【发布时间】：2014-02-28 19:17:04
【问题描述】：
我的 WPF 应用程序在我的两台显示器笔记本电脑开发系统上表现出奇怪的行为。第二台显示器的分辨率为 1920 x 1080；笔记本电脑的分辨率为 1366 x 768。笔记本电脑运行的是 Windows 8.1，两个显示器的 DPI 设置都设置为 100%。插入后，第二台显示器就是主显示器。显然，当第二台显示器没有插入时，笔记本电脑的显示器就是主显示器。
应用程序窗口总是最大化，但可以最小化。无法拖动 问题与插入或拔下第二台显示器时窗口从一台显示器移动到另一台显示器时的显示方式有关。
当程序在插入第二台显示器的情况下启动时，它会在拔下时移至笔记本电脑的显示屏。 WPF 代码也可以正确处理此更改。也就是说，它检测到原始尺寸不适合新显示器，因此会重新绘制以适应新显示器。当第二台显示器重新插入时，它会移回第二台显示器并以适合该显示器的大小重新绘制自己。这正是我在这种情况下想要的。问题是当程序在其他配置中启动时。
当程序在没有插入第二台显示器的情况下启动时，它会以适合笔记本电脑显示器的尺寸绘制。当第二个监视器插入并运行程序时，窗口移动到第二个监视器，但绘制错误。由于程序已最大化，它的三边都有一个巨大的黑色边框，内容显示在与笔记本电脑显示屏相同大小的区域中。
编辑： 我刚刚完成了一些测试，WPF 似乎无法正确处理从更小分辨率到更高分辨率的分辨率变化。该窗口的行为与我在笔记本电脑的显示屏上启动程序然后插入第二台显示器时所得到的行为相同。至少它是一致的。
我发现我可以通过处理SystemEvents.DisplaySettingsChanged 事件来获得第二台显示器何时插入或屏幕分辨率更改的通知。在我的测试中，我发现当窗口从较小的显示屏移动到较大的显示屏时，Width、Height、ActualWidth 和ActualHeight 在窗口移动到较大的显示屏时没有变化窗户。我能做的最好的事情是将Height 和Width 属性设置为与监视器的工作区域匹配的值，但ActualWidth 和ActualHeight 属性不会改变。
如何强制窗口将我的问题案例视为只是分辨率更改？或者，如何强制窗口将其ActualWidth 和ActualHeight 属性更改为正确的值？
该窗口源自我编写的名为 DpiAwareWindow 的类：
public class DpiAwareWindow : Window {
private const int LOGPIXELSX = 88;
private const int LOGPIXELSY = 90;
private const int MONITOR_DEFAULTTONEAREST = 0x00000002;
protected enum MonitorDpiType {
MDT_Effective_DPI = 0,
MDT_Angular_DPI = 1,
MDT_Raw_DPI = 2,
MDT_Default = MDT_Effective_DPI
}
public Point CurrentDpi { get; private set; }
public bool IsPerMonitorEnabled;
public Point ScaleFactor { get; private set; }
protected HwndSource source;
protected Point systemDpi;
protected Point WpfDpi { get; set; }
public DpiAwareWindow()
: base() {
// Watch for SystemEvent notifications
SystemEvents.DisplaySettingsChanged += SystemEvents_DisplaySettingsChanged;
// Set up the SourceInitialized event handler
SourceInitialized += DpiAwareWindow_SourceInitialized;
}
~DpiAwareWindow() {
// Deregister our SystemEvents handler
SystemEvents.DisplaySettingsChanged -= SystemEvents_DisplaySettingsChanged;
}
private void DpiAwareWindow_SourceInitialized( object sender, EventArgs e ) {
source = (HwndSource) HwndSource.FromVisual( this );
source.AddHook( WindowProcedureHook );
// Determine if this application is Per Monitor DPI Aware.
