C# C.WinApi。在窗户上画

我需要写一个C程序来识别光标下的窗口，并在上面画一个边框

我可以很容易地得到一个windows处理程序：

...
Point point;
WinApi.GetCursorPos(out point);
WinApi.WindowFromPoint(point);
...

但我不能在那扇窗户上画画

public static void drawSelectionRectangle(IntPtr handler)
{
    Rectangle rectangle;
    WinApi.GetWindowRect(handler, out rectangle);

    WinApi.PAINTSTRUCT paintProperties;
    IntPtr paintContext = WinApi.BeginPaint(handler, out paintProperties);

    IntPtr pen = WinApi.CreatePen(WinApi.PenStyle.PS_SOLID, 5, (uint) ColorTranslator.ToWin32(Color.Red));
    WinApi.SelectObject(paintContext, pen);

    WinApi.Rectangle(paintContext, rectangle.Left, rectangle.Top, rectangle.Right, rectangle.Bottom);

    WinApi.ValidateRect(handler, IntPtr.Zero);
    WinApi.EndPaint(handler, ref paintProperties);
}

我调用了drawSelectionRectangleIntPtr处理程序一次，方法是通过MyForm的onPaint方法单击按钮并循环，而不是在我想要绘制的表单上。这似乎不起作用

---

请帮帮我。我不知道该怎么办。

这不是我问题的完全解决方案，但它是有效的

我想在目标窗口上绘制，若目标窗口位于其他窗口下，边框也必须位于其他窗口下……但当边框在所有窗口上绘制时，这是一个比没有更好的解决方案

我希望我的问题和解决方案能帮助别人。谢谢大家

public partial class Form1 : Form
{
    private IntPtr selectedWindowHandler;    

    ...

    private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {
        Cursor.Current = new Cursor(Properties.Resources.aimImage.GetHicon());
        mousePressed = true;
        pictureBox_aimImage.Invalidate();
    }

    private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
    { 
        mousePressed = false;
        invalidateAllWindows();
    }

    // this method for pictureBox1 which contain custom cursor
    // to choose window for draw border you must click on this box 
    // and drag to targwt window
    private void pictureBox1_Paint(object sender, PaintEventArgs e)
    {
        if (mousePressed)
        {
            Point point;
            WinApi.GetCursorPos(out point);
            IntPtr hWnd = Window.getHandler(point);

            if (hWnd.Equals(selectedWindowHandler))
            {                    
                drawSelectionRectangle(selectedWindowHandler);
                pictureBox_aimImage.Invalidate();
            } else
            {
                selectedWindowHandler = hWnd;
                invalidateAllWindows();
            }
        }
    }

    // when i once called InvalidateRect(...) not all border was cleared
    // i don't know why
    private static void invalidateAllWindows()
    {
        WinApi.InvalidateRect(IntPtr.Zero, IntPtr.Zero, true);
        WinApi.InvalidateRect(IntPtr.Zero, IntPtr.Zero, true);
        WinApi.InvalidateRect(IntPtr.Zero, IntPtr.Zero, true);
    }     

    ...

    public static Rectangle getRectangle(IntPtr handler)
    {
        Rectangle rectangle;
        WinApi.GetWindowRect(handler, out rectangle);
        rectangle = new Rectangle(
            rectangle.Location,
            new Size(
                rectangle.Size.Width - rectangle.Location.X,
                rectangle.Size.Height - rectangle.Location.Y
            )
        );
        return rectangle;
    }

    public static void drawSelectionRectangle(IntPtr handler)
    {           
        //getting target window rectangle for GDI+
        Rectangle rect = getRectangle(handler);

        //getting context of desktop
        Graphics g = Graphics.FromHwnd(IntPtr.Zero);
        using (g)
        {
            //drawing borders
            g.DrawRectangle(new Pen(Color.Red, 3), rect);
        }
    }

}

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不去上班。窗户不是你的。所有者将在你可能成功绘制的任何东西上绘制。您需要了解Win32绘画是如何工作的。不管问题是什么，这都不是解决办法。