c# - 在多个显示器上绘制所有窗口

Question

我正在使用以下代码在单个显示器上绘图:

Point cursorLocation;
NativeMethods.GetCursorPos(out cursorLocation);
Screen screen = Screen.FromPoint(cursorLocation);

Point h1 = new Point(screen.Bounds.Left, cursorLocation.Y);
Point h2 = new Point(screen.Bounds.Right, cursorLocation.Y);
Point v1 = new Point(cursorLocation.X, screen.Bounds.Top);
Point v2 = new Point(cursorLocation.X, screen.Bounds.Bottom);

using (Graphics graphics = Graphics.FromHwnd(NativeMethods.GetDesktopWindow())) {
    NativeMethods.SHChangeNotify(0x8000000, 0x1000, IntPtr.Zero, IntPtr.Zero);
    graphics.DrawLine(Pens.Red, h1, h2);
    graphics.DrawLine(Pens.Red, v1, v2);
}

从本质上讲，这应该理论上在任一显示器上绘制。但是，它仅利用初级。因此，为了解决这个问题，我正在获取所有显示器的 DC 并尝试以这种方式进行。

IntPtr hdc = NativeMethods.CreateDC("DISPLAY", IntPtr.Zero, IntPtr.Zero, IntPtr.Zero);
Graphics graphics = Graphics.FromHdc(hdc);
graphics.DrawLine(Pens.Red, h1, h2);
graphics.DrawLine(Pens.Red, v1, v2);
graphics.Dispose();
NativeMethods.ReleaseDC(IntPtr.Zero, hdc);

看吧，这根本就没有绘制到屏幕上。我为 CreateDC 尝试了各种重载，并搜索了 SO 和其他资源，但我很困惑。

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解决此问题后，有人知道如何使用 SHChangeNotify 刷新桌面来消除闪烁吗？我只画了两条线，它像疯了一样闪烁..)

Answer 1

这对我有用。我使用 EnumDisplayDevices 来获取名称。

[DllImport("gdi32.dll")]
public static extern IntPtr CreateDC(string lpszDriver, string lpszDevice, string lpszOutput, IntPtr lpInitData);

var hdc = CreateDC(@"\\.\DISPLAY1", "", "", IntPtr.Zero);
Graphics g = Graphics.FromHdc(hdc);
var pt = Cursor.Position;
g.DrawEllipse(Pens.BlueViolet, pt.X - 100, pt.Y - 100, 200, 200);

更多信息在这里: http://msdn.microsoft.com/en-us/library/windows/desktop/dd145179(v=vs.85).aspx