IsPerMonitorEnabled = GetPerMonitorDPIAware() == ProcessDpiAwareness.Process_Per_Monitor_DPI_Aware;
// Is the window in per-monitor DPI mode?
if ( IsPerMonitorEnabled ) {
// It is. Calculate the DPI used by the System.
systemDpi = GetSystemDPI();
// Calculate the DPI used by WPF.
WpfDpi = new Point {
X = 96.0 * source.CompositionTarget.TransformToDevice.M11,
Y = 96.0 * source.CompositionTarget.TransformToDevice.M22
};
// Get the Current DPI of the monitor of the window.
CurrentDpi = GetDpiForHwnd( source.Handle );
// Calculate the scale factor used to modify window size, graphics and text.
ScaleFactor = new Point {
X = CurrentDpi.X / WpfDpi.X,
Y = CurrentDpi.Y / WpfDpi.Y
};
// Update Width and Height based on the on the current DPI of the monitor
Width = Width * ScaleFactor.X;
Height = Height * ScaleFactor.Y;
// Update graphics and text based on the current DPI of the monitor.
UpdateLayoutTransform( ScaleFactor );
}
}
protected Point GetDpiForHwnd( IntPtr hwnd ) {
IntPtr monitor = MonitorFromWindow( hwnd, MONITOR_DEFAULTTONEAREST );
uint newDpiX = 96;
uint newDpiY = 96;
if ( GetDpiForMonitor( monitor, (int) MonitorDpiType.MDT_Effective_DPI, ref newDpiX, ref newDpiY ) != 0 ) {
return new Point {
X = 96.0,
Y = 96.0
};
}
return new Point {
X = (double) newDpiX,
Y = (double) newDpiY
};
}
public static ProcessDpiAwareness GetPerMonitorDPIAware() {
ProcessDpiAwareness awareness = ProcessDpiAwareness.Process_DPI_Unaware;
try {
Process curProcess = Process.GetCurrentProcess();
int result = GetProcessDpiAwareness( curProcess.Handle, ref awareness );
if ( result != 0 ) {
throw new Exception( "Unable to read process DPI level" );
}
} catch ( DllNotFoundException ) {
try {
// We're running on either Vista, Windows 7 or Windows 8. Return the correct ProcessDpiAwareness value.
awareness = IsProcessDpiAware() ? ProcessDpiAwareness.Process_System_DPI_Aware : ProcessDpiAwareness.Process_DPI_Unaware;
} catch ( EntryPointNotFoundException ) { }
} catch ( EntryPointNotFoundException ) {
try {
// We're running on either Vista, Windows 7 or Windows 8. Return the correct ProcessDpiAwareness value.
awareness = IsProcessDpiAware() ? ProcessDpiAwareness.Process_System_DPI_Aware : ProcessDpiAwareness.Process_DPI_Unaware;
} catch ( EntryPointNotFoundException ) { }
}
// Return the value in awareness.
return awareness;
}
public static Point GetSystemDPI() {
IntPtr hDC = GetDC( IntPtr.Zero );
int newDpiX = GetDeviceCaps( hDC, LOGPIXELSX );
int newDpiY = GetDeviceCaps( hDC, LOGPIXELSY );
ReleaseDC( IntPtr.Zero, hDC );
return new Point {
X = (double) newDpiX,
Y = (double) newDpiY
};
}
public void OnDPIChanged() {
ScaleFactor = new Point {
X = CurrentDpi.X / WpfDpi.X,
Y = CurrentDpi.Y / WpfDpi.Y
};
UpdateLayoutTransform( ScaleFactor );
}
public virtual void SystemEvents_DisplaySettingsChanged( object sender, EventArgs e ) {
// Get the handle for this window. Need to worry about a window that has been created by not yet displayed.
IntPtr handle = source == null ? new HwndSource( new HwndSourceParameters() ).Handle : source.Handle;
// Get the current DPI for the window we're on.
CurrentDpi = GetDpiForHwnd( handle );
// Adjust the scale factor.
