke(DispatcherPriority.ApplicationIdle, () =>{ 
353         _window.Left = rect.Left;
354         _window.Top = rect.Top;
355         _window.Width = rect.Width;
356         _window.Height = rect.Height;
357         });
358 
359         Debug.WriteLine("Set {0} Left: {1} ,Top: {2}, Width: {3}, Height: {4}", _window.Title, _window.Left, _window.Top, _window.Width, _window.Height);
360     }
361     public void DisableAppBar()
362     {
363         if (_isRegistered)
364         {
365             _isRegistered = false;
366             var data = new Interop.APPBARDATA();
367             data.cbSize = Marshal.SizeOf(data);
368             data.hWnd = _hWnd;
369             data.uCallbackMessage = _callbackId;
370             Interop.SHAppBarMessage((int)Interop.AppBarMsg.ABM_REMOVE, ref data);
371             _isRegistered = false;
372             RestoreWindowInfo();
373             Debug.WriteLine(_window.Title + " DisableAppBar");
374         }
375     }
376 }
377 
378 public enum AppBarLocation : int
379 {
380     Left = 0,
381     Top,
382     Right,
383     Bottom,
384     None,
385     RegisterOnly=99
386 }
387 
388 internal static class Interop
389 {
390     #region Structures & Flags
391     [StructLayout(LayoutKind.Sequential)]
392     internal struct RECT
393     {
394         public int left;
395         public int top;
396         public int right;
397         public int bottom;
398     }
399 
400     [StructLayout(LayoutKind.Sequential)]
401     internal struct APPBARDATA
402     {
403         public int cbSize;
404         public IntPtr hWnd;
405         public int uCallbackMessage;
406         public int uEdge;
407         public RECT rc;
408         public IntPtr lParam;
409     }
410 
411     internal enum AppBarMsg : int
412     {
413         ABM_NEW = 0,
414         ABM_REMOVE,
415         ABM_QUERYPOS,
416         ABM_SETPOS,
417         ABM_GETSTATE,
418         ABM_GETTASKBARPOS,
419         ABM_ACTIVATE,
420         ABM_GETAUTOHIDEBAR,
421         ABM_SETAUTOHIDEBAR,
422         ABM_WINDOWPOSCHANGED,
423         ABM_SETSTATE
424     }
425     internal enum AppBarNotify : int
426     {
427         ABN_STATECHANGE = 0,
428         ABN_POSCHANGED,
429         ABN_FULLSCREENAPP,
430         ABN_WINDOWARRANGE
431     }
432     #endregion
433 
434     #region Win32 API
435     [DllImport("SHELL32", CallingConvention = CallingConvention.StdCall)]
436     internal static extern uint SHAppBarMessage(int dwMessage, ref APPBARDATA pData);
437 
438     [DllImport("User32.dll", CharSet = CharSet.Auto)]
439     internal static extern int RegisterWindowMessage(string msg);
440     #endregion
441 }

三、已知问题

1.在我的github上的实例程序中，如果你将两个同进程的窗口并排叠放的话，会导致explorer和你的进程双双爆栈，windows似乎不能很好地处理这两个并排放置的窗口，一直在左右调整位置，疯狂发送ABN_POSCHANGED消息。(快去clone试试，死机了不要打我) 但是并排放置示例窗口和OneNote的Dock窗口就没有问题。

2.计算停靠窗口时，如果选择停靠位置为Bottom，则系统建议的bottom位置值会比实际的高，测试发现是任务栏窗口占据了部分空间，应该是预留给平板模式的更大图标任务栏（猜测，很不合理的设计）