c# - 如何在 .NET c# 中使用 Win32 GetMonitorInfo()？

Question

我必须实现一个保存窗口最后位置的功能。当应用程序启动时，需要获取并恢复这个位置。

现在可能是拆除了第二台显示器。如果最后一个位置在现在不可见的监视器上(换句话说，保存的坐标在可见坐标之外)，则应捕获这种情况并将坐标设置为默认位置而不是最后一个位置。

为了检索有关监视器的信息，我需要使用 Win32。完成这项工作对我来说并不容易。

我创建了一个 Helper 类:

public static class DisplayHelper
    {
        private const int MONITOR_DEFAULTTONEAREST = 2;

        [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
        public static extern int GetSystemMetrics(int nIndex);

        [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
        private static extern UInt32 MonitorFromPoint(Point pt, UInt32 dwFlags);

        [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
        private static extern bool GetMonitorInfo(UInt32 monitorHandle, ref MonitorInfo mInfo);


        public static void GetMonitorInfoNow(MonitorInfo mi, Point pt)
        {
            UInt32 mh = MonitorFromPoint(pt, 0);
            mi.cbSize = (UInt32)System.Runtime.InteropServices.Marshal.SizeOf(typeof(MonitorInfo));
            mi.dwFlags = 0;
            bool result = GetMonitorInfo(mh, ref mi);

        }
    }

这些是我创建 MonitorInfo 和 Rect 类的尝试:

[StructLayout(LayoutKind.Sequential)]
    public class MonitorInfo
    {
        public UInt32 cbSize;
        public Rectangle2 rcMonitor;
        public Rectangle2 rcWork;
        public UInt32 dwFlags;

        public MonitorInfo()
        {
            rcMonitor = new Rectangle2();
            rcWork = new Rectangle2();

            cbSize = (UInt32)System.Runtime.InteropServices.Marshal.SizeOf(typeof(MonitorInfo));
            dwFlags = 0;
        }
    }

    [StructLayout(LayoutKind.Sequential)]
    public class Rectangle2
    {
        public UInt64 left;
        public UInt64 top;
        public UInt64 right;
        public UInt64 bottom;

        public Rectangle2()
        {
            left = 0;
            top = 0;
            right = 0;
            bottom = 0;
        }
    }

我正在使用这样的代码来获取可见监视器:

//80 means it counts only visible display monitors.
int lcdNr = DisplayHelper.GetSystemMetrics(80);
var point = new System.Drawing.Point((int) workSpaceWindow.Left, (int) workSpaceWindow.Top);
MonitorInfo monitorInfo = new MonitorInfo();
DisplayHelper.GetMonitorInfoNow(monitorInfo, point);

最后一个方法在尝试执行时抛出异常

bool result = GetMonitorInfo(mh, ref mi);

有什么建议可以解决这个问题吗？

Answer 1

与其调用 native API，不如使用 System.Windows.Forms.Screen .它应该拥有您需要的一切，并且更易于使用。

Screen.FromPoint是具有 MONITOR_DEFAULTTONEAREST 选项的 GetMonitorInfoNow 函数的托管等效项。我只是注意到您没有使用该选项，因此您可能必须自己编写或使用正确的 P/Invoke 签名。

如果您只引用 System.Drawing 和 System.Windows.Forms，编写您自己的应该相当简单。这两个都应该有效:

static Screen ScreenFromPoint1(Point p)
{
    System.Drawing.Point pt = new System.Drawing.Point((int)p.X, (int)p.Y);
    return Screen.AllScreens
                    .Where(scr => scr.Bounds.Contains(pt))
                    .FirstOrDefault();
}

static Screen ScreenFromPoint2(Point p)
{
    System.Drawing.Point pt = new System.Drawing.Point((int)p.X, (int)p.Y);
    var scr = Screen.FromPoint(pt);
    return scr.Bounds.Contains(pt) ? scr : null;
}

如果您更喜欢自己进行 Win32 调用，则需要调用的函数的正确 P/Invoke 签名(即您从反编译 .Net DLL 中获得的签名)是:

    [DllImport("User32.dll", CharSet=CharSet.Auto)] 
    public static extern bool GetMonitorInfo(HandleRef hmonitor, [In, Out]MONITORINFOEX info);
    [DllImport("User32.dll", ExactSpelling=true)]
    public static extern IntPtr MonitorFromPoint(POINTSTRUCT pt, int flags);

    [StructLayout(LayoutKind.Sequential,CharSet=CharSet.Auto, Pack=4)]
    public class MONITORINFOEX { 
        public int     cbSize = Marshal.SizeOf(typeof(MONITORINFOEX));
        public RECT    rcMonitor = new RECT(); 
        public RECT    rcWork = new RECT(); 
        public int     dwFlags = 0;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst=32)] 
        public char[]  szDevice = new char[32];
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct POINTSTRUCT { 
        public int x;
        public int y;
        public POINTSTRUCT(int x, int y) {
          this.x = x; 
          this.y = y;
        } 
    } 

    [StructLayout(LayoutKind.Sequential)] 
    public struct RECT {
        public int left; 
        public int top; 
        public int right;
        public int bottom; 
    }