ScaleFactor = new Point {
X = CurrentDpi.X / WpfDpi.X,
Y = CurrentDpi.Y / WpfDpi.Y
};
// Update the layout transform
UpdateLayoutTransform( ScaleFactor );
}
private void UpdateLayoutTransform( Point scaleFactor ) {
if ( IsPerMonitorEnabled ) {
if ( ScaleFactor.X != 1.0 || ScaleFactor.Y != 1.0 ) {
LayoutTransform = new ScaleTransform( scaleFactor.X, scaleFactor.Y );
} else {
LayoutTransform = null;
}
}
}
public virtual IntPtr WindowProcedureHook( IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled ) {
// Determine which Monitor is displaying the Window
IntPtr monitor = MonitorFromWindow( hwnd, MONITOR_DEFAULTTONEAREST );
// Switch on the message.
switch ( (WinMessages) msg ) {
case WinMessages.WM_DPICHANGED:
// Marshal the value in the lParam into a Rect.
RECT newDisplayRect = (RECT) Marshal.PtrToStructure( lParam, typeof( RECT ) );
// Set the Window's position & size.
Vector ul = source.CompositionTarget.TransformFromDevice.Transform( new Vector( newDisplayRect.left, newDisplayRect.top ) );
Vector hw = source.CompositionTarget.TransformFromDevice.Transform( new Vector( newDisplayRect.right = newDisplayRect.left, newDisplayRect.bottom - newDisplayRect.top ) );
Left = ul.X;
Top = ul.Y;
Width = hw.X;
Height = hw.Y;
// Remember the current DPI settings.
Point oldDpi = CurrentDpi;
// Get the new DPI settings from wParam
CurrentDpi = new Point {
X = (double) ( wParam.ToInt32() >> 16 ),
Y = (double) ( wParam.ToInt32() & 0x0000FFFF )
};
if ( oldDpi.X != CurrentDpi.X || oldDpi.Y != CurrentDpi.Y ) {
OnDPIChanged();
}
handled = true;
return IntPtr.Zero;
case WinMessages.WM_GETMINMAXINFO:
// lParam has a pointer to the MINMAXINFO structure. Marshal it into managed memory.
MINMAXINFO mmi = (MINMAXINFO) Marshal.PtrToStructure( lParam, typeof( MINMAXINFO ) );
if ( monitor != IntPtr.Zero ) {
MONITORINFO monitorInfo = new MONITORINFO();
GetMonitorInfo( monitor, monitorInfo );
// Get the Monitor's working area
RECT rcWorkArea = monitorInfo.rcWork;
RECT rcMonitorArea = monitorInfo.rcMonitor;
// Adjust the maximized size and position to fit the work area of the current monitor
mmi.ptMaxPosition.x = Math.Abs( rcWorkArea.left - rcMonitorArea.left );
mmi.ptMaxPosition.y = Math.Abs( rcWorkArea.top - rcMonitorArea.top );
mmi.ptMaxSize .x = Math.Abs( rcWorkArea.right - rcWorkArea.left );
mmi.ptMaxSize .y = Math.Abs( rcWorkArea.bottom - rcWorkArea.top );
}
// Copy our changes to the mmi object back to the original
Marshal.StructureToPtr( mmi, lParam, true );
handled = true;
return IntPtr.Zero;
default:
// Let the WPF code handle all other messages. Return 0.
return IntPtr.Zero;
}
}
[DllImport( "user32.dll", CallingConvention = CallingConvention.StdCall )]
protected static extern IntPtr GetDC( IntPtr hWnd );
[DllImport( "gdi32.dll", CallingConvention = CallingConvention.StdCall )]
protected static extern int GetDeviceCaps( IntPtr hDC, int nIndex );
[DllImport( "shcore.dll", CallingConvention = CallingConvention.StdCall )]
protected static extern int GetDpiForMonitor( IntPtr hMonitor, int dpiType, ref uint xDpi, ref uint yDpi );
[DllImport( "user32" )]
protected static extern bool GetMonitorInfo( IntPtr hMonitor, MONITORINFO lpmi );
[DllImport( "shcore.dll", CallingConvention = CallingConvention.StdCall )]
protected static extern int GetProcessDpiAwareness( IntPtr handle, ref ProcessDpiAwareness awareness );
[DllImport( "user32.dll", CallingConvention = CallingConvention.StdCall )]
protected static extern bool IsProcessDpiAware();
[DllImport( "user32.dll", CallingConvention = CallingConvention.StdCall )]
protected static extern IntPtr MonitorFromWindow( IntPtr hwnd, int flag );
[DllImport( "user32.dll", CallingConvention = CallingConvention.StdCall )]
protected static extern void ReleaseDC( IntPtr hWnd, IntPtr hDC );
}
public enum SizeMessages {
SIZE_RESTORED = 0,
SIZE_MINIMIZED = 1,
SIZE_MAXIMIZED = 2,
SIZE_MAXSHOW = 3,
SIZE_MAXHIDE = 4
}
public enum WinMessages : int {
WM_DPICHANGED = 0x02E0,
WM_GETMINMAXINFO = 0x0024,
WM_SIZE = 0x0005,
WM_WINDOWPOSCHANGING = 0x0046,
WM_WINDOWPOSCHANGED = 0x0047,
}
public enum ProcessDpiAwareness {
Process_DPI_Unaware = 0,
Process_System_DPI_Aware = 1,
Process_Per_Monitor_DPI_Aware = 2
}
我认为问题不在于这段代码；我认为它在 WPF Window 类中。我需要找到一种方法来解决这个问题。但是，我可能是错的。
编辑：
我有一个测试程序，其中包含一个从我的DpiAwareWindow 类下降的普通窗口。当屏幕分辨率发生变化时，它会表现出类似的行为。但是，作为测试，我更改了代码，使窗口从 Window 类下降，我没有看到行为。所以DpiAwareWindow 代码中有些东西不起作用。
如果问得不算多，有 VS 2013 的人可以下载this WPF Per Monitor DPI Aware sample program，构建它并查看它在以较低的屏幕分辨率启动然后增加屏幕分辨率时是否正常运行？
编辑 2
我刚刚做了一些测试，我发现如果我在WindowProcedureHook 方法的switch 语句中注释掉整个WinMessages.WM_GETMINMAXINFO 案例，问题就不会发生。此代码的目的是限制最大化窗口的大小，使其不会遮挡任务栏。
添加此代码是为了防止最大化的窗口遮挡任务栏。当屏幕分辨率发生变化时，它返回的内容与 WPF 中运行的任何逻辑之间似乎存在某种交互。
【问题讨论】：
-
是的，我有并且我正在使用该事件来检测更改。问题似乎是当新屏幕分辨率大于旧屏幕分辨率时，窗口内容的大小不会增加。就好像子控件的
MaxHeight和MaxWidth属性固定在较小的分辨率上，而我尝试过的任何东西都没有改变它们。我什至遍历了整个可视化树并在每个上都调用了InvalidateMeasure，但没有运气。 -
有趣，可能是一个错误。当事件触发时，您是否能够检测到正确的分辨率？
-
是的，我可以在事件触发时获得正确的屏幕分辨率。我想更正我之前的评论。窗口及其子控件的
MaxHeight和MaxWidth均保持不变。窗口及其子控件的ActualWidth是正确的。这是不会改变的窗口的ActualHeight。我遍历了所有子控件并调用了InvalidateMeasure和InvalidateArrage，然后在完成后调用了UpdateLayout，并且布局没有任何变化。ActualHeight拒绝更改。 -
我已经确认当
MainWindow从 Window 下降时一切正常。无论问题是什么，它都存在于 DPI 感知代码